Weight Calculator

What is IBW, and what does this calculator actually show you

IBW stands for Ideal Body Weight. It is an estimate of what a healthy adult of a given height and gender is expected to weigh, based on formulas doctors and pharmacists have used since the 1960s, originally to work out safe drug dosages rather than to judge how someone looks. IBW only needs two inputs, your height and your gender, which is exactly why it spread far beyond its original medical use into general fitness and health tracking. See the IBW formula page for the full history and the exact equation behind each formula, worked out step by step.

This calculator runs four of the most widely used IBW formulas side by side (Hamwi, Devine, Robinson and Miller) rather than picking just one, because each formula was built from a different research sample and they do not always agree. Averaging all four gives you a single, more balanced number instead of anchoring on whichever formula you happened to look up first. It also shows a fifth reference point, the WHO healthy-BMI weight range for your exact height, and if you enter your current weight, tells you plainly whether you fall below, within, or above that range.

Four worked examples

Real calculations using the exact formulas this calculator runs, so you can sanity-check your own result:

1. 170 cm (5'7") male: Hamwi 66.7 kg, Devine 65.9 kg, Robinson 65.2 kg, Miller 66.0 kg. Average 65.9 kg (145.4 lb). WHO healthy range for this height: 53.5-72.3 kg (118-159 lb).
2. 5'3" (160 cm) female: Hamwi 52.1 kg, Devine 52.4 kg, Robinson 54.1 kg, Miller 57.2 kg. Average 53.9 kg (118.9 lb). WHO healthy range for this height: 47.4-64.0 kg (104-141 lb).
3. 5'10" (178 cm) male: Hamwi 75.0 kg, Devine 73.0 kg, Robinson 71.0 kg, Miller 70.3 kg. Average 72.3 kg (159.4 lb). WHO healthy range for this height: 58.5-79.0 kg (129-174 lb).
4. 5'4" (163 cm) female: Hamwi 54.3 kg, Devine 54.7 kg, Robinson 55.8 kg, Miller 58.5 kg. Average 55.8 kg (123.1 lb). WHO healthy range for this height: 48.9-66.1 kg (108-146 lb).

Why the four formulas do not agree with each other

Every IBW formula follows the same basic shape: a base weight for a height of exactly 5 feet, plus a fixed amount added for every inch taller than that. What differs is the base weight and the per-inch increment, because each formula came out of a different study, decades apart, using different reference populations. The Devine formula (1974) is the most widely cited today, largely because hospitals adopted it for calculating drug doses by body weight and it stuck. The Robinson formula (1983) and Miller formula (1983) are both later attempts to refine Devine's numbers using newer height-and-weight data, and they tend to land closer together than they do to Hamwi, the oldest of the four, from 1964.

None of the four is objectively the correct one. They are four different research teams' best estimate of the same underlying idea, which is exactly why this calculator shows all four instead of hiding three of them behind a single formula and pretending the disagreement does not exist. The gap between the highest and lowest of the four estimates is usually a few kilograms, and the average is a reasonable middle ground if you just want one number.

Ideal weight for common heights in India

Height-and-weight searches from India often ask about specific, round heights like 5'4", 5'6" or 170 cm, since these are common reference points on ID documents and school health records. A 170 cm (5'7") male, one of the more frequently searched heights, lands at an average ideal weight of roughly 66 kg across the four formulas, comfortably inside the WHO healthy range of 53.5 to 72.3 kg for that height. A 160 cm (5'3") female lands at roughly 54 kg on average, inside a healthy range of 47.4 to 64.0 kg. These are population averages, not individual verdicts. Frame size, muscle mass and age all shift where a specific person should realistically sit within that range, which is exactly why the calculator shows a range rather than a single hard cutoff.

It is also worth being clear about what this calculator is not. It estimates ideal weight for an adult using the four formulas above. It does not compute the age-and-sex-specific growth percentile figures used to track a child's or teenager's weight-for-age in India, which follow a completely different reference dataset (typically WHO or IAP growth charts) and are usually plotted by a pediatrician rather than looked up from a fixed formula. If you are trying to check a child's growth rather than an adult's ideal weight, a pediatric growth-chart tool is the right one to use instead of this calculator.

Ideal weight compared to BMI and other measures

IBW and BMI answer slightly different questions using the same two inputs. BMI (Body Mass Index) takes your actual height and weight and tells you which category you currently fall into (underweight, normal, overweight, obese). IBW takes only your height and gender and tells you what a healthy weight target would look like before you even enter a current weight. This calculator uses the WHO's 18.5-25 healthy BMI range to build the weight-range reference shown alongside the four formulas, so the two approaches line up rather than contradict each other. If you want a plain BMI reading with the full WHO classification table, a dedicated BMI calculator covers that specific case in more depth than an IBW tool needs to.

Other measures researchers sometimes prefer include waist-to-height ratio (waist circumference divided by height, which captures where fat is carried rather than just total weight) and body fat percentage (measured with calipers, a bioelectrical impedance scale, or a DEXA scan, which measures fat mass directly). Neither is built into this calculator on purpose, since both need a measurement beyond height and weight. IBW's real advantage is that it takes ten seconds and needs nothing more than a height and a gender, which is why it remains a fast first-pass reference point even though it is not the final word on anyone's health.

How to use the current-weight comparison

The weight field above the calculator is optional. Leave it blank and you get the four IBW formulas plus the WHO healthy range for your height, nothing else. Fill it in and the calculator adds one more line telling you whether that weight sits below, within, or above the healthy range for your height. This is deliberately a simple three-way read rather than a fine-grained score, because a single number a few kilograms outside the range is a very different situation from one that is far outside it, and this calculator is not trying to diagnose anything. It is a starting point for a conversation with a doctor or dietitian, not a replacement for one.

A result outside the healthy range is not automatically a problem. Athletes and very muscular people in particular can carry a current weight above the range shown here while having very little body fat, because none of these formulas (or BMI, for that matter) can tell the difference between muscle and fat. Age, pregnancy, and certain medical conditions also change what a healthy target weight looks like for a specific person in ways a generic formula cannot capture.

Imperial or metric, your choice

Click Imperial or Metric above the calculator to switch units at any time. Imperial mode uses feet and inches for height and pounds for weight. Metric mode uses centimeters and kilograms. Every result is shown in both units regardless of which mode you are in (for example, "65.9 kg (145.4 lb)"), so you never have to convert by hand to compare against a chart or a scale that uses the other system. See the height and weight chart for a quick-lookup table across a full range of heights if you would rather scan a table than type in your own numbers.