Weight & Height Calculator | Free BMI & Ideal Weight Tool
Find out your ideal weight using four medical formulas (Devine, Miller, Hamwi, Robinson), calculate your BMI (Body Mass Index), and check your Waist-to-Height Ratio — a more accurate health risk indicator. Simple, fast, and 100% free.
Why Weight and Height Are the Raw Data for Health
Weight and height are the two most fundamental body measurements. Combined, they unlock a cascade of health information: BMI, ideal weight range, body surface area (important for medication dosing), and — when combined with a waist measurement — the waist-to-height ratio, which some researchers consider a better metabolic risk indicator than BMI.
But here's what most people miss: weight alone is almost meaningless without body composition context. A 200-pound person at 12% body fat and a 200-pound person at 30% body fat have the same BMI but completely different health profiles. This is why our calculator provides multiple metrics — so you get the full picture.
BMI Formula and 8-Tier Classification
Imperial: BMI = (Weight in lbs × 703) ÷ Height² (in inches)
Most sources show only 4 BMI categories. Our calculator uses an 8-tier classification that provides much more nuance:
| BMI Range | Category | Health Risk |
|---|---|---|
| < 16.0 | Severely Underweight | High |
| 16.0 – 16.9 | Moderately Underweight | Moderate |
| 17.0 – 18.4 | Mildly Underweight | Low |
| 18.5 – 24.9 | Normal Range ✅ | Low |
| 25.0 – 29.9 | Overweight | Moderate |
| 30.0 – 34.9 | Obese Class I | High |
| 35.0 – 39.9 | Obese Class II | Very High |
| ≥ 40.0 | Obese Class III | Extremely High |
The Athlete Paradox: When BMI Lies
A 5'11" male athlete weighs 195 pounds with 12% body fat. His BMI is 27.2 — “Overweight” according to the chart. But his actual body fat % is in the athlete range. If he followed BMI-based advice to “lose weight,” he would sacrifice muscle mass and hurt performance.
This is called the athlete paradox, and it affects anyone with above-average muscle mass: bodybuilders, rugby players, CrossFit athletes, powerlifters, and even recreational lifters who have been training consistently for 2+ years.
The fix: If you exercise regularly, use the Body Fat Calculator alongside your BMI. If your body fat % is in the healthy range, your “overweight” BMI is likely muscle, not fat.
Ideal Weight: 4 Medical Formulas, 1 Average
There is no single “ideal” weight for any height. Our calculator averages 4 medically recognized formulas to give you a more reliable range:
| Formula | Year | 5'6" Woman | 5'10" Man |
|---|---|---|---|
| Devine | 1974 | 130 lbs (59 kg) | 166 lbs (75 kg) |
| Miller | 1983 | 130 lbs (59 kg) | 172 lbs (78 kg) |
| Hamwi | 1964 | 126 lbs (57 kg) | 166 lbs (75 kg) |
| Robinson | 1983 | 123 lbs (56 kg) | 161 lbs (73 kg) |
| Average | 127 lbs (58 kg) | 166 lbs (75 kg) |
The calculator then provides a healthy range (±10%) around the average. For the 5'10" man above: 149 – 183 lbs. This gives you a practical target zone rather than a single number.
Originally developed for medication dosing. Most commonly used in hospitals. Men: 50kg + 2.3kg per inch over 5ft. Women: 45.5kg + 2.3kg per inch over 5ft. Typically gives lower estimates.
Updated standard with gentler per-inch increments. Often used in nutritional counseling. Men: 56.2kg + 1.41kg per inch over 5ft. Women: 53.1kg + 1.36kg per inch over 5ft.
Older, stricter formula that tends to give lower ideal weights. Still used in some clinical settings. Men: 48kg + 2.7kg per inch over 5ft. Women: 45.5kg + 2.2kg per inch over 5ft.
Moderate formula that falls between Devine and Miller. Often used as a weight loss goal. Men: 52kg + 1.9kg per inch over 5ft. Women: 49kg + 1.7kg per inch over 5ft.
Waist-to-Height Ratio: The Hidden Risk Indicator
Research increasingly shows that waist-to-height ratio (WHtR) may be a better predictor of cardiovascular risk than BMI. The formula is simple:
Target: Your waist should be less than half your height (WHtR < 0.5). A 40-inch waist on a 5'10" (70-inch) person: 40 ÷ 70 = 0.57 — elevated risk. A 34-inch waist on the same height: 34 ÷ 70 = 0.49 — healthy.
WHtR is especially useful because it accounts for central obesity (belly fat), which is the most dangerous type of fat from a metabolic health perspective. Unlike BMI, WtHR accounts for body fat distribution — abdominal fat (apple-shaped) carries higher health risks than fat stored elsewhere.
Research published in the British Medical Journal found that WtHR is a better predictor of heart disease, diabetes, and stroke than BMI. For example, a person who is 170cm tall should aim for a waist circumference below 85cm (170 × 0.5).
How to Measure Accurately
- Weight: Same time each day (morning, after bathroom, before eating). Use the same scale. Track weekly averages, not daily numbers.
- Height: Barefoot against a wall. Heels together, looking straight ahead. Measure at the top of the head (the crown). Height stops changing after ~age 20.
- Waist: Measure at navel level with abdomen relaxed. Don't suck in. The tape should be snug but not compressing skin.
- Track trends: Weight fluctuates 1-3 pounds daily due to water, sodium, food, and hormones. A 3-month trend is more meaningful than a single weigh-in.
Common Weight Tracking Mistakes
Mistake 1: Relying on BMI Alone
A 200-pound bodybuilder with 12% body fat has a BMI of 27 — “overweight.” If he follows BMI-based advice to lose weight, he'd sacrifice muscle mass and hurt performance. BMI can't distinguish between muscle and fat. Always pair BMI with body fat percentage or waist-to-height ratio.
Mistake 2: Weighing Yourself Daily
Your weight fluctuates 1-3 pounds daily due to water retention, sodium intake, food volume, and hormones. A single weigh-in tells you almost nothing. Track weekly averages instead — take 3 weigh-ins per week (Monday, Wednesday, Friday) and average them. A 4-week trend is far more meaningful than any single number.
Mistake 3: Measuring Waist Incorrectly
Common errors: measuring at the wrong level (should be at navel), sucking in your stomach, or using a tape that's too tight. A 1-inch error in waist measurement changes your WHtR by 0.01-0.02 — enough to cross the 0.5 threshold. Measure at navel level, breathe normally, and keep the tape snug but not compressing.
Mistake 4: Ignoring Body Composition Changes
As you age, you naturally lose muscle mass and gain fat — even if your weight stays the same. A 150-pound person at age 25 with 18% body fat may be 150 pounds at age 45 with 28% body fat. Same weight, very different health profile. Track body fat percentage alongside weight for the full picture.
Limitations of These Measurements
BMI doesn't distinguish between muscle and fat. Athletes and bodybuilders may have a high BMI but very low body fat. Elderly individuals may have lower muscle mass but a normal BMI. Always use alongside other measurements.
The formulas don't account for body frame size, muscle mass, or ethnicity. They provide estimates based on population averages. Your healthy weight may differ. Consult a doctor for personalized advice.
Tips for Healthy Weight Management
- Focus on body composition, not just weight — A healthy weight range with good muscle mass is better than a low weight with low muscle.
- Aim for the healthy BMI range (18.5–24.9) — Use our calculator to find your target range and ideal weight average.
- Track your waist measurement — A WtHR under 0.5 is associated with lower risk of heart disease and type 2 diabetes.
- Make sustainable changes — Aim for 0.5–1kg per week weight change through balanced diet and regular exercise.
- Consider age and gender — Our calculator adjusts ideal weight formulas by gender. As you age, your body composition changes, so regular check-ups matter.
Key Takeaways
- BMI = Weight ÷ Height² — use the 8-tier classification for better nuance
- BMI is misleading for athletes — if you have muscle mass, also check body fat %
- Ideal weight ranges from 4 formulas averaged = more reliable than any single formula
- Waist-to-height ratio should be below 0.5 (waist less than half your height)
- Track weekly, not daily — weight naturally fluctuates day to day
- Use our Weight & Height Calculator for BMI, ideal weight, and body surface area
Frequently Asked Questions
What is BMI and how is it calculated?
BMI (Body Mass Index) = Weight (kg) ÷ Height² (m). For imperial: (Weight in lbs × 703) ÷ Height² (in inches). A BMI of 18.5-24.9 is considered normal. However, BMI doesn't distinguish between muscle and fat, so athletes may have misleading results.
How much should I weigh for my height?
There is no single 'ideal' weight. Most medical professionals use a range of formulas. For a 170cm (5 foot 7 inch) person, the healthy BMI range is 53.5–72.0kg. The average ideal weight from 4 common formulas is approximately 65.5kg for men and 60.5kg for women at that height.
What is the most accurate ideal weight formula?
No single formula is perfect for everyone. The Devine formula is most commonly used in clinical settings for medication dosing. The Miller formula is considered more modern and realistic. We recommend using the average of all four as a practical target.
Is BMI still a good measure of health?
BMI is a useful screening tool but has limitations. It doesn't account for muscle mass, bone density, or fat distribution. Athletes may have high BMI but low body fat. Waist-to-Height Ratio (WtHR) is considered a better predictor of health risks.
Why is BMI not accurate for athletes?
BMI only uses height and weight — it can't tell if your weight comes from muscle or fat. A muscular athlete may have a BMI of 27 ('overweight') while having only 10% body fat. This is called the 'athlete paradox' and is a well-known limitation of BMI.
What is a better metric than BMI?
Body fat percentage is more accurate because it directly measures body composition. Waist-to-height ratio is also useful — your waist circumference should be less than half your height. A 40" waist at 5'10" (70") gives a ratio of 0.57, which is above the 0.5 threshold indicating higher health risk.
What is the Waist-to-Height Ratio and why is it important?
Waist-to-Height Ratio (WtHR) compares your waist circumference to your height. A ratio of 0.5 or less is considered healthy. Research shows WtHR is a better predictor of heart disease, diabetes, and stroke than BMI.
Do men and women have different ideal weights?
Yes. Men generally have higher ideal weights than women at the same height because men have more muscle mass and denser bones. All four formulas used in our calculator have different baselines and per-inch increments for men and women.
How do I measure my waist correctly?
Use a flexible tape measure. Stand up straight and breathe normally. Measure at the narrowest point of your waist, usually just above your belly button. Make sure the tape fits snugly but doesn't compress your skin.
How often should I track my weight and height?
Weigh yourself weekly (not daily — daily fluctuations are misleading). Use the same scale, at the same time of day (morning, after bathroom, before eating). Recalculate BMI and ideal weight when your weight changes by 5+ pounds. Height stops changing after ~age 20.
Weight & Height Calculator Pros & Cons
Pros
- ✅ BMI, ideal weight & WtHR in one tool
- ✅ 4 medical formulas averaged
- ✅ Free forever — no subscriptions
- ✅ Works offline after page load
- ✅ No sign-up or email required
Cons
- ✗ No Excel/CSV export option
- ✗ No dedicated mobile app
Reviewed by Shahid
Content Reviewer & Calculator SpecialistContent reviewer specializing in marketing, finance, health, and math calculators on GM Calculator.