Time Duration Calculator — Exactly How Long Between Two Moments
Pick a start and an end — two dates and times, or just two times on the same day. Get the exact duration as weeks, days, hours, minutes, and seconds — plus totals in hours, minutes, seconds, days, and weeks.
Your two moments
🔒 All calculations happen in your browser — no data leaves your device.
The duration
Your duration as a timeline
The bar stretches from start to finish, split into days, hours, minutes, and seconds.
- The duration is end minus start, split into days, hours, minutes and seconds — and the same span is also given as one number in total hours or total minutes.
- A 9:00 AM to 5:30 PM span is 8.5 hours, or 510 minutes: the breakdown rows are the “clock” reading, the totals are the same span in one unit.
- There is no upper limit — multi-day, multi-month and multi-year spans work the same way; the day count just keeps growing.
Keep exploring
Three companion tools for dates and times.
How it works
Three steps from two moments to one exact number.
Pick the start
Choose the start date and time — the moment you want to measure from.
Pick the end
Choose the end date and time. If it falls before the start, you will get a friendly nudge — and the Swap button exchanges the two in one click.
Read every unit
The breakdown and every total — hours, minutes, seconds, days and weeks — appear when you press Calculate.
The math behind your duration
Duration is one subtraction: end − start, in milliseconds. Dividing that single number by 86,400,000 (ms per day), 3,600,000 (ms per hour), and 60,000 (ms per minute) gives every unit. The same number also gives the totals in seconds (÷ 1,000), days (÷ 86,400,000) and weeks (÷ 604,800,000) — and for spans of a week or more, the breakdown peels whole weeks off the day count first, so the rows always add back up to exactly the same total.
Worked examples:
| Start → End | Calculation | Result |
|---|---|---|
| Jan 5, 9:00 AM → 5:30 PM | 8.5 × 60 | 0d 8h 30m · 8.5 hours · 510 minutes |
| Jan 1, 8:00 AM → Jan 3, 10:30 AM | 50.5 hours | 2d 2h 30m · 50.5 hours · 3,030 minutes |
| 12:00:00 PM → 12:01:45 PM | 105 seconds | 0d 0h 1m 45s · 1.75 minutes |
| Feb 28, 2024 → Mar 1, 2024 (leap year) | includes Feb 29 | 2d 0h 0m · 48 hours |
| End before start | negative span | Friendly error, no result |
Go deeper
The details that separate a rough guess from a trustworthy number.
The breakdown (days, hours, minutes, seconds) is the “clock reading” of the span: each unit only holds its remainder after the bigger units take their share. A span of 50.5 hours reads as 2 days, 2 hours, 30 minutes — not 50 hours.
The totals express the whole span in one unit: 50.5 total hours, 3,030 total minutes, 181,800 total seconds — or about 2.1 total days. For spans of a week or longer the breakdown first peels off whole weeks, so a 16-day span reads as 2 weeks and 2 days while the rows still sum to exactly the same total. Use the breakdown when you want something readable (“2 days and 2 hours”); use the totals when you need one number for math, like multiplying by an hourly rate.
Not at all for durations — the calculator counts actual elapsed milliseconds, so February 29 and 31-day months are handled exactly. A span from Feb 28 to Mar 1 in a leap year is 2 days (48 hours), and 1 day in a common year. The day count simply keeps growing past a month or a year with no special rules needed.
Frequently asked questions
Quick answers about this time duration calculator.
How do you calculate the duration between two dates and times?
Subtract the start from the end to get the elapsed time, then split it into days, hours, minutes, and seconds. Enter both moments above and this calculator does it instantly.
How do I find the number of hours between two times?
Enter the start and end above and read the “Total hours” row — a 9:00 AM to 5:30 PM span is 8.5 hours. For two times on the same day, the breakdown and the total agree exactly.
How do you convert a duration into total minutes?
Multiply total hours by 60, or read the “Total minutes” row above — an 8.5-hour span is 510 minutes. Press Calculate after changing a time and the row updates with the new span.
What happens if the end time is before the start time?
You get a friendly error message instead of a negative duration. Click the Swap button to exchange the two moments (or fix the one you mistyped) and the result appears. In Time only mode there is no error — an earlier end time is counted as the next day.
Can this calculator handle durations longer than a day?
Yes — the day count keeps growing with no upper limit, so multi-day, multi-month, and multi-year spans all work. Spans of a week or more also get a weeks row in the breakdown: Jan 1, 8:00 AM to Jan 17, 11:04 AM reads as 2 weeks, 2 days, 3 hours, 4 minutes.
Is this time duration calculator free to use?
Yes — completely free, with no sign-up. Both dates are processed in your browser and never leave your device.
Does this calculator count business days?
No. It counts every calendar day, weekends included. Forty-five business days after Monday, October 26, 2026 is Monday, December 28, 2026 — 63 calendar days later, because 45 business days are exactly 9 working weeks. For legal deadlines, count against the applicable holiday calendar as well.
Why is there no months or years row in the breakdown?
Because months and years are not fixed lengths: a month is 28, 29, 30, or 31 days, so a span in months cannot be converted without its start and end dates. The breakdown stops at weeks so its rows always add back up to the same total.
Days ago, days from today, and business days — what this tool does and does not do
This calculator measures between two moments you already know. Finding an unknown date is a different job — here is how it works.
A duration needs two known moments. A question like “180 days ago” gives you one known moment (today) and a length, and asks for the other moment — so it is a date question, not a duration question, and the calculator cannot answer it directly. The method is counting back across real month lengths: 180 days before October 27, 2026 is April 30, 2026, because 27 days back reaches September 30, then 30 to August 31, 31 to July 31, 31 to June 30, 30 to May 31, and 31 to April 30 — and 27 + 30 + 31 + 31 + 30 + 31 = 180. Once both dates are known, enter them above and the calculator gives the exact span in every unit.
Business days need a separate count, because the calculator counts every calendar day, weekends included. Forty-five business days after Monday, October 26, 2026 is Monday, December 28, 2026 — 63 calendar days later, because 45 business days are exactly 9 working weeks. Count Monday-to-Friday days after the start date, skipping weekends; public holidays are not excluded by a weekday count, so for legal deadlines count against the applicable holiday calendar as well. And the breakdown stops at weeks for a reason: months and years are not fixed lengths (28 to 31 days), so a span in months cannot be converted without its start and end dates.
Related guides
Deeper reading on elapsed time, from this page’s own guides.
Related calculators
More ways to measure time and dates.
Disclaimer
This calculator provides time-span math for information only. Results use the exact elapsed time between the two moments you enter, in your browser’s local time zone. Daylight-saving transitions can make a local “24 hours” read as 23 or 25 — for legal deadlines, travel itineraries, or shift differentials, verify against an authoritative schedule.