# BMI and calorie calculator

Written on 4 November 2026 by Ratio. Every example was run through Ratio that day.

Weight and height give your BMI. Add your age and how active you are, and Ratio works out the calories you burn in a day, with the Mifflin–St Jeor formula.

## Body mass index

| bmi(80 kg, 180 cm) | 24.7 |
| --- | --- |
| bmi(70 kg, 1.75 m) | 22.9 |
| bmi(180 lb, 5 ft 11 in) | 25.1 |

Under 18.5 is underweight, 18.5 to 25 a healthy weight, 25 to 30 overweight, and 30 or more obesity. BMI can't tell muscle from fat, so read it as a rough guide.

## Calories a day

| bmr 80 kg 180 cm 30 years male | 1,780 kcal |
| --- | --- |
| tdee 80 kg 180 cm 30 years male moderate | 2,759 kcal |
| tdee 65 kg 165 cm 35 years female light | 1,850 kcal |

BMR is what your body burns at rest. TDEE multiplies it by how active you are: sedentary, light, moderate, active or very active.

## Losing or gaining

| keep = tdee 80 kg 180 cm 30 years male moderate | 2,759 kcal |
| --- | --- |
| keep - 500 | 2,259 kcal |
| keep + 300 | 3,059 kcal |

About 500 kcal a day under your TDEE is a common way to lose weight slowly. For running paces and heart rate zones, see the [fitness calculator](https://useratio.app/fitness-calculator).

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## Questions

**What is a healthy BMI?** For adults, 18.5 to 24.9. It is the same for men and women, but it isn't meant for children, pregnancy or very muscular people.

**What is the difference between BMR and TDEE?** BMR is the energy you use at complete rest. TDEE adds everything you do in a day, so it is roughly what you can eat to keep your weight.

**Can I use pounds and feet?** Yes. Switch the calculator to US units, or type “bmi(180 lb, 5 ft 11 in)” in Ratio.

Source: https://useratio.app/bmi-calculator