Ideal Weight Calculator
Calculate your ideal body weight using seven medically validated formulas and find your healthy weight range based on BMI.
Your Results
Robinson Formula
Miller Formula
Hamwi Formula
Devine Formula
Broca Formula
Lorentz Formula
Peterson Formula
Your BMI: – (–)
< 18.5
18.5 – 24.9
25 – 29.9
≥ 30
Healthy Weight Range for Your Height
Based on a BMI between 18.5 and 24.9, your healthy weight range is: –
How to Use This Calculator
Getting started is straightforward. First, select your preferred measurement system – either metric (kilograms and centimetres) or imperial (pounds and feet/inches). Next, choose your sex, as the formulas adjust calculations based on this factor. Enter your height and current weight into the respective fields.
Once you’ve filled in your details, click the calculate button. The calculator will instantly provide your ideal weight according to seven different medical formulas, along with your current BMI and healthy weight range. Each formula offers a slightly different perspective, giving you a comprehensive view of what might be right for you.
Which Result Should You Trust?
The Devine formula is the most widely used in medical practice, particularly for calculating medication dosages. However, no single number defines your perfect weight. Rather than fixating on one result, consider the overall range suggested by multiple formulas. If most results cluster around a similar value, that’s likely a reasonable target for you.
The Science Behind the Formulas
Each formula approaches ideal weight calculation differently, and they were developed at various times using different populations and methodologies.
Devine Formula (1974)
Men: 50.0 kg + 2.3 kg per inch over 5 feet
Women: 45.5 kg + 2.3 kg per inch over 5 feet
Dr B. J. Devine developed this formula primarily for calculating drug dosages. It remains the most clinically validated and is still used by healthcare professionals worldwide. The formula is simple, height-based, and sex-specific.
Robinson Formula (1983)
Men: 52 kg + 1.9 kg per inch over 5 feet
Women: 49 kg + 1.7 kg per inch over 5 feet
This formula modified Devine’s work to better reflect population data from the 1980s. It tends to suggest slightly higher weights for taller individuals.
Miller Formula (1983)
Men: 56.2 kg + 1.41 kg per inch over 5 feet
Women: 53.1 kg + 1.36 kg per inch over 5 feet
Developed around the same time as Robinson’s formula, Miller’s approach provides yet another perspective on ideal body weight, with a different starting point and increment per inch.
Hamwi Formula (1964)
Men: 48.0 kg + 2.7 kg per inch over 5 feet
Women: 45.5 kg + 2.2 kg per inch over 5 feet
One of the earliest formulas, created by Dr G. J. Hamwi for quick calculations. It’s particularly useful for estimating caloric needs and is still referenced in dietetics.
Broca Formula (1871)
Both sexes: Height (cm) – 100
The simplest and oldest formula, developed by French surgeon Paul Broca. Whilst easy to remember and calculate, it doesn’t account for sex differences and may overestimate ideal weight for shorter individuals.
Lorentz Formula (1929)
Men: (Height in cm – 100) – (Height in cm – 150) / 4
Women: (Height in cm – 100) – (Height in cm – 150) / 2
This formula refines Broca’s approach by adding a correction factor that varies by sex. It tends to suggest lower weights than other formulas, particularly for women.
Peterson Formula (2016)
Both sexes: (2.2 × BMI) + (3.5 × BMI × (Height in metres – 1.5))
The most recent addition, this formula uses your target BMI (typically 22) to calculate ideal weight. It’s more flexible and accounts for modern body composition data.
What Your Results Mean
Your results provide multiple perspectives on what constitutes a healthy weight for your height and sex. Here’s how to interpret them and what steps you might consider.
If You’re Below the Healthy Range
Being underweight can affect your energy levels, immune function, and bone health. It may also impact fertility in both men and women. Consider whether you’re eating enough nutrient-dense foods across all food groups. Aim for three balanced meals daily, incorporating healthy fats, proteins, and complex carbohydrates. If you’re struggling to gain weight despite eating well, speak with your GP, as thyroid conditions or other health issues could be contributing factors.
If You’re Within the Healthy Range
Brilliant! Being in the healthy weight range significantly reduces your risk of conditions like heart disease, type 2 diabetes, and certain cancers. To maintain this, focus on a balanced diet rich in fruits, vegetables, whole grains, and lean proteins. Aim for at least 150 minutes of moderate physical activity weekly, including strength training twice a week.
If You’re Above the Healthy Range
Carrying extra weight increases health risks, but small, sustainable changes can make a meaningful difference. Rather than drastic dieting, consider reducing your calorie intake by about 600 calories daily through simple swaps – replace sugary drinks with water, choose whole foods over processed options, and increase your portion of vegetables. A weight loss of 0.5 to 1 kg per week is safe and sustainable. Regular physical activity will help you burn more calories whilst improving your overall health and mood.
Frequently Asked Questions
Each formula was developed using different populations, time periods, and methodologies. Some were designed for clinical drug dosing, others for general health assessment. The variation typically ranges from 2-5 kg, which is normal. Rather than choosing one, consider the overall range as your healthy target zone.
Not entirely. These formulas and BMI calculations don’t account for muscle mass, which is denser than fat. Athletes, bodybuilders, and very active individuals may show as “overweight” despite being healthy. In such cases, body composition analysis (measuring body fat percentage) provides better insight than weight alone.
This calculator isn’t suitable during pregnancy or whilst breastfeeding. Your body’s nutritional needs and appropriate weight change significantly during these periods. Consult your midwife or GP for personalised guidance on healthy weight gain during pregnancy and postpartum recovery.
Slow and steady wins the race. Healthcare professionals recommend losing no more than 0.5-1 kg per week if you need to lose weight. This might feel slow, but it’s the most sustainable approach and more likely to lead to permanent change. Rapid weight loss often results in muscle loss and can be difficult to maintain long-term.
Yes, somewhat. As we age, we naturally lose muscle mass and gain fat, even if our weight stays the same. The formulas here don’t specifically account for age, so older adults might find the results less applicable. Additionally, for people of Black or Asian heritage, the healthy BMI range may be slightly different. Speak with your GP for personalised advice.
No. Children and teenagers aged 2-17 develop at different rates and need age-specific BMI centile charts that compare their measurements to others of the same age and sex. If you’re concerned about a child’s weight, consult their GP or school nurse for appropriate assessment.
If your BMI falls between 18.5 and 24.9, you’re in the healthy range, regardless of what individual formulas suggest. BMI represents a range rather than a single number, which is more realistic since healthy weight varies based on frame size, muscle mass, and other factors. Don’t feel pressured to reach a specific number if you’re already healthy.
Comparing the Seven Formulas
Wondering which formula might be most relevant for you? Here’s a quick comparison to help you decide.
| Formula | Best For | Tends To Suggest | Clinical Use |
|---|---|---|---|
| Devine | General population | Moderate weights | Drug dosing calculations |
| Robinson | Taller individuals | Slightly higher weights | General reference |
| Miller | General population | Moderate weights | General reference |
| Hamwi | Quick estimates | Moderate weights | Nutritional planning |
| Broca | Quick mental maths | Higher weights | Historical reference |
| Lorentz | European populations | Lower weights | Limited clinical use |
| Peterson | Modern populations | Customisable via BMI | Contemporary research |
Beyond the Numbers
Whilst these calculators provide valuable guidance, they’re just one piece of the puzzle. True health encompasses far more than what the scales show.
Consider Your Overall Wellbeing
How do you feel day to day? Can you climb stairs without becoming breathless? Do you have energy for activities you enjoy? Are you sleeping well? These factors matter just as much as the number on the scale. Someone slightly above their “ideal” weight who exercises regularly and eats well may be healthier than someone at their ideal weight who’s sedentary and poorly nourished.
Body Composition Matters
Two people of the same height and weight can look entirely different depending on their muscle-to-fat ratio. Muscle tissue is denser than fat, so someone with more muscle might weigh more but have a leaner appearance and better metabolic health. If you’re exercising regularly, particularly strength training, don’t be discouraged if the scales don’t move as expected – you might be losing fat whilst gaining muscle.
Mental Health Is Health
Obsessing over reaching a specific number can negatively impact your relationship with food and your body. If you find yourself constantly worried about your weight, restricting foods excessively, or feeling guilty after eating, these are signs to seek support. Speak with your GP or contact organisations like Beat Eating Disorders for help.
Remember: This calculator provides estimates based on population averages. Your ideal weight is personal and should be determined in consultation with healthcare professionals who can consider your complete health picture, medical history, and individual circumstances.
References
- National Health Service. BMI healthy weight calculator. NHS Digital, 2024. Available at: www.nhs.uk
- Devine BJ. Gentamicin therapy. Drug Intelligence and Clinical Pharmacy. 1974;8(11):650-655.
- Robinson JD, Lupkiewicz SM, Palenik L, Lopez LM, Ariet M. Determination of ideal body weight for drug dosage calculations. American Journal of Hospital Pharmacy. 1983;40(6):1016-1019.
- Miller DR, Carlson JD, Lloyd BJ, Day BJ. Determining ideal body weight for drug dosage. American Journal of Hospital Pharmacy. 1983;40(6):1622-1625.
- Hamwi GJ. Therapy: Changing dietary concepts. In: Diabetes Mellitus: Diagnosis and Treatment. Vol 1. New York: American Diabetes Association; 1964:73-78.
- Peterson CM, Thomas DM, Blackburn GL, Heymsfield SB. Universal equation for estimating ideal body weight and body weight at any BMI. American Journal of Clinical Nutrition. 2016;103(5):1197-1203.
- World Health Organization. Body mass index – BMI. WHO Regional Office for Europe, 2024. Available at: www.who.int
- National Institute for Health and Care Excellence. Obesity: identification, assessment and management. NICE guideline [CG189]. Published November 2014, updated 2023.
- British Nutrition Foundation. A healthy balanced diet. Updated 2024. Available at: www.nutrition.org.uk
- Bupa UK. BMI Calculator and healthy weight guidance. Reviewed by Niamh Hennessy, Lead Dietitian. Bupa, March 2024.