Ideal Weight Calculator
Find your ideal weight using proven medical formulas
Use the ideal weight calculator above to find your ideal body weight using proven medical formulas. Simply choose Metric (Cm & Kg) or Imperial (Ft, In & Lbs), select your gender, enter your height (and optionally your age and current weight) — the tool instantly delivers your ideal weight from five clinically used formulas (Devine, Robinson, Miller, Hamwi, and BMI‑based), your healthy weight range, and your current BMI category. Whether you are tracking fitness goals, planning a weight loss programme, or simply curious how your weight compares to medical standards, this free online ideal weight calculator provides accurate, evidence‑based results in seconds.
Below you will find a complete step‑by‑step guide to using the ideal weight calculator, detailed explanations of each formula, worked examples in both metric and imperial units, a healthy weight range reference, and answers to common questions about ideal weight and BMI.
How to Use the Ideal Weight Calculator
The ideal weight calculator is designed for fast, accurate results in either measurement system. Follow these simple steps:
- Select Unit System: Choose Metric (Cm & Kg) if you prefer centimetres and kilograms, or Imperial (Ft, In & Lbs) for feet, inches, and pounds. The calculator automatically converts and displays results in your chosen system.
- Choose Gender: Tap Male or Female. Ideal weight formulas use slightly different constants for each gender because of average body composition and frame differences.
- Enter Your Height: In Metric, enter height in centimetres (e.g., 165 cm). In Imperial, enter feet and inches separately (e.g., 5 ft 9 in). Height is the most important input because all five formulas derive ideal weight from height above 5 feet (152 cm).
- Enter Age (Optional): Age improves the accuracy of certain calculations and provides additional context for the result.
- Enter Current Weight (Optional — for BMI): Adding your current weight unlocks an automatic BMI calculation with a coloured category indicator (Underweight, Normal, Overweight, Obese). Skip this if you only want the ideal weight number.
- Click “Calculate Ideal Weight” — The ideal weight calculator instantly displays your ideal weight (Devine formula by default), a healthy weight range, a six‑card formula breakdown (Devine, Robinson, Miller, Hamwi, BMI‑Based, Average), your BMI value with category, and a guidance note if you are above or below your ideal range.
- Click “Reset Calculator” to clear all fields and start a new calculation.
Understanding the Five Formulas
The ideal weight calculator uses five widely accepted medical formulas. Each was developed in a different era for slightly different clinical purposes:
1. Devine Formula (1974)
Women: IBW = 45.5 kg + 2.3 × (inches over 5 ft)
The most widely used formula in clinical medicine, especially for drug dosage calculations. Originally developed by Dr. B. J. Devine. Read more on Wikipedia’s body weight overview.
2. Robinson Formula (1983 Revised)
Women: IBW = 49 kg + 1.7 × (inches over 5 ft)
A modernised revision of the Devine equation, slightly more conservative for taller individuals. Often used in nutritional research.
3. Miller Formula (1983)
Women: IBW = 53.1 kg + 1.36 × (inches over 5 ft)
Developed for studies on lean body mass; tends to produce slightly higher targets, particularly useful for athletes with muscular builds.
4. Hamwi Formula (1964)
Women: IBW = 45.5 kg + 2.2 × (inches over 5 ft)
The oldest formula still in active clinical use, developed by Dr. G. J. Hamwi for diabetes management. Considered a clinical standard for nutritional planning.
5. BMI‑Based (Target BMI 21.5)
Uses a target BMI of 21.5 (the midpoint of the healthy BMI range 18.5–24.9) to calculate ideal weight. Aligned with WHO health guidelines. Learn more on the World Health Organization’s obesity page.
Worked Example — Metric (Male, 165 cm)
Using a 165 cm male as a working example:
- Inches over 5 ft = (165 − 152.4) / 2.54 ≈ 5 inches
- Devine: 50 + (2.3 × 5) = 61.4 kg
- Robinson: 52 + (1.9 × 5) = 61.4 kg
- Miller: 56.2 + (1.41 × 5) = 63.2 kg
- Hamwi: 48 + (2.7 × 5) = 61.4 kg
- BMI‑Based (21.5): 21.5 × (1.65)² = 58.5 kg
- Average of all five: ~61.2 kg
- Healthy Weight Range: 50.4 kg – 67.8 kg
Devine
61.4 kg
Robinson
61.4 kg
Miller
63.2 kg
Hamwi
61.4 kg
BMI‑Based
58.5 kg
Average
61.2 kg
Worked Example — Imperial (Male, 5 ft 9 in)
For a male 5 ft 9 in tall (≈175 cm), inches over 5 ft = 9:
- Devine: 50 + (2.3 × 9) = 70.7 kg ≈ 155.9 lbs
- Robinson: 52 + (1.9 × 9) = 69.1 kg ≈ 152.3 lbs
- Miller: 56.2 + (1.41 × 9) = 68.9 kg ≈ 151.9 lbs
- Hamwi: 48 + (2.7 × 9) = 72.3 kg ≈ 159.4 lbs
- BMI‑Based: 21.5 × (1.75)² = 65.8 kg ≈ 145.6 lbs
- Average: ~153.0 lbs
- Healthy Range: 125.3 lbs – 168.6 lbs
BMI Reference Chart
If you enter your current weight, the ideal weight calculator automatically computes your Body Mass Index (BMI) and categorises it. Use this table for context:
| BMI | Category | Health Indication |
|---|---|---|
| < 18.5 | 🟦 Underweight | Possible nutritional deficiency — consult a doctor |
| 18.5 – 24.9 | 🟩 Normal | Healthy weight range for most adults |
| 25.0 – 29.9 | 🟧 Overweight | Increased health risks; consider lifestyle changes |
| ≥ 30.0 | 🟥 Obese | High health risk; medical guidance recommended |
BMI categories follow the CDC’s adult BMI guidelines. For a more detailed BMI assessment, try our dedicated BMI Calculator.
Why Ideal Weight Matters for Your Health
Maintaining a healthy weight reduces the risk of multiple chronic conditions:
- Cardiovascular health — Lower risk of heart disease, hypertension, and stroke. Read the American Heart Association’s weight management guidance.
- Diabetes prevention — Healthy weight significantly cuts the risk of type 2 diabetes.
- Joint and bone health — Less mechanical stress on knees, hips, and lower back.
- Energy and mental clarity — Easier daily movement and improved mood.
- Better sleep quality — Reduced risk of sleep apnea and insomnia.
Limitations of Ideal Weight Formulas
While these formulas have stood the test of time, they were developed decades ago using limited population data. Keep these caveats in mind:
- No body composition data — Formulas can’t distinguish muscle, fat, or bone density.
- Frame size variations — Small or large‑framed individuals may need adjustments.
- Ethnic differences — Asian populations often have higher health risk at lower BMIs, while Pacific Islander populations may be healthy at higher BMIs.
- Age‑related changes — Older adults naturally lose muscle (sarcopenia), so the “ideal” shifts with age.
- Pregnancy — These formulas do not apply during pregnancy.
Frequently Asked Questions
What is an ideal weight calculator?
An ideal weight calculator is a free online tool that estimates your healthy target weight using clinically validated medical formulas — Devine, Robinson, Miller, Hamwi, and BMI‑based. You enter your gender and height (and optionally age and current weight) to get an instant result along with your healthy weight range and BMI.
Which ideal weight formula is most accurate?
No single formula is “best” for everyone. The Devine formula is most widely used in clinical medicine, while the BMI‑based calculation aligns with WHO health guidelines. The Average card combines all five formulas for a balanced, realistic target.
Why are men and women given different ideal weights?
On average, men have higher muscle mass and bone density, while women carry slightly more essential body fat. All ideal weight formulas use gender‑specific constants to reflect these biological differences.
Is ideal weight the same as healthy weight?
Not exactly. Ideal weight is a single target number, while healthy weight is a range (typically defined by a BMI of 18.5–24.9). Many weights within the healthy range can support good health.
Should athletes use this calculator?
Athletes and very muscular individuals often weigh more than the calculator suggests because muscle is denser than fat. They should also use a body fat percentage measurement (DEXA, skinfold calipers, or BIA) for a more accurate assessment.
Does the calculator save my data?
No. All calculations happen locally in your browser. Your height, weight, age, and gender are never stored, shared, or sent to a server.
Can I use this calculator during pregnancy?
No. Ideal weight formulas do not apply during pregnancy. Consult your healthcare provider for pregnancy‑specific weight gain recommendations.
How often should I check my ideal weight?
Your ideal weight depends on height (which doesn’t change in adults) and gender, so the number stays the same. However, you should regularly track your current weight and BMI to monitor progress toward — or away from — that target.
External Resources
- Adult BMI – CDC — Official Centers for Disease Control guidance on BMI calculation, categories, and health implications.
- Obesity and Overweight – WHO — World Health Organization’s global guidance on healthy weight and obesity prevention.
- Assessing Your Weight and Health Risk – NHLBI — National Heart, Lung, and Blood Institute tool for evaluating weight‑related health risks.
- Human Body Weight – Wikipedia — Comprehensive overview of ideal weight formulas, their history, and modern alternatives.
- Losing Weight – American Heart Association — Practical, evidence‑based guidance on achieving and maintaining a healthy weight.