Enter your height and weight to get your BMI, healthy weight range, BMR and the calories you should eat each day — all at once

How to use it

1. In the left card choose your sex and enter age, height in centimeters and weight in kilograms. The form opens with 30 years, 170 cm and 65 kg as an example; the results on the right change as soon as you edit a number.
2. Pick one of the five activity levels. A line under the buttons describes each one ("Desk job, little or no exercise", "Exercise 3–5 times a week" and so on) so you can match it to your week.
3. Set a goal: Maintain, Lose (−500 kcal) or Gain (+300 kcal). The target calorie intake and the macro grams follow that choice.
4. Read the right card: your BMI and category, your position on the gauge, the healthy weight range, BMR, TDEE, target intake and grams of carbs, protein and fat.
5. Press Copy results to copy your inputs and results as text. Nothing is saved — reopening the page brings back the example values.

Asian BMI cut-offs are stricter than WHO's

BMI is your weight in kilograms divided by your height in meters squared. The WHO calls 25+ overweight and 30+ obese, but studies of East Asian populations show higher body fat and earlier diabetes and hypertension risk at the same BMI, so the Korean Society for the Study of Obesity uses 23 for overweight and 25 for obese. This BMI calculator applies those Asian cut-offs: underweight below 18.5, normal 18.5–22.9, overweight 23–24.9, obese class 1 25–29.9, class 2 30–34.9, class 3 35 and above. If another site says "normal" and this one says "overweight", that is why. The tick marks on the gauge — 18.5, 23, 25 and 30 — are exactly those boundaries, and the healthy weight range is the weight that would give you a BMI of 18.5 and 22.9.

BMR and TDEE explained

Basal metabolic rate is the minimum energy your body burns lying still all day — breathing, keeping warm. We use the Mifflin-St Jeor equation (1990), generally considered the most accurate: men 10×weight + 6.25×height − 5×age + 5; women end with −161. Multiply by an activity factor (1.2–1.9) to get your TDEE, the calories that keep your current weight. Desk job with no exercise: 1.2. Light exercise 1–3 times a week: 1.375. Three to five sessions: 1.55. Almost daily: 1.725. Physical labor or two-a-days: 1.9. Most people overestimate their activity, so picking one level lower is the safer bet.

A worked example

A 30-year-old man at 170 cm and 65 kg has a BMI of 65 ÷ 1.7² = 22.5, in the normal band, and a healthy weight range of 53.5–66.2 kg. His BMR is 10×65 + 6.25×170 − 5×30 + 5 = 1,568 kcal. With "Lightly active" (×1.375) his TDEE is 2,155 kcal, and switching the goal to Lose gives a target of 1,655 kcal. Split 50/25/25 and converted at 4 kcal per gram for carbs and protein and 9 for fat, that is 207 g carbs, 103 g protein and 46 g fat a day. Change only the sex to female and the BMR drops to 1,402 kcal.

Why −500 to lose and +300 to gain

A kilogram of body fat holds about 7,700 kcal, so a 500 kcal daily deficit loses roughly 0.5 kg a week or 2 kg a month. Faster than that and you risk losing muscle and rebounding. For gaining, surplus calories go to fat more easily than muscle, so a modest +300 is the usual recommendation. If your target drops below your BMR the calculator warns you — do not stay under it for long.

The messages under your BMI

Three situations produce a line under the result. If your target intake is below your BMR you get a warning not to sustain it for long; if you are underweight but chose the weight-loss goal you get a warning to rethink the goal. Both appear in red. If you are simply outside the healthy band, the line tells you how far you are from its nearest edge — "+3.2 kg to reach the healthy range" or "−4.1 kg". If height, weight or age is missing, the results are replaced by a prompt to fill them in.

What BMI cannot tell you

BMI does not distinguish fat from muscle. A long-time lifter with low body fat can read over 25 and be labeled "obese", while someone with a normal BMI but high body fat slips through. Waist circumference (abdominal obesity at 90 cm for men, 85 cm for women by Korean criteria) or a body-composition scan gives a fuller picture. The 50/25/25 macro split is a general starting point too: if you are building muscle, raise protein to 1.6–2 g per kilogram of body weight and cut carbs by the same amount.

Frequently asked questions

Why is the healthy range 18.5–22.9 rather than 18.5–24.9?

Because the Korean and Asian cut-off for overweight is 23, not 25. The upper end of the range is set just under it, at 22.9, so at 170 cm the healthy band runs from 18.5×1.7² = 53.5 kg to 22.9×1.7² = 66.2 kg.

Why do women subtract 161?

The Mifflin-St Jeor equation was fitted separately to men and women, and −161 versus +5 is the resulting constant. For the same height, weight and age it puts a woman's BMR 166 kcal lower, reflecting higher average body fat and lower muscle mass.

Can I change the macro split?

Not in this calculator — it is fixed at 50% carbs, 25% protein, 25% fat. To use a different split, multiply your target calories by the share you want and divide by 4 for carbs or protein and by 9 for fat. On 2,000 kcal, 30% protein is 2,000 × 0.3 ÷ 4 = 150 g.

I know my height in feet and inches and my weight in pounds

The form takes centimeters and kilograms only. Convert with 1 ft = 30.48 cm, 1 in = 2.54 cm and 1 lb = 0.4536 kg, or use the unit converter linked below and copy the numbers across.

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