---
title: "Calculate Body Mass Index (BMI) from weight and height using the WHO standard formula. Supports metric (kg/cm) and imperial (lbs/inches) units. Returns the BMI value, WHO classification (Underweight, Normal, Overweight, Obese Class I-III), and the healthy weight range for the given height. Formula: BMI = weight_kg / (height_m)^2. Useful for health screening, fitness planning, and clinical intake forms."
method: POST
path: "/api/bmi_calculator"
tags: ["general"]
---

# Calculate Body Mass Index (BMI) from weight and height using the WHO standard formula. Supports metric (kg/cm) and imperial (lbs/inches) units. Returns the BMI value, WHO classification (Underweight, Normal, Overweight, Obese Class I-III), and the healthy weight range for the given height. Formula: BMI = weight_kg / (height_m)^2. Useful for health screening, fitness planning, and clinical intake forms.

`POST /api/bmi_calculator`

## Request

- Base URL: `https://calc.engineer`
- URL: `https://calc.engineer/api/bmi_calculator`
- Auth: none declared

## Request body

- object
  - `weight` number, required: Body weight. Units determined by the 'unit' parameter.
  - `height` number, required: Height. Units determined by the 'unit' parameter.
  - `unit` 'metric' | 'imperial': Unit system. 'metric' = kg and cm. 'imperial' = lbs and inches. Defaults to 'metric'.

## Response `200`

Computed result for bmi_calculator

- object
  - `result` object, required
    - `bmi` number, required: Body Mass Index value rounded to 1 decimal.
    - `category` string, required: WHO BMI classification: Underweight, Normal weight, Overweight, Obese Class I/II/III.
    - `healthy_weight_range_low` number, required: Low end of healthy weight range (BMI 18.5) in the input unit system.
    - `healthy_weight_range_high` number, required: High end of healthy weight range (BMI 24.9) in the input unit system.
    - `weight_unit` string, required: Unit of the weight values in this response (kg or lbs).
  - `tool` string, required
  - `version` string, required
  - `computed_at` string, date-time, required
  - `chain` object, required
    - `feeds` unknown[]
      - unknown
    - `accepts_from` unknown[]
      - unknown

## Other responses

- `400`: Validation error or invalid JSON
- `404`: Tool not found

---

[API](https://skmtc.dev/calc/apis/calc-engineer-api.md) · [All operations](https://skmtc.dev/calc/apis/calc-engineer-api/llms.txt) · [OpenAPI document](https://skmtc.dev/calc/apis/calc-engineer-api/revisions/8830480ec488?raw)