How Much Should I Weigh? Setting a Real Target
Ask how much you should weigh and the internet hands back a single number from a formula written in 1974 for calculating drug doses. Ask what the healthy range is for your height and you get a band around 19 kg wide.
The band is the honest answer. Here is how to pick a point inside it that means something.
Why the formulas disagree
At 178 cm, Devine says 73.7 kg, Robinson says 72.6 kg, Miller says 69.3 kg and Hamwi says 75.7 kg. Six and a half kilos separate the highest from the lowest. All four get quoted as ideal.
Not one of them came from health outcomes. Devine wrote his in 1974 for gentamicin dosing, and Hamwi wrote his in 1964 for diabetic diet planning. They spread into fitness culture because they were simple and already printed on the charts.
The ideal weight calculator runs all four so you can see the whole spread instead of one figure presented as fact, and the four formulas and why they disagree covers where each one came from.
Work from your lean mass instead
Your lean mass is everything in you that is other than fat, and it holds roughly steady unless you deliberately train. Treat it as fixed, choose the body fat percentage you want, and your target weight falls straight out of the division.
Take a man at 92 kg. He measures his body fat at 26%, which puts 23.9 kg of fat on 68.1 kg of lean mass. He wants 15%.
At 15%, lean mass makes up 85% of total weight, so his target is 68.1 divided by 0.85, which is 80.1 kg. That figure came out of his own body and not out of a table, and it tells him exactly what the job is: lose 11.9 kg, all of it fat.
Now do it with your own numbers. Run tape measurements through the body fat calculator, multiply your weight by the percentage to get fat mass, subtract that to get lean mass, then divide your lean mass by one minus your target percentage.
Picking a target percentage
Use the American Council on Exercise bands. For men, 14 to 17% is the fitness range and 18 to 24% is average. For women, 21 to 24% is fitness and 25 to 31% is average.
Most men who want to look fit and still eat normally are after 13 to 16%, and most women are after 20 to 25%. Going lower is possible, and it gets progressively more expensive in attention. What 10% body fat costs spells out what that means day to day.
Sense-check it against the chart
Once you have a number, see where it sits in the healthy BMI range for your height. The man above lands at 80.1 kg. At 183 cm the healthy range runs 62 to 84 kg, so he is inside it and near the top, which is exactly where you would expect someone carrying 68 kg of lean mass to land.
If your composition target falls well outside the BMI range in either direction, look again. Well above usually means a lot of muscle, which is fine. Well below usually means you picked a target percentage too low for your frame.
What BMI measures covers where that range comes from and when to overrule it.
Then stop weighing the goal and start weighing the trend
Your daily weight swings by one to two kilos on food volume, sodium, glycogen and hormones. A target of 80.1 kg means nothing on any single morning. Weigh yourself in the same conditions most days, take a weekly average, and watch that line instead.
Why scale weight fluctuates covers what is normal, which is more than most people expect.
One case where the target should move
If you are new to serious lifting, your lean mass will climb while your fat falls, and your goal weight climbs with it. Recalculate every couple of months instead of chasing a figure you set in January. Body recomposition covers who this applies to.
Scope and correction note, 2 November 2026: the ranges quoted here come from the American Council on Exercise and from published research, and they describe averages, not any individual. Nothing on this page is medical advice. If a figure here is wrong, tell us and we will correct it and date the correction. See the editorial policy and medical disclaimer.