No published ideal-weight formula takes an age input, and the BMI healthy range is the same at every adult age, so an age-adjusted ideal weight is an invention. What genuinely shifts across life is composition: muscle falls, fat moves centrally, height shortens, and strength becomes the measure that matters. This guide follows those shifts decade by decade, with the fixed arithmetic held constant throughout.

The formulas do not know your age, and that is the point

Ask what your ideal weight is at 50, at 60, or at 70, and the honest answer begins with a surprise: the four classic ideal-weight formulas, Devine, Robinson, Miller, and Hamwi, give exactly the same answer at every age. No published formula in the set takes an age input. A man of 5 feet 9 inches receives Devine 70.7 kg, Robinson 69.1 kg, Miller 68.9 kg, and Hamwi 72.3 kg whether he is 25 or 75, and a woman of the same height receives 66.2, 64.3, 65.3, and 65.3 kg at every age too. The BMI healthy weight range is likewise age-free for adults: 56.8 to 76.5 kg at that height, from 18.5 to 24.9 times height squared, at every adult age. If the arithmetic never changes, what changes with age? Everything the arithmetic cannot see: muscle, bone, fat distribution, strength, and the meaning of a stable weight. This guide follows those changes decade by decade, using the same reference numbers throughout, so that the shifting part of the story is never confused with the fixed part.

The fixed part deserves stating once, clearly, because it anchors the whole guide. Height determines the formula cluster and the BMI range, sex shifts the cluster by a few kilograms, and age shifts neither. Anyone selling an age-adjusted ideal weight, a chart of ideal weights by age with a different target for each decade, is selling an invention, because no published classification supports one. Population averages by age exist, and they rise with age, but averages describe what is typical in populations where weight gain with age is common, not what is healthy for an individual. The companion guide comparing the four formulas gives the cluster in full at three heights. This guide keeps the 5 feet 9 inch example running throughout, so the decade sections can be compared like with like, and the reader can substitute their own height’s cluster from the calculator without relearning the argument.

Your 20s and 30s: building the reference

The 20s and 30s are the reference decades, the period when height is at its adult maximum, muscle mass is near its peak, bone density is being consolidated, and the formula cluster and the BMI range describe the body most straightforwardly. Weight gained in these decades is most often fat gained gradually, a kilogram or two a year that the BMI band hides until it crosses 25, and the most useful habit of the period is the trend: the same scale, the same conditions, noted every few months, so that a slow drift is visible while it is still small. Strength training in these decades is not cosmetic preparation. It is the deposit that the later decades withdraw from, because muscle built and maintained early is the reserve that protects function later, and the formulas, which ignore muscle entirely, will credit none of it.

The healthy range in these decades should be read as a wide neighbourhood. At 5 feet 9 inches, anywhere from 56.8 to 76.5 kg sits inside the BMI band, and no point inside it is healthier than any other on BMI evidence alone. Waist circumference adds the information the band lacks: below 102 cm for men and below 88 cm for women, measured at the navel, marks the general threshold, with a waist-to-height ratio below 0.5 as the height-adjusted equivalent. Body-fat percentage, where it is measured, adds the composition the band lacks. A 30-year-old at the top of the band who trains, with a small waist and a low body-fat percentage, and a 30-year-old at the same weight who does not, share a BMI and share little else. The decade’s lesson is to establish the measures, waist and trend alongside weight, that will make the later decades readable.

Your 40s and 50s: distribution shifts, muscle begins to go

Through the 40s and 50s, two slow changes alter the meaning of a stable weight. First, muscle mass begins to decline, from around age 30 onward, at a rate that accelerates without resistance training. Second, fat distribution shifts toward the abdomen, in men progressively and in women more sharply around the menopause, as oestrogen falls and the pattern of storage changes. A weight that has not moved in ten years can therefore describe a body that has lost muscle and gained central fat in equal measure, with the same BMI, the same formula cluster, and a worse composition. The scale, faithfully reporting no change, hides the change that matters. Waist circumference catches it. Strength catches it. The percentage, where measured, catches it. Weight alone does not.

For women, the menopause transition deserves a specific word, because it is the largest single compositional event of these decades and the formulas are silent about it. The shift in fat distribution toward the abdomen is real, the tendency to gain central fat increases, and bone density begins the decline that accelerates after the menopause. None of this changes the ideal-weight arithmetic, and none of it justifies a new target weight. It justifies attention to waist, to resistance training, and to bone health, through clinical guidance where appropriate, and it justifies reading a stable weight with more suspicion than in the 30s. For men, the parallel event is slower and less marked: a gradual fall in testosterone, a gradual loss of muscle, and the same central shift, spread over more years. The response in both cases is the same set of measures, not a new number.

Your 60s: height, muscle, and the meaning of stability

In the 60s, height itself begins to change the arithmetic. Spinal compression, disc changes, and posture changes shorten measured stature, often by a centimetre or two across a decade, and a BMI computed from a shortened height overstates the BMI that the younger height would have given. A man who was 5 feet 9 inches at 40 and measures 5 feet 8 inches at 65 has lost an inch of height, not gained a point of BMI, and the fairer reading uses a carefully measured current height with good posture, or the younger-adult height for trend purposes, with the change noted. The formula cluster, which also uses height, shifts with the same change, and the same caution applies: compare like with like, height with height, and do not let shrinkage masquerade as weight gain.

Muscle loss accelerates in the 60s, and with it the importance of strength as a companion measure. Grip strength, chair-rise ability, and walking speed are simple functional checks that say more about the decade’s health than any weight figure, and they are worth more attention than a decimal point of BMI. Weight stability in the 60s is itself a health signal: a stable weight, stable waist, and maintained strength is a good picture at any point in the BMI band, while unintentional weight loss, of any size, deserves clinical attention regardless of where BMI sits, because it can signal illness, appetite loss, or muscle loss that the band cannot see. The chart has not stopped applying. It has become one input among several, and the others now carry equal weight.

Your 70s and beyond: when the band needs the most context

After 70, the BMI band needs the most context of any decade, for reasons that pull in opposite directions and must both be held in mind. On one side, low weight and weight loss carry greater risk in later life: frailty, falls, bone fracture, and the loss of reserve against illness all rise as weight and muscle fall, and a BMI near the bottom of the band, or below it, deserves attention even when it was unremarkable at 40. On the other side, high BMI in later life is less clearly adverse than in midlife in population data, with some studies finding the lowest mortality in older adults sitting in the high 20s, a finding confounded by illness-related weight loss in the lower bands and one that has not changed the official classification. Neither observation justifies adopting a higher personal target. Together, they justify treating the band as a screen and the clinical picture as the decision, with weight trend, appetite, strength, mobility, and bone health as the deciding inputs.

The practical reading for the 70s and beyond is therefore conservative in the best sense: protect muscle, protect bone, protect appetite, and treat the weight trend as a vital sign. Resistance training adapted to ability, adequate protein within clinical guidance, vitamin D and calcium as advised, and attention to falls and fracture risk matter more than any formula answer, and none of them appears in the arithmetic. The formula cluster at 5 feet 9 inches still reads 68.7 to 72.3 kg for a man, and the BMI range still reads 56.8 to 76.5 kg, and both remain true as reference numbers. What has changed is the weight given to them relative to the rest of the picture. In the 20s, the band and the cluster were most of the story. In the 70s, they are the frame, and the picture inside the frame is strength, mobility, appetite, and trend.

Frame, composition, and the 10% convention

Frame size is the one adjustment the formula tradition does allow, and it is worth understanding because it is often misused. The convention on this site allows plus or minus 10% around the formula answers for large and small frames, classified roughly by wrist circumference relative to height. A large-framed person at the top of the cluster plus 10% and a small-framed person at the bottom minus 10% are both inside the convention, and the spread it creates, roughly 14 kg at the 5 feet 9 inch cluster, is a fair picture of how much build alone moves healthy weight. The convention is rough, not precise: wrist circumference is a proxy, the 10% is a round-number allowance, and the classification boundaries are conventions rather than measurements. Use it as a reminder that the cluster is a neighbourhood, not as a corrected prescription.

Body composition is the deeper adjustment, and it grows more important with every decade. Two people of the same height, sex, age, and weight can differ by 10 kg or more in fat mass, with the difference made up in muscle, and the formulas will give them identical answers. Body-fat percentage, measured consistently by one method, separates those two people, and lean mass in kilograms separates them better still, because it shows whether a changing weight is fat or muscle changing. The companion guide on body-fat charts by age and sex gives the classification bands for both sexes, and the guide on the Navy method explains how to measure repeatably at home. As the decades pass, the composition measures do not replace the weight measures. They complete them, and the completion matters more each decade.

Using age well: trend, waist, strength, and the range

The usable summary of this guide fits in four habits, valid at every age and increasingly valuable with each decade. First, weigh consistently, same scale, same conditions, and record the trend over months and years rather than the daily figure. Second, measure the waist at the same intervals, because the waist catches the central-fat shift that weight misses. Third, maintain and notice strength, through resistance training where possible and through simple functional checks, because strength is the functional reserve that weight cannot report. Fourth, read the BMI range and the formula cluster as the frame, not the picture, and bring the picture, trend, waist, strength, and composition, to clinical conversations when it changes unexpectedly. Those four habits use the numbers this site provides without asking them to do a job they cannot do.

What not to do is equally clear. Do not chase a different target weight for each decade, because no published classification supports one and the chase itself does harm by turning a stable, healthy weight into a perceived failure. Do not treat a population average for your age as a target, because averages describe populations where weight gain is common, not individuals where health is the aim. Do not adjust the formula answers for age by inventing a correction, and do not use a calculator result, from this site or any other, as a medical judgement. The arithmetic is fixed across the decades. The body is not. The wisdom is in knowing which part of the story each belongs to, and in letting the fixed numbers frame a changing picture that is read with waist, strength, trend, and clinical context together.

Frequently asked questions

What is a healthy weight for my age?

The BMI healthy range for your height applies at every adult age, and the four ideal-weight formulas give the same answers at every age too, because no published formula takes an age input. What changes with age is composition, muscle, and fat distribution, so read the range with waist, strength, and trend alongside.

Does ideal weight change as you get older?

The formula answers do not change, because the formulas use height and sex only. The meaning of a given weight changes: muscle tends to fall, fat shifts centrally, and height can shorten. Those changes affect interpretation and the measures that should accompany weight, not the arithmetic.

What is the ideal weight for a 60-year-old man?

There is no age-specific ideal weight. For a man of 5 feet 9 inches, the four formulas give 68.7 to 72.3 kg at every age, inside a BMI healthy range of 56.8 to 76.5 kg. In the 60s, waist, strength, and weight trend matter as much as the weight itself.

Is it normal to gain weight with age?

Gradual weight gain with age is common in population data, driven by less activity, muscle loss, and hormonal change, but common is not the same as healthy or inevitable. A slow upward trend is worth noticing early, while it is small, through consistent weighing and waist measurement.

Should older adults aim for a higher BMI?

No personal target should be adopted from population studies. Some studies find lower mortality at slightly higher BMIs in older adults, but the finding is confounded by illness-related weight loss and has not changed the official bands. Discuss any weight goal with a clinician who knows your health history.

How does menopause affect ideal weight?

Menopause does not change the ideal-weight arithmetic, which ignores age and hormones. It changes fat distribution toward the abdomen, accelerates bone loss, and tends to reduce muscle mass. Waist measurement, resistance training, and bone health deserve more attention through the transition, with clinical guidance where appropriate.