Aspect Ratio Calculator – Resize Images and Video Without Stretching
Type in 1920 × 1080 and this page answers 16:9.
Your image or video size
Try a common ratio
Or a common size
Resize it — keep the shape
🔒 Everything is calculated in your browser — your numbers never leave your device.
Advanced options — print size at any DPI, and resize by percentage
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Applying sets the new width from the percentage and the calculator fills in the matching height, keeping the shape.
The print size below is already worked out from the image size above at the DPI shown — open Advanced options to change the DPI or to resize by a percentage.
Print size at any DPI, and resize by percentage are already included in the result with their default values — open Advanced options to change them.
Your aspect ratio
The full picture
Resize, same shape
What this shape is
16:9, landscape — the widescreen standard. Nearly every TV, monitor, laptop and online video uses this shape, so a frame resized here drops into any of them without black bars. Its diagonal of 2,203 px is pure Pythagoras: the square root of width squared plus height squared.
Nearest pixel, honestly: screens and image files only hold whole pixels, so a resized side of 666.67 px is stored as 667. The shape shifts by a third of a pixel — invisible in any real image — and this page always shows the exact figure next to the rounded one.
Type in 1920 × 1080 and this page answers 16:9 — then tells you the exact height that keeps that shape at any new width, down to the pixel. It simplifies ratios with exact greatest-common-divisor arithmetic, never a rounded decimal, counts the pixels and megapixels, measures the diagonal, and draws the original and the resize on one shared scale so you can see the new shape before you make it.
Key takeaways
- An aspect ratio is width divided by height, simplified with exact greatest-common-divisor arithmetic, never a rounded decimal.
- 1366 × 768 is not 16:9: it simplifies to 683:384, a decimal of 1.7786 against 16:9’s 1.7778.
- Print size is pixels divided by DPI, so the same image prints at very different sizes at 72, 150 and 300 DPI.
Contents
- Both rectangles, one honest scale
- How it works, in 3 steps
- The arithmetic behind it
- Deep dives
- Common ratios: social, print, screen and cinema
- Print size and DPI: the same pixels, three different prints
- Resizing with the shape locked, and the rounding problem
- Diagonal, megapixels and what they do not tell you
- Aspect ratio questions, answered
Both rectangles, one honest scale
The original frame and its resize, drawn with a single shared scale. If the twin has the same shape as the original, the resize kept the ratio — a stretch or a squash would be visible at a glance. The diagonal drawn on the original is the corner-to-corner measure your screen’s inch size comes from, here in pixels.
1,920 × 1,080 resized to 1,280 × 720 px — same 16:9 shape, at 66.67% of the width.
Why one shared scale matters
Two rectangles drawn at different scales can make any resize look right. Here both frames share a single scale, so a stretched or squashed result would show immediately — and the proportions stay truthful whatever you enter: portrait frames stand tall, squares stay square, and an ultrawide stretches long and low. The picture is drawn from the same numbers as the answers above, never from a stock diagram.
How it works, in 3 steps
Enter the size you have
Width and height in pixels — from an image’s properties, a video export setting or a screen’s resolution. Any size works, from a 32 × 32 icon to an 8K frame.
Read the exact ratio
Both sides are divided by their greatest common divisor, so 1,920 × 1,080 becomes 16:9 exactly — and 1,366 × 768 honestly becomes 683:384, because that panel is not quite 16:9.
Resize by one side only
Give a new width or a new height and the other side is solved from the ratio, then rounded to the nearest whole pixel with the exact figure beside it. The shape never stretches.
The arithmetic behind it
The default, worked through. 1,920 × 1,080: the greatest common divisor of 1,920 and 1,080 is 120. Divide both sides — 1,920 ÷ 120 = 16 and 1,080 ÷ 120 = 9 — and the ratio is 16:9. The frame holds 1,920 × 1,080 = 2,073,600 pixels (2.07 MP), and its diagonal is √(1,920² + 1,080²) = 2,202.9 px, shown rounded as 2,203.
The laptop that is not quite 16:9. A 1,366 × 768 screen shares a GCD of only 2, so its exact ratio is 683:384 — 1.7786:1 against 16:9’s 1.7778:1. The difference is about a twentieth of a percent, which is why it is sold as 16:9; but resize it with 16:9 maths and a 1,000 px width predicts a height of 562.5 px, where the panel’s true shape needs 562.23. That fraction-of-a-pixel disagreement is exactly what this page avoids by never assuming the ratio — it always works from the pixels you actually have.
A photo and a target width. A 4,000 × 3,000 photo is exactly 4:3 (GCD 1,000). Set it 1,000 px wide for a web page and the height is 1,000 × (3,000 ÷ 4,000) = 750 px exactly — no rounding, no crop. On a 3:2 frame the same 1,000 px width lands on 666.67 px, which is why the resize box always shows the exact figure beside the whole pixel a file can actually hold.
Deep dives
A single number is easier to print on a box than two. Since the CRT era, screens have been sold by their diagonal in inches — one figure that sounds bigger than either side alone and lets a whole range line up on a shelf: 24, 27, 32, 55. The catch is that the diagonal alone says nothing about shape or sharpness. A 27-inch 16:9 panel is really 23.5 × 13.2 inches of glass; a 27-inch ultrawide is longer and shorter, and a 27-inch 4K screen holds four times the pixels of a 27-inch 1080p one.
The fix is to think in the pair, not the diagonal. Width and height in pixels give you the aspect ratio, the pixel count, and — divided into the physical diagonal — the pixel density that decides how sharp text looks. That is why this page reports the diagonal in pixels as well: 2,203 px across a 15.6-inch laptop panel is dense and crisp; the same count across a 55-inch TV is a very different picture, and now you can compare the two honestly.
Show a wide film on a narrower screen and something has to give. A cinema frame at 2.39:1 fitted to a 1,920 × 1,080 screen by width uses only 1,920 ÷ 2.39 = 803 px of height, leaving about 138 px of black bar at the top and the same at the bottom — the letterbox. Run it the other way, a 4:3 photo on a 16:9 screen, and the picture stands 1,080 px tall and 1,440 px wide, with a 240 px pillar bar on each side.
The alternative to bars is the crop, and the crop is not free. Fill that 16:9 screen with the 4:3 photo and the photo must scale to 1,920 px wide — which makes it 1,440 px tall, so 180 px vanish from the top and 180 from the bottom: a quarter of the photograph, gone. Bars keep everything and waste screen; cropping fills the screen and wastes picture. Resizing with this page never does either silently — it keeps the shape you started with, which is the one decision that loses nothing.
Common ratios: social, print, screen and cinema
The calculator’s job is to reduce any size to its exact ratio, but most work starts from a ratio somebody else chose: a platform, a printer or a cinema. The table below collects the ratios you are most likely to be asked for, with a real size for each, so you can check a brief against a number instead of a name. Every ratio in the table was reduced with the same greatest-common-divisor arithmetic the calculator uses, which is why two of the entries carry a correction to what their marketing names suggest.
| Ratio | Example size | Used for |
|---|---|---|
| 1:1 | 1080 × 1080 | Square feed posts and profile images |
| 4:5 | 1080 × 1350 | Portrait feed posts, the tallest a feed allows without cropping |
| 9:16 | 1080 × 1920 | Stories, reels and vertical video |
| 16:9 | 1920 × 1080 | Video, television and most monitors |
| 4:3 | 1600 × 1200 | Classic television, older monitors and compact cameras |
| 3:2 | 1500 × 1000 | 35 mm photography and many DSLR sensors |
| 16:10 | 1920 × 1200 | Widescreen monitors with extra vertical room |
| 1.91:1 | 1200 × 628 | Link preview images on social platforms |
| 2.39:1 | 2048 × 858 | CinemaScope widescreen cinema |
| 1:1.414 | 210 × 297 mm | A-series paper, A4 included, where each size halves the last |
Ultrawide monitors deserve a footnote, because their marketed ratio is not their exact ratio. A 2560 × 1080 monitor simplifies to 64:27, a decimal of 2.370, while a 3440 × 1440 monitor simplifies to 43:18, a decimal of 2.389. Both are sold as 21:9, whose decimal is 2.333, and neither is exactly that: the marketing name is a family label, not a measurement. If a design brief says 21:9, ask which pixel size it means, because the two ultrawide sizes differ from each other by enough to shift a layout. The same honesty applies to the laptop size 1366 × 768, which this page’s own FAQ addresses: it simplifies to 683:384, decimal 1.7786, against 16:9’s 1.7778. The difference is about five hundredths of a percent, invisible on screen, but it is real, and a tool that rounded it to 16:9 would be lying about its own arithmetic.
Orientation follows from the comparison, not from a label: width greater than height is landscape, height greater than width is portrait, and equal sides are square. A 9:16 video is the same shape as a 16:9 video turned on its side, and rotating an image swaps the two numbers without changing the shape’s family. That is why the calculator reports orientation alongside the ratio: a brief that asks for portrait 16:9 usually means 9:16, and the swap is the most common ratio mistake in production work.
Print size and DPI: the same pixels, three different prints
DPI means dots per inch, and in print arithmetic it is simply the divisor: print width in inches is pixel width divided by DPI, and print height is pixel height divided by DPI. The Advanced options panel above does that division live for your image at any DPI you enter. The table below does it for the calculator’s default image, 1920 × 1080, at the three DPI values you will meet most often, plus two larger photographs at the standard photo-print resolution of 300 DPI.
| Image | At 72 DPI (screen) | At 150 DPI (good draft) | At 300 DPI (photo print) |
|---|---|---|---|
| 1920 × 1080 | 26.67 × 15.00 in | 12.80 × 7.20 in | 6.40 × 3.60 in |
| 4000 × 3000 | 55.56 × 41.67 in | 26.67 × 20.00 in | 13.33 × 10.00 in |
| 6000 × 4000 | 83.33 × 55.56 in | 40.00 × 26.67 in | 20.00 × 13.33 in |
The diagonal follows the same rule, with Pythagoras first: the pixel diagonal of 1920 × 1080 is the square root of 1920 squared plus 1080 squared, which is 2,203 pixels, and dividing by the DPI gives the print diagonal, 7.34 inches at 300 DPI and 14.69 inches at 150 DPI. That diagonal is the number monitor and television sizes quote, which is why a 27-inch monitor is not 27 inches wide: it is 27 inches on the diagonal, and its width depends on its ratio. A 27-inch 16:9 monitor is about 23.5 inches wide and 13.2 inches tall, while a 27-inch 16:10 monitor is about 22.9 inches wide and 14.3 inches tall.
One misconception causes more print errors than any other: changing the DPI number stored in a file does not change the image. A 1920 × 1080 file marked 72 DPI and the same file marked 300 DPI contain the same pixels, and they print at the same size whenever the printer is told a size, because the printer divides pixels by the DPI it is given at print time. DPI only becomes a size when it is used as the divisor, which is exactly what the Advanced panel does. If a print shop asks for 300 DPI, what it is really asking for is enough pixels that the division lands on the size you want: an 8 × 10 inch print at 300 DPI needs 2,400 × 3,000 pixels, and no metadata value can supply pixels that are not there.
Resizing with the shape locked, and the rounding problem
Resizing with the shape locked means changing one side and letting the other follow by the same factor, and the calculator does exactly that: enter a new width and it fills in the matching height, or enter a percentage in Advanced options and it sets the new width for you. The factor is the whole method. Halving 1920 × 1080 gives 960 × 540, because both sides are multiplied by 0.5, and the ratio stays 16:9 exactly. Scaling 1920 × 1080 to 66.67% gives 1280 × 720, which is the calculator’s default resize, and the ratio stays 16:9 exactly because 1280 and 720 share the same divisor structure.
Rounding is where locked resizing meets reality. Pixels are whole, so a scale factor that lands between whole pixels forces a choice, and the choice changes the ratio by a hair. Scale 1366 × 768 by 70% and the exact answer is 956.2 × 537.6 pixels; the nearest whole pixels are 956 × 538, whose ratio is 1.7770 against the original 1.7786. The shift is about a tenth of a percent, invisible to the eye, but it means the resized image is not exactly the same shape, and repeated resizes accumulate the drift. The honest workflow is to resize once from the original, not repeatedly from resized copies, and to accept that whole-pixel rounding is a property of the medium, not an error in the tool.
| Original | Scale | Exact resize | Whole-pixel resize |
|---|---|---|---|
| 1920 × 1080 | 50% | 960 × 540 | 960 × 540, exact |
| 1920 × 1080 | 25% | 480 × 270 | 480 × 270, exact |
| 1366 × 768 | 70% | 956.2 × 537.6 | 956 × 538, ratio shifts by about 0.1% |
| 1366 × 768 | 50% | 683 × 384 | 683 × 384, exact, and the true ratio itself |
Two resizing mistakes account for most distorted images. The first is changing one side alone: setting a new width without letting the height follow stretches or squeezes the image, which is sometimes wanted for anamorphic video and almost never wanted for photographs. The second is cropping confused with resizing: cropping cuts pixels away and changes the ratio deliberately, while resizing keeps every pixel’s relative position and preserves the ratio as closely as whole pixels allow. If the brief wants a different ratio, crop; if it wants the same picture smaller or larger, resize with the shape locked, and use the percentage tool in Advanced options so the factor is explicit rather than guessed.
Diagonal, megapixels and what they do not tell you
The diagonal in pixels is the straight-line distance between opposite corners, worked out with Pythagoras: the square root of width squared plus height squared. For 1920 × 1080 that is 2,203 pixels, and for 1366 × 768 it is 1,567 pixels. The pixel diagonal is useful for comparing two images of the same shape, but it says nothing about physical size on its own: a phone screen and a cinema screen can share a ratio and even a pixel count while differing enormously in inches, because inches need a DPI or a physical measurement that pixels alone do not carry. The Advanced panel’s print diagonal supplies the missing step by dividing the pixel diagonal by the DPI.
Megapixels are simpler: width times height divided by one million. A 1920 × 1080 image is 2,073,600 pixels, or 2.07 megapixels; a 1366 × 768 image is 1,049,088 pixels, or 1.05 megapixels; a 6000 × 4000 photograph is 24 megapixels. The number counts pixels and nothing else, which is why it is a poor quality measure on its own. A 24-megapixel phone photograph and a 24-megapixel full-frame photograph contain the same count of pixels, but the larger sensor gathers more light per pixel, and the lens, processing and print size decide what the count is worth. Megapixels answer how large you can print before pixels show, not how good the picture is: at 300 DPI, 24 megapixels prints 20 × 13.33 inches, and beyond that size the pixels, not the subject, become visible.
Area follows the same count in a different form. Doubling both sides quadruples the pixel count, so a 4K frame at 3840 × 2160 contains 8,294,400 pixels, exactly four times the 2,073,600 of a 1920 × 1080 frame, and a file stored uncompressed grows by the same factor. That squaring is why resolution jumps feel disproportionate: the step from 1080p to 4K is a doubling of each side but a quadrupling of the work, in pixels, in storage, and in processing. The calculator’s pixel count, shown beside every ratio, is the place to see that factor before committing to it.
Video and social ratios: 16:9, 9:16, 1:1, and safe areas
Each platform has a native ratio, and a video made in the wrong ratio is cropped, letterboxed, or pillarboxed. Choose the ratio for the placement, not for the camera.
Landscape video is 16:9, the ratio of 1920 by 1080 and 3840 by 2160, and it is the native ratio for YouTube watch pages, television, and desktop embeds. Vertical video is 9:16, the same ratio turned on its side, 1080 by 1920, and it is the native ratio for Shorts, Reels, and TikTok, where the phone is held upright and the video fills the screen. Square video is 1:1, 1080 by 1080, and it is the feed ratio that reads equally on desktop and mobile without rotation, at the cost of unused screen area on both. A video shot in one ratio and placed in another is handled by cropping, which discards the edges, by letterboxing or pillarboxing, which adds bars, or by blurring the background behind a centred frame, and each handling loses something: cropping loses content, bars lose impact, and the blurred background looks untidy. Shoot and edit in the placement ratio wherever the placement is known in advance, and export separate versions where two placements matter, rather than forcing one export to serve both.
Safe areas are the second consideration, after the ratio itself. Text and logos must sit inside the area that survives every handling: clear of the top and bottom bars where platform interfaces overlay, clear of the edges where cropping bites, and centred where a square crop of a landscape video is possible. The calculator ratio and resize tools give the pixel dimensions for any ratio at any width, and the rounding note on this page explains why a resized image sometimes changes ratio by a pixel: dimensions must be whole pixels, and locking the ratio while rounding each side independently can shift the ratio by one pixel in a thousand, which is invisible in practice and worth knowing about when a platform demands exact dimensions. The companion guide works the golden ratio separately, and its sizes are exact arithmetic from phi, not platform conventions; the two guides answer different questions, and the ratio entered decides which one applies.
Aspect ratio questions, answered
How do I calculate an aspect ratio?
Divide the width and the height by their greatest common divisor — the largest number that divides both exactly. For 1,920 × 1,080 the GCD is 120, giving 16:9. If the two sides share only a small GCD, the honest ratio can look unusual: 1,366 × 768 gives 683:384. This page does the division for you and always uses whole-number GCD arithmetic, never a rounded decimal, so the ratio it shows is exact.
What is the aspect ratio of 1920×1080?
16:9 — the widescreen standard for TVs, monitors and online video. As a decimal it is 1.7778:1, the frame holds 2,073,600 pixels (2.07 megapixels), and its diagonal measures 2,203 pixels. The standard sizes on the same shape are 1280×720 (720p), 2560×1440 (1440p), 3840×2160 (4K) and 7680×4320 (8K).
How do I resize an image without distorting it?
Scale both sides by the same factor — or, what amounts to the same thing, set one side and solve the other from the ratio: new height = new width × (height ÷ width). Sending 1,920 × 1,080 to a width of 1,280 gives a height of exactly 720. If the exact answer is fractional, like 666.67 px on a 3:2 frame at 1,000 px wide, round to the nearest whole pixel (667) — the fraction of a pixel is invisible, and stretching is what actually distorts.
What are the most common aspect ratios?
16:9 for video and modern screens; 4:3 for older monitors and many photos (4000×3000 is exactly 4:3); 3:2 for 35 mm film and DSLR sensors; 1:1 square for social posts; 21:9 for ultrawide monitors — which simplifies to 7:3, and many panels sold as 21:9, like a 3440×1440, are really 43:18; and 9:16 for portrait phone video. The chips at the top of this page load an example of each.
Is 1366×768 really 16:9?
Nearly, but not exactly. 1,366 and 768 share a GCD of just 2, so the panel’s true ratio is 683:384 = 1.7786:1, where true 16:9 is 1.7778:1 — a difference of about 0.05%. Panels are manufactured to pixel counts, not ratio names, and the name is rounded for the box. It only matters if you resize with 16:9 maths and land a fraction of a pixel out; this page always works from the actual pixels.
What does the diagonal in pixels mean?
It is the straight-line distance from one corner of the frame to the opposite one, measured in pixels: the square root of width squared plus height squared. For 1,920 × 1,080 that is 2,202.9 px, shown rounded as 2,203. Screens are sold by this diagonal in inches, which is why two same-sized monitors can hold very different pixel counts — the pixel diagonal on this page lets you compare the actual frames behind the inch labels.
How big will my image print at 300 DPI?
Divide each side in pixels by 300. A 1920 × 1080 image prints 6.40 × 3.60 inches at 300 DPI, with a diagonal of 7.34 inches, and a 6000 × 4000 photograph prints 20.00 × 13.33 inches. The Advanced options panel works out the print size and diagonal live for your image at any DPI you enter.
Why does resizing sometimes change the ratio slightly?
Because pixels are whole. Scaling 1366 × 768 by 70% gives exactly 956.2 × 537.6 pixels, and the nearest whole pixels, 956 × 538, have a ratio of 1.7770 against the original 1.7786. The shift is about a tenth of a percent and invisible to the eye, but it is real, so resize once from the original rather than repeatedly from resized copies.
What is the exact ratio of an ultrawide monitor?
It depends on the pixel size, because 21:9 is a marketing family, not an exact ratio. A 2560 × 1080 monitor is exactly 64:27 (2.370), and a 3440 × 1440 monitor is exactly 43:18 (2.389), while 21:9 itself is 2.333. If a brief says 21:9, ask which pixel size it means.
Do more megapixels mean a better picture?
No, megapixels count pixels only: width times height divided by one million. A 1920 × 1080 image is 2.07 megapixels, and a 6000 × 4000 photograph is 24 megapixels, which prints 20 × 13.33 inches at 300 DPI. Sensor size, lens and processing decide what those pixels are worth, and megapixels alone answer only how large you can print before pixels show.
What is the golden ratio, and how is it calculated?
The golden ratio, phi, is (1 + sqrt(5)) / 2, about 1.618034, defined by dividing a line so the whole relates to the longer part as the longer part relates to the shorter part. A rectangle is golden when its longer side divided by its shorter side equals phi. The companion guide derives the formula, works its sizes, and separates its real uses from its myths.
Is 16:10 the golden ratio?
No, but it is the closest common screen ratio: 16:10 is 1.6, against phi at 1.618034, a difference of about 1%. It is sometimes described as near-golden, but it is not golden, and the difference exceeds manufacturing tolerance. A golden screen at 1920 pixels wide would be about 1187 pixels high, against 1200 for 16:10.
What aspect ratio should I use for YouTube Shorts?
9:16 vertical, 1080 by 1920 pixels, which fills a phone held upright. Landscape 16:9 video placed in Shorts is cropped or letterboxed, losing content or impact. Shoot and edit vertical where Shorts is the placement, keep text inside the safe area clear of platform overlays, and export a separate 16:9 version for the watch page where both placements matter.
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→Whole pixels, exact ratios.
Every ratio on this page is simplified with exact greatest-common-divisor arithmetic, and every resize is rounded to the nearest whole pixel, with the unrounded figure always shown. Pixel counts describe the frame, not the file: compression, colour depth and format decide how many bytes an image takes, and a screen’s physical size in inches is a separate measurement from its resolution. Check the export settings in your editor before a print or broadcast deadline — a one-pixel rounding is invisible, but the wrong ratio is not.