# Ideal Weight Calculator

URL: https://speedycalculator.com/calculators/health/ideal-weight/
Last updated: 2026-10-25

> The ideal weight calculator estimates a reference body weight from height and sex using the Devine formula, with the Robinson formula and the midpoint of the healthy BMI range for comparison. Clinicians use these values mainly for drug dosing, not as personal weight goals.

## Inputs

- Sex
- Height (cm, m, in, ft)

## Results

- Ideal weight (Devine)
- Robinson formula
- BMI 18.5–24.9 midpoint

## Formula

```
Devine: men 50 kg + 2.3 kg × (inches over 60); women 45.5 kg + 2.3 kg × (inches over 60)
Robinson: men 52 + 1.9 × (in − 60); women 49 + 1.7 × (in − 60)
```

## Explanation

“Ideal body weight” formulas were created in the 1970s and 1980s, largely to standardise medication doses. They are simple linear functions of height and ignore frame size, muscle and age.

### How to use it

Choose your sex and enter your height. Compare the three results: they usually agree within a few kilograms.

### Limitations

These formulas are less reliable for people shorter than about 152 cm (5 ft) and do not describe what is healthy for an individual. A healthy weight is better thought of as a range; see the BMI calculator.

### Inputs explained

FieldWhat to enterSexChoose one: Male, FemaleHeightUnits: cm, m, in, ft

### What each result means

- **Ideal weight (Devine)** = [Sex] + 2.3 × ([Height in inches] - 60)
- **BMI 18.5–24.9 midpoint** = 21.7 × ([Height]÷100)^2

## Worked example

Man, 170 cm = 66.93 in, so 6.93 in over 5 ft.

Devine = 50 + 2.3 × 6.93 ≈ **65.9 kg**.

Robinson = 52 + 1.9 × 6.93 ≈ 65.2 kg. BMI 21.7 midpoint = 21.7 × 1.70² ≈ 62.7 kg.

## Key terms

- **Ideal body weight (IBW)**: A height-based reference weight used in clinical dosing.
- **Devine formula**: The most widely used IBW equation, published in 1974.
- **Lean body weight**: Body weight minus fat mass; a different concept from IBW.

## FAQ

**Should I aim for my ideal body weight?**
Not necessarily. It is a reference value; a healthy range and how you feel matter more.

**Why do formulas differ?**
Each was fitted to different data sets and goals.

**Does frame size matter?**
Yes, but these formulas do not account for it.

**What formula does the Ideal Weight Calculator use?**
Devine: men 50 kg + 2.3 kg × (inches over 60); women 45.5 kg + 2.3 kg × (inches over 60).


## Sources

- Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm, 1974
- Robinson JD et al. Determination of ideal body weight for drug dosage calculations. Am J Hosp Pharm, 1983