FitDexIdeal weight calculator
The honest answer to "what's my ideal weight?" isn't a number, it's a range. Two people of the same height genuinely differ in frame, muscle mass and fat distribution; handing over one figure would pretend that difference away. The calculation below gives you your own range and shows where you sit inside it.
Your healthy weight range
- Body mass index24.2 kg/m²
- Body fat percentage30.6%
This number comes from the very same formula the FitDex app uses. Install the app and you won't be handed a different target.
How is it calculated?
The range is worked backwards from the healthy band of body mass index: lower bound 18.5 × height(m)², upper bound 24.9 × height(m)². At 170 cm that's 53.5 to 72.0 kilos; at 180 cm it rises to 59.9 to 80.7.
We chose this over the old "ideal weight" equations. Devine (1974), Robinson (1983), Miller (1983) and Hamwi (1964) are all still in circulation and all disagree: for a woman of 170 cm, Devine says 61.6 kilos, Hamwi 57.9, Miller 58.6. On top of that, those equations were derived to calculate drug doses, not to set health targets — presenting them as a healthy weight range was a later borrowing.
The range is 6 to 8 kilos wide. That width is deliberate. Someone with high muscle mass can be healthy at the top end while someone with a light frame is healthy at the bottom, and the BMI and body fat estimate shown next to the range are there to help you tell which end is yours.
The calculation takes age and sex in addition to height and weight — but not for the range itself, for the body fat estimate beside it. The healthy weight range depends only on height; body fat, through the Deurenberg equation, also depends on age and sex.
How to read your result
If you're inside the range, there's nothing to do. Moving to the bottom end doesn't mean being healthier; when staying there takes constant restriction the odds of rebounding go up, which is why wherever in the range you can live without fighting yourself is the right place for you.
If you're above it, read the distance as a direction, not a target. You don't have to close all of it: losing 5–10% of your current weight produces measurable improvement in blood pressure, blood sugar and blood lipids, and that usually happens long before you reach the range. Going from 90 kilos to 82 is a far more meaningful win than failing to reach 72.
If you're below the range, look again. Being underweight carries its own risks — bone density, immune function and hormonal balance all take the hit. Here the goal isn't to lose but to add quality calories and build muscle with resistance training.
The direction matters more than the number. Going from 68 to 76 in a year at the same height is a different picture than having been 76 for two years, and the only way to tell those two apart is weighing once a week at the same time under the same conditions and reading the curve rather than any single figure.
Frequently asked questions
Why don't you give one single ideal weight number?
Because there isn't one — there are only sites that choose to give one anyway. The four classic equations still in circulation disagree by 4 to 8 kilos for the same height; whichever you pick moves where "ideal" lands. Publishing one number makes a page feel more satisfying but manufactures false precision: someone perfectly healthy inside the range reads themselves as two kilos "over" and starts restricting for nothing.
I'm muscular and above the range. Is that a problem?
Probably not. This range is derived from BMI, so it can't tell muscle from fat; someone who lifts regularly can sit 4–5 kilos above it with low body fat. The practical way to tell: measure your waist. If it's under 88 cm for women or 102 cm for men and your energy is fine, being above the range isn't in itself a diagnosis. The body fat estimate we show alongside is there to help you make the same distinction.
How long will it take to reach my ideal weight?
A sustainable pace is 0.5 to 1% of current weight per week — at 90 kilos, that's 450 to 900 grams. On that basis, 8 kilos is a 9 to 18 week job. But the real curve isn't a straight line: as weight drops, so does basal metabolism, so the same deficit yields less each week. That's why sites that assume a flat 7,700 calories per kilo always promise faster timelines than reality delivers. The FitDex weight timeline recalculates this every week.
Related tools
- BMI calculatorEnter your height and weight to see your body mass index, which category it falls in and the healthy weight range for your height. A body fat estimate comes with it — it says what BMI alone cannot.
- Calorie calculatorEnter your height, weight, age and activity level to see your daily calorie needs, basal metabolic rate and macro split in seconds. The same formula as the FitDex app.
- Body fat calculatorEstimate your body fat percentage and lean mass from height, weight, age and sex. We don't ask for a tape measure — and we explain why, along with the margin of error.
- Weight loss timelineSee how many weeks it takes to reach your goal weight — under both a fixed calorie intake and one you re-adjust each week. The two dates aren't the same, and we explain why.
This tool is for information only and is not a substitute for medical diagnosis or treatment. Talk to a healthcare professional before making a lasting change to how you eat.