Ideal Weight by Height, Sex and Age: Charts in kg and lb

They get used interchangeably and they are not the same thing.

• Ideal body weight is a single number produced by a formula from your height and sex. The best-known, the Devine formula, was published in 1974 as a way to size a drug dose - specifically gentamicin - for patients whose weight would otherwise skew the calculation. It was never derived from health outcomes, never validated against mortality or disease, and its author offered it without supporting data. Robinson (1983) and a handful of others adjusted the constants; they share the same ancestry.
• The healthy weight range is the standard BMI band of 18.5 to 24.9 converted back into kilograms for your height. It is what WHO, the CDC, the NHS and every major guideline publish, it is identical for women and men, and at 170 cm it spans about 19 kg.

So the formulas give you precision that the evidence does not support, and the guidelines give you a range that feels uselessly wide. Both are on the charts below, because reading them together is more honest than reading either alone: if your formula figure and the BMI band disagree, the band is the one with health outcomes behind it.

One structural quirk worth knowing: these formulas are anchored at 5 ft (152 cm) and add a fixed amount per inch above it. Below about 150 cm they return numbers that are too low to be sensible, and at the extremes of height they drift away from the BMI range in both directions.

Devine and Robinson figures for women, with the healthy BMI range for the same height beside them. Heights in feet and inches are rounded to the nearest inch.

Notice how the two formulas cross over at around 167 cm: Robinson is the higher number for shorter women and the lower one for taller women, because it adds less weight per inch. Notice also that both sit near the lower half of the healthy range at most heights - a woman of 170 cm at 65 kg is nowhere near her "ideal weight" of 61 kg and is comfortably, unremarkably healthy.

The same three columns for men. The formulas add 4.5 kg (Devine) or 3 kg (Robinson) at the 5 ft anchor point compared with the women's version, then rise at the same or a slightly steeper rate.

Both formulas fall inside the healthy BMI range at every height here, usually a little below its midpoint. That is the useful way to read them: not as a target, but as a rough marker of where the middle of your range sits.

To convert any of these to pounds, multiply by 2.2 - a Devine figure of 65.9 kg for a 170 cm man is about 145 lb, and his healthy range of 53.5 to 72 kg is about 118 to 159 lb.

This is the most searched version of the question and the honest answer is uncomfortable: no major guideline publishes an ideal weight or a healthy BMI range that varies by age for adults. The 18.5 to 24.9 band is defined for everyone from 18 upwards, and the Devine and Robinson formulas contain no age term at all. Any chart offering you a different ideal weight for 25, 45 and 65 is inventing the difference.

Two real things do change underneath that stable number:

• Composition drifts. From the 30s onward, muscle is gradually lost and fat gained at an unchanged weight, and measured height slowly decreases from around 40 - which nudges your BMI up without a gram of weight gained. The same 70 kg is a different body at 30 and at 70.
• The evidence softens at the top of the range after about 65. A meta-analysis of BMI and mortality in older adults found the lowest risk at a BMI somewhat above the standard band, in the region of 23 to 30 rather than 18.5 to 24.9, and being underweight in later life carries clearer risk than being mildly overweight. Unintentional weight loss after 65 is a warning sign; a few stable extra kilograms usually is not.

That is not permission to aim higher, and it is not a reason to diet harder either. It means the bottom of the range is the wrong target in later life, and that weight changes in later life are worth watching for their direction rather than their distance from a formula - which means weighing regularly enough to see a trend.

Height and sex explain a lot of the variation between people, but not all of it. The old ideal weight tables tried to handle the rest with frame size - small, medium, large, judged from elbow breadth or wrist circumference - and added or subtracted around 10 percent at each end. It is a crude proxy for skeletal build, still roughly the right instinct, and not something you need a chart for: a broad-shouldered, thick-wristed person of 175 cm genuinely carries more healthy weight than a narrow-framed one.

Two measurements say more than frame size ever did:

• Waist-to-height ratio. Keep your waist under half your height. It costs thirty seconds, it needs no formula for sex or age, and it captures abdominal fat, which is the part most strongly linked to risk - see the waist-to-height ratio guide.
• Body fat percentage. Two people of identical height and weight can differ enormously in composition. If you train, the scale will call you heavier than your "ideal" while your body fat percentage says otherwise - and the percentage is right.

This is also why a muscular athlete can be flagged overweight by BMI and by these formulas at once. Neither can tell muscle from fat; they only know height.

Treat the formula figure as one marker inside a range rather than a destination:

1. Read your row as a band, not a number. The BMI column is your actual target zone; the Devine and Robinson figures show roughly where its lower-middle sits.
2. Start from where you have been. A weight you held comfortably for a year, without restricting, is a better goal than anything a chart hands you.
3. Set a rate, not just a target. If you are heading down, 0.5 to 1 kg (1 to 2 lb) a week is the sensible band - see how much weight you can safely lose per week. Losing 5 percent already moves blood pressure and blood sugar measurably.
4. Check the waist as well as the scale. Two numbers, thirty seconds, far more information than one.
5. Weigh under the same conditions. Same time, same clothing, same scale, and judge by the month - daily readings swing by a kilogram or more on water alone.

That last part is where a log earns its keep. The free Weight Journal app charts weight and BMI with a trend line through the daily noise, tracks the distance to a goal you set, keeps body fat alongside weight so composition is visible, and syncs with Apple Health and across devices via iCloud with no account or email. Export to PDF, XLSX, CSV or JSON if you want to take a year of readings to an appointment.

The ideal weight formulas were a dosing tool that escaped the pharmacy. Use them as a landmark, and let the range, the waist and the trend do the actual work.