Ideal Weight Calculator
Ideal weight calculator: your ideal weight from five classic formulas, with the healthy BMI range and frame size. Free, no sign-up, and it runs in your browser.
Dedicated page: /en/ideal-weight-calculator
Estimate only, not medical advice. Ideal weight formulas give a reference range, not a target you must hit: muscle, bone density and frame all shift a healthy weight. They are for adults only.
Adults only. The formulas do not change with age, but the BMI-for-age row does for ages 20 and under, which this tool does not cover.
Judge frame from wrist size: measure your wrist and compare it with the table below.
22 is a common mid-range target inside the healthy 18.5 to 24.9 band.
Quick answer
An ideal weight calculator works out your ideal body weight from your height and sex using the Devine, Robinson, Miller, Hamwi and Lorentz formulas. It also shows the healthy weight range from BMI, adjusts for frame size, and tells you how far your current weight sits from that range.
About this Ideal Weight Calculator
Ideal weight calculator: your ideal weight from five classic formulas, with the healthy BMI range and frame size. It is one of the Health and Family on ToolUstad, and like every tool here it runs entirely in your browser: nothing you type, paste or open is uploaded to a server, and there is no sign-up or usage limit.
What is an ideal weight calculator?
An ideal weight calculator estimates a healthy weight from height and sex alone, using formulas published between 1964 and 1983. Each formula starts from a base weight for someone 5 feet tall and adds a fixed amount for every inch above that. A 5 ft 6 in woman gets 59.3 kg from Devine, 59.2 kg from Robinson, 61.3 kg from Miller and 58.7 kg from Hamwi. The range is the answer, not any single number.
The five formulas
Hamwi, from 1964, was built for quick drug dosing estimates: 48 kg plus 2.7 kg per inch for men, 45.5 kg plus 2.2 kg per inch for women. Devine, from 1974, was built for gentamicin dosing and is the most widely cited: 50 kg plus 2.3 kg per inch for men, 45.5 kg plus 2.3 for women. Robinson and Miller, both from 1983, refined Devine with slightly different base weights and per-inch amounts. The Peterson formula works differently: it takes a target BMI, 22 by default, and returns the weight at that BMI.
The healthy BMI range
Body mass index is weight in kilograms divided by height in metres squared. The healthy range is 18.5 to 24.9, by the CDC and the WHO. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 and over is obese. BMI does not measure body fat, so a muscular person can read as overweight while carrying little fat.
Frame size and the wrist test
Real frames vary, so the calculator adjusts the formula results by 10% either way: a small frame trims them, a large frame adds. The usual way to judge frame is wrist circumference relative to height. For women, under 5.5 inches is a small frame, 5.5 to 6.5 is medium, and over 6.5 is large. For men, under 6.5 is small, 6.5 to 7.5 is medium, and over 7.5 is large. Enter your wrist measurement and the tool tells you which frame it suggests.
How to use the result
Read the formula range first, then the healthy BMI range, then your current BMI and where it sits. A 150 lb woman at 5 ft 6 in has a BMI of 24.2, inside the healthy range and 2.0 kg below its top, even though she is above the formula range: that is normal, and the BMI range is the better guide. Set a target BMI inside 18.5 to 24.9, 22 is a common mid-range choice, and the tool gives the weight at that BMI.
Best practices
- Use the healthy BMI range as your main guide, and the formulas as a cross-check.
- Adjust for frame size before you judge the number: a large frame adds 10%.
- Pair the result with body fat percent: muscle weighs more than fat, and BMI cannot see the difference.
Common mistakes
- Treating one formula number as a target you must hit exactly.
- Using the formulas below 5 feet tall, or for children: they are not validated there.
- Ignoring muscle: a lifter can be healthy above the formula range and still be lean.
Learn: how to use the Ideal Weight Calculator
- Enter your sex, height and current weight.
- Pick your frame size, or enter your wrist measurement to judge it.
- Set a target BMI inside the healthy 18.5 to 24.9 band.
- Read the formula range, the healthy BMI range, and how far you sit from it.
Features
- Devine, Robinson, Miller, Hamwi and Lorentz formulas side by side
- Healthy BMI range of 18.5 to 24.9 for your exact height
- Peterson formula at your target BMI
- Frame size adjustment of plus or minus 10%
- Wrist measurement guide for judging frame size
- Current BMI and category, with distance from the healthy range
- Ideal weight by height chart for men and women
- Metric and imperial units, with conversion when you switch
Worked example
A 35-year-old woman, 5 ft 6 in tall: the Devine formula gives 59.3 kg (130.7 lb), Robinson 59.2 kg, Miller 61.3 kg and Hamwi 58.7 kg, a range of 58.7 to 61.3 kg. The healthy BMI range for her height is 52.0 to 70.0 kg (114.6 to 154.3 lb), and a target BMI of 22 gives 61.8 kg (136.3 lb). At 150 lb (68.0 kg) her BMI is 24.2, inside the healthy range and 2.0 kg below its top.
Frequently asked questions
What is ideal body weight?
A reference weight worked out from height and sex, using formulas from the 1960s to 1980s. The four classic formulas give a narrow range, not one magic number. The healthy BMI range is usually the more useful guide, because it is wider and matches what public health bodies use.
Which formula is the most accurate?
Devine is the most widely cited and the most medically validated, but it was built for drug dosing in hospitals, not for setting a weight goal. Robinson, Miller and Hamwi give similar numbers, within a few pounds, which is why the tool shows all of them.
Why do the formulas disagree?
Each was built from a different population and purpose, with different base weights and per-inch amounts. Devine adds 2.3 kg per inch over 5 feet for both sexes, Robinson adds 1.9 for men and 1.7 for women, Miller adds 1.41 and 1.36, and Hamwi adds 2.7 and 2.2. The spread is the honest answer.
What is a healthy BMI?
18.5 to 24.9 for adults, by the CDC and WHO. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 and over is obese. BMI does not measure body fat, so muscular people can read as overweight while carrying little fat.
How does frame size change the result?
The common clinical convention is plus or minus 10%: a small frame trims the formula result by 10%, a large frame adds 10%. Judge frame from wrist size relative to height, using the wrist guide in the tool.
Do the formulas work for children or short adults?
No. They were built for adults 5 feet and taller, and the per-inch maths loses accuracy below that height. For shorter adults, use the healthy BMI range. For children, use CDC BMI-for-age percentiles, not these formulas.
Should I aim for the ideal weight number?
Treat it as a reference, not a target you must hit. Muscle mass, bone density and frame all shift a healthy weight by 10 to 15 lb either way. The healthy BMI range, your body fat percent and how you feel matter more than one formula number.
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