Body Metrics Calculator

Calculate BMI, BMR, TDEE, body fat, ideal weight, healthy weight range and daily calorie and macro targets from height, weight, age, sex and activity level. It runs offline with no API key and no scraping, so every run returns the same numbers and nothing breaks when a website changes.

Give it one person or a whole list. You get one clean row per person with every metric filled in.

What you get for each person

• BMI and the WHO weight category, plus BMI prime and the Ponderal index.
• The healthy weight range for that height, in kilograms.
• BMR from two formulas: Mifflin-St Jeor and the revised Harris-Benedict. Katch-McArdle is added when body measurements are supplied.
• TDEE, your maintenance calories, using the activity level you set.
• Body fat percent. If you give waist and neck (and hip for women), it uses the US Navy method. Otherwise it estimates from BMI with the Deurenberg formula.
• Lean body mass and fat mass in kilograms.
• Ideal weight from four formulas: Devine, Robinson, Miller and Hamwi.
• Daily calorie targets to lose, maintain or gain, at two rates each.
• A starting macro split at maintenance: protein, carbohydrate and fat in grams.

Input

Pass a people array. Each item is one person:

{
  "people": [
    {
      "label": "Alex",
      "units": "metric",
      "sex": "male",
      "age": 30,
      "height": 180,
      "weight": 82,
      "activity": "moderate",
      "waist": 88,
      "neck": 38
    }
  ]
}

Fields:

• label: any name or id you want on the row. Optional.
• units: metric or imperial. Metric reads height in centimetres and weight in kilograms. Imperial reads height in inches and weight in pounds. Waist, neck and hip follow the same unit.
• sex: male or female. Needed for the BMR, body fat and ideal weight formulas.
• age: age in years.
• height, weight: the two required measurements.
• activity: one of sedentary, light, moderate, active, very_active. Sets the TDEE multiplier from 1.2 to 1.9. Defaults to moderate.
• waist, neck, hip: optional. Add them to switch body fat to the US Navy method. Women also need hip.

Leave people empty and the run uses two example people so you can see the output shape right away.

Output

One row per person. The table view shows the headline columns (BMI, BMR, TDEE, body fat, ideal weight and the three calorie targets). The full row also carries BMI prime, the Ponderal index, the healthy weight range, both BMR formulas, lean and fat mass, all four ideal weight formulas, both mild and standard calorie targets, and the macro split. A row that fails validation keeps its label and carries an error message instead of numbers.

How the numbers are worked out

• BMI is weight in kilograms divided by height in metres squared. Categories follow the WHO cut points.
• Mifflin-St Jeor is the default BMR and drives TDEE, because it tracks measured resting energy better than Harris-Benedict for most adults.
• The US Navy body fat method uses tape measurements, so it beats a BMI estimate when you supply them.
• Calorie targets sit 250 and 500 kcal below or above maintenance, and never drop below 1200 kcal.

A note on use

These numbers are estimates for general information, not medical advice. BMI, body fat formulas and calorie targets are population averages and do not account for muscle mass, pregnancy, athletes or clinical conditions. Talk to a doctor or a registered dietitian before making changes to diet or training.