Ideal Weight Calculator
Find out what your ideal weight is for your height and age. Uses Devine, Robinson, Miller, and Hamwi formulas with frame size adjustment.
"Ideal weight" is a range, not a single number. This calculator uses four established clinical formulas - Devine, Robinson, Miller, and Hamwi - to give you a range of estimates based on your height and sex, then adjusts for body frame size. It also shows the BMI-based healthy weight range (BMI 18.5-24.9) for comparison. The output covers both metric (kg) and imperial (lbs) so UK and US users get matching numbers.
For informational purposes only. Not a substitute for professional medical advice. Consult a healthcare provider before making changes to your diet or exercise routine.
About Ideal Weight Calculator
Where Do These Formulas Come From?
All four formulas were originally designed for clinical dosing, not for personal weight goals. Ben J. Devine published his equation in 1974 to help pharmacists dose the antibiotic gentamicin in obese patients - the number it produces is a drug-distribution proxy, not a health target. Robinson (1983), Miller (1983), and Hamwi (1964) followed with tweaks based on different reference populations. All four are still embedded in modern hospital protocols for drug dosing, mechanical ventilator tidal volume, and renal function estimates, which is why they remain the standard reference even with known limitations.
The Four Ideal Weight Formulas
Each formula was developed from different population data at different times. Showing all four gives a realistic range rather than a misleadingly precise single number.
| Formula | Year | Men (kg) | Women (kg) |
|---|---|---|---|
| Devine | 1974 | 50.0 + 2.3 per inch over 5 ft | 45.5 + 2.3 per inch over 5 ft |
| Robinson | 1983 | 52.0 + 1.9 per inch over 5 ft | 49.0 + 1.7 per inch over 5 ft |
| Miller | 1983 | 56.2 + 1.41 per inch over 5 ft | 53.1 + 1.36 per inch over 5 ft |
| Hamwi | 1964 | 48.0 + 2.7 per inch over 5 ft | 45.5 + 2.2 per inch over 5 ft |
Worked example (male, 5'10" / 178 cm): That is 10 inches over 5 feet.
| Formula | Calculation | Result |
|---|---|---|
| Devine | 50.0 + (2.3 x 10) | 73.0 kg (161 lbs) |
| Robinson | 52.0 + (1.9 x 10) | 71.0 kg (157 lbs) |
| Miller | 56.2 + (1.41 x 10) | 70.3 kg (155 lbs) |
| Hamwi | 48.0 + (2.7 x 10) | 75.0 kg (165 lbs) |
The range across all four formulas is 70.3-75.0 kg. The variation reflects the reality that "ideal weight" depends on body composition, not just height. For reference, a BMI of 22 at 178 cm gives 69.7 kg, BMI 24 gives 76.0 kg, and BMI 25 (the overweight cut-off) gives 79.2 kg - so all four formula outputs sit inside the BMI "healthy" band.
Imperial Worked Example (5'6" Female, Medium Frame)
Take a 5'6" woman - 6 inches over 5 ft, or 168 cm. Medium frame so no adjustment. The formulas produce:
| Formula | Calculation | Result |
|---|---|---|
| Devine | 45.5 + (2.3 x 6) | 59.3 kg (131 lbs) |
| Robinson | 49.0 + (1.7 x 6) | 59.2 kg (130 lbs) |
| Miller | 53.1 + (1.36 x 6) | 61.3 kg (135 lbs) |
| Hamwi | 45.5 + (2.2 x 6) | 58.7 kg (129 lbs) |
Range: 58.7-61.3 kg (129-135 lbs). A large-framed woman of the same height would be around 64-67 kg; a small-framed woman around 53-55 kg. The BMI healthy band for 168 cm is 52-70 kg - wider than the formula output, as expected.
Ideal Weight Ranges by Height
| Height | Men (formula range) | Women (formula range) | BMI 18.5-24.9 range |
|---|---|---|---|
| 5'0" / 152 cm | 50-56 kg (110-124 lbs) | 45-53 kg (100-117 lbs) | 43-58 kg (95-128 lbs) |
| 5'4" / 163 cm | 59-67 kg (130-147 lbs) | 52-62 kg (115-136 lbs) | 49-66 kg (108-146 lbs) |
| 5'8" / 173 cm | 67-77 kg (148-170 lbs) | 60-71 kg (132-156 lbs) | 55-74 kg (122-164 lbs) |
| 6'0" / 183 cm | 75-86 kg (166-190 lbs) | 67-80 kg (148-176 lbs) | 62-84 kg (137-184 lbs) |
| 6'4" / 193 cm | 84-97 kg (186-214 lbs) | 76-89 kg (168-197 lbs) | 69-93 kg (152-205 lbs) |
How Does Frame Size Affect Ideal Weight?
Body frame size accounts for differences in bone structure. A person with a large frame naturally weighs more than someone of the same height with a small frame, even at the same body fat percentage.
| Frame Size | Wrist Test | Weight Adjustment |
|---|---|---|
| Small | Thumb and middle finger overlap when wrapped around wrist | Subtract ~10% from base estimate |
| Medium | Thumb and middle finger just touch | Use base estimate |
| Large | Thumb and middle finger do not touch | Add ~10% to base estimate |
Example: If the Devine formula gives 73 kg for a medium-frame male at 5'10", a large frame would adjust to about 80 kg and a small frame to about 66 kg.
Limitations of Ideal Weight Formulas
| Limitation | Why It Matters |
|---|---|
| Based on population averages | Does not account for individual body composition or muscle mass |
| Developed decades ago | Populations have changed since the 1960s-1980s |
| Height-based only | Two people of the same height can have very different builds |
| No age adjustment | Body composition changes with age |
| Originally designed for drug dosing | The Devine formula was created for medication dosages, not health targets |
| Limited ethnic diversity in studies | Original studies were predominantly white Western populations |
These formulas are useful as rough reference points, not as medical targets. A muscular 80 kg person at 12% body fat is healthier than a sedentary 73 kg person at 30% body fat, even though the formulas would say the lighter person is closer to "ideal." Body composition matters more than a number on the scale.
Context: How Common Is Overweight in the UK and US?
Most adults in both countries now sit above the BMI healthy range, which is one reason "ideal" from a formula can feel far from the everyday. According to NHS England's Health Survey for England 2024, 30% of adults aged 16+ in England were living with obesity and 66% were overweight or obese combined. Prevalence rose with age, peaking at 35-36% among 55-74 year olds. In the US, CDC data for 2021-2023 (NCHS Data Brief 508) put adult obesity prevalence at 40.3% overall - 39.2% in men and 41.3% in women - with the highest regional rates in the Midwest (35.9%) and South (34.5%).
| Population | Overweight or obese | Obese only | Source |
|---|---|---|---|
| England adults 16+ (2024) | 66% | 30% | NHS Digital HSE 2024 |
| Scotland adults | 66% | ~32% | Scottish Health Survey |
| US adults 20+ (2021-23) | ~73% | 40.3% | CDC NCHS Data Brief 508 |
| US adults 40-59 | - | 46.4% | CDC NCHS Data Brief 508 |
These numbers are not a target - they are background. If the calculator tells you your "ideal" is 20 kg below your current weight, you are not unusual. The gap between statistical "ideal" and real-world average is large almost everywhere.
Common Mistakes When Using Ideal Weight Numbers
- Treating one formula as the "right" answer. The four formulas disagree by 5-7 kg at most heights. Use the range, not a single figure.
- Ignoring body composition. Two people at 75 kg and 5'10" can have very different health profiles - one at 15% body fat, the other at 32%. The formula says nothing about that.
- Applying the formulas to teenagers. These equations were built for adults. Growth-chart percentiles from the WHO or CDC are more appropriate under 18.
- Forgetting the frame-size adjustment. A large-framed person at the unadjusted Devine weight will look underweight. A small-framed person will look heavier than optimal. The ~10% frame shift matters.
- Using drug-dosing weights as fitness targets. Devine was invented for gentamicin. The number is useful clinically, not as a bathroom-scale goal.
Ideal Weight vs Healthy Weight
"Ideal weight" from these formulas and "healthy weight" from BMI are related but different concepts. The BMI-based range (18.5-24.9) is wider and represents the weight range where population-level health risks are statistically lowest. The formula-based "ideal" is a narrower estimate of what might be optimal.
A more complete picture comes from combining multiple measures: scale weight, body fat percentage, waist circumference, and general fitness. The Body Fat Calculator estimates your fat-to-lean ratio using the US Navy method, and the BMI Calculator provides the standard height-weight screening. Waist-to-height ratio is increasingly cited as a simpler predictor of cardiometabolic risk than BMI - NICE's 2023 guideline NG246 recommends keeping waist circumference under half of height for adults.
Using Your Ideal Weight
If your current weight is significantly different from the calculated range and you want to make changes, these tools can help:
- Calorie Deficit Calculator - plan a timeline for reaching your target weight
- TDEE Calculator - find your daily calorie needs at your current weight
- Protein Calculator - ensure adequate protein to preserve muscle during weight loss
A realistic, sustainable pace of weight change is 0.25-1% of body weight per week - roughly 0.2-0.8 kg for an 80 kg adult. Faster than that risks muscle loss, which the protein and resistance-training tools above help protect against. The NHS Better Health programme and the US Dietary Guidelines 2020-2025 both anchor on the same range: 0.5-1 kg (1-2 lbs) per week for sustained change.
When These Formulas Do Not Apply
A few cases where the four formulas break down and should not be used as a personal target:
- Athletes and heavily muscled individuals. Rugby forwards, power lifters, and bodybuilders routinely sit 10-25 kg above the formula output with single-digit body fat. Use body-fat measurement instead.
- Pregnancy and post-partum. Weight during and immediately after pregnancy should be guided by the Institute of Medicine 2009 gestational weight gain ranges, not a static formula.
- Older adults (65+). Being slightly above BMI 25 is associated with lower mortality in this group per multiple meta-analyses - the so-called "obesity paradox." Do not push for the formula number at the cost of muscle mass.
- Short stature (under 5 ft / 152 cm). The "per inch over 5 ft" structure means the formulas extrapolate below the height they were designed for. ClinCalc and most pharmacy references flag output under 5 ft as unreliable.
- Amputees and people with significant limb differences. Adjust using standard limb-proportion corrections (e.g. subtract ~16% for a full leg) before using any ideal-weight reading.
For most of the general adult population between 5 ft and 6'4", the range these four formulas produce is a useful sanity check against the BMI band and personal goals - nothing more, nothing less.
All calculations happen in your browser. No personal data is collected, stored, or transmitted.
Sources
- NHS Digital - Health Survey for England 2024: Adults' overweight and obesity
- CDC NCHS Data Brief 508 - Obesity and Severe Obesity Prevalence in Adults
- CDC - Adult Obesity Prevalence Maps
- NICE NG246 - Overweight and obesity management
- WHO - Obesity and Overweight Fact Sheet
- PMC - Evaluation of Methods Used to Calculate Ideal Body Weight
Frequently Asked Questions
How is ideal weight calculated?
This calculator uses four established medical formulas (Devine, Robinson, Miller, and Hamwi) that estimate ideal body weight based on height and gender. Each formula was developed from different population studies and produces slightly different results, giving you a range rather than a single number.
What does frame size mean?
Frame size refers to your bone structure. You can estimate it by wrapping your thumb and middle finger around your wrist. If they overlap, you have a small frame. If they just touch, medium. If they do not touch, large. Frame size adjusts the ideal weight estimate by roughly 10 percent in either direction.
Is ideal weight the same for everyone of the same height?
No. Ideal weight depends on many factors including muscle mass, bone density, body composition, age, and overall health. These formulas provide general guidelines based on population averages, not personalised medical targets.
Should I aim for the exact ideal weight shown?
These numbers are reference points, not strict targets. A healthy weight falls within a range. The BMI-based healthy range shown alongside the formula results gives additional context. Focus on overall health markers rather than hitting an exact number on the scale.
Why do the formulas give different results?
Each formula was developed using different study populations and methodologies at different times. The variation between them reflects the inherent uncertainty in defining a single ideal weight. The range across all formulas gives a more realistic picture than any single number.
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