Calculate your Body Mass Index, healthy weight range, and target weight. Includes the New BMI formula and reverse BMI. Metric and imperial. Free and instant.
⚕️ Medical disclaimer: BMI is a screening tool, not a medical diagnosis. It does not account for muscle mass, bone density, age, or ethnicity. Always consult a qualified healthcare professional for personalised health advice.
What Weight Do I Need to Be?
Enter your height and a target BMI to find your target weight. Use this to set a realistic, healthy weight goal.
📊 Full Healthy Weight Range
BMI Categories — What Your Number Means
The World Health Organisation (WHO) defines the following BMI categories for adults aged 18 and over. These ranges apply to both men and women.
Below 18.5
Underweight
18.5 – 24.9
Healthy Weight
25.0 – 29.9
Overweight
30.0+
Obese
Obesity is further classified into three classes: Class I (BMI 30–34.9), Class II (BMI 35–39.9), and Class III / severe obesity (BMI 40+). For people of South Asian, East Asian, or Middle Eastern descent, the overweight threshold is lower — a BMI of 23 or above carries increased cardiometabolic risk.
How Is BMI Calculated?
BMI is calculated by dividing your weight in kilograms by the square of your height in metres.
Example: A person who weighs 75kg and is 1.78m tall → BMI = 75 ÷ (1.78²) = 75 ÷ 3.1684 = 23.7 — healthy weight.
BMI Reference Table — Common Heights & Weights
Use this quick-reference table to find the healthy weight range for common heights. All weights shown are the range for a BMI of 18.5 to 24.9. For exact results, use the calculator above.
Height
Underweight (BMI <18.5)
Healthy Weight (BMI 18.5–24.9)
Overweight (BMI 25–29.9)
Obese (BMI 30+)
5'0" / 152cm
Below 43kg (95lb)
43–57kg (95–126lb)
58–68kg (127–150lb)
69kg+ (152lb+)
5'2" / 157cm
Below 46kg (101lb)
46–61kg (101–134lb)
62–74kg (135–163lb)
75kg+ (164lb+)
5'4" / 163cm
Below 49kg (108lb)
49–66kg (108–145lb)
67–79kg (146–175lb)
80kg+ (176lb+)
5'6" / 168cm
Below 52kg (115lb)
52–70kg (115–154lb)
71–84kg (155–186lb)
85kg+ (187lb+)
5'8" / 173cm
Below 55kg (122lb)
55–74kg (122–163lb)
75–89kg (164–197lb)
90kg+ (198lb+)
5'10" / 178cm
Below 59kg (130lb)
59–79kg (130–174lb)
80–95kg (175–209lb)
96kg+ (210lb+)
6'0" / 183cm
Below 62kg (137lb)
62–83kg (137–184lb)
84–100kg (185–220lb)
101kg+ (221lb+)
6'2" / 188cm
Below 65kg (144lb)
65–88kg (144–194lb)
89–106kg (195–233lb)
107kg+ (234lb+)
6'4" / 193cm
Below 69kg (152lb)
69–93kg (152–204lb)
94–112kg (205–247lb)
113kg+ (248lb+)
The New BMI Formula — Is Traditional BMI Flawed?
In 2013, Oxford mathematician Professor Nick Trefethen published a letter in the Economist arguing that the traditional BMI formula has a significant mathematical flaw. His argument: we live in a three-dimensional world, yet BMI uses height squared. This creates a systematic bias that unfairly labels tall people as overweight and short people as underweight.
🔬 The flaw explained: A person who is 10% taller than average but proportionally built should ideally weigh about 10% × 10% × 10% = 33% more. But the standard BMI formula only expects them to weigh 21% more (10% × 10%). This means the formula systematically over-penalises tall people and under-penalises short people.
The Trefethen New BMI Formula
Professor Trefethen proposed replacing height² with height^2.5, splitting the difference between the mathematically correct height³ and the traditional height².
In practical terms, the New BMI formula gives taller people a lower BMI (by about 1 point for a 6-foot person) and shorter people a slightly higher BMI. This affects millions of people's weight classification.
⚠️ Important: As of 2026, no major health organisation — including the WHO, NHS, CDC, or NIH — has officially adopted the Trefethen formula. Standard BMI thresholds remain the global clinical reference. The New BMI is an interesting perspective, not an official medical standard.
Our BMI calculator shows you both results side by side so you can see how the two formulas compare for your height and weight.
BMI Limitations — When BMI Doesn't Tell the Full Story
BMI is a useful population-level screening tool, but it has well-documented limitations for individual health assessment. Here are the most important groups for whom BMI results can be misleading:
💪
Athletes & Muscular People
Muscle weighs significantly more than fat. A muscular athlete can have a BMI of 27-28 — technically "overweight" — while having very low body fat and excellent health. For athletes, body fat percentage is a far more meaningful measurement than BMI.
👴
Older Adults (60+)
Older adults tend to lose muscle mass (sarcopenia) as they age, replacing it with fat. A 70-year-old with a "healthy" BMI of 23 may have significantly more body fat than a 30-year-old with the same BMI. BMI underestimates health risk in older adults.
🌏
Asian & South Asian People
People of South Asian, East Asian, and Middle Eastern descent have a higher risk of type 2 diabetes and cardiovascular disease at lower BMI values. The NHS and WHO recommend lower thresholds: overweight at BMI 23+ (not 25+) for South Asian populations.
🤰
Pregnant Women
BMI is not a useful measure during pregnancy because body composition changes significantly. Weight gain during pregnancy is expected and healthy. Pre-pregnancy BMI is sometimes used for context, but BMI during pregnancy is not clinically relevant.
🧒
Children & Teenagers
Standard adult BMI ranges do not apply to people under 18. For children and teens, BMI-for-age percentiles are used instead (CDC charts), which account for the fact that healthy body composition changes significantly during growth.
📏
Very Tall or Very Short People
As Professor Trefethen's research shows, the standard BMI formula systematically overestimates weight-for-height in very tall people and underestimates it in very short people. The New BMI formula shown in our calculator corrects for this.
Better Alternatives to BMI
For a more complete picture of weight-related health, healthcare professionals increasingly use these measurements alongside BMI:
Waist circumference — A waist of more than 94cm (37 inches) for men or 80cm (31.5 inches) for women indicates increased cardiometabolic risk, regardless of BMI.
Waist-to-height ratio — Divide your waist circumference by your height. A ratio above 0.5 indicates increased health risk. This measure works across different ethnicities and is considered more accurate than BMI alone.
Body fat percentage — Measured via DEXA scan, bioelectrical impedance, or skinfold calipers, body fat percentage directly measures what BMI tries to estimate. Healthy ranges are 14-24% for men and 21-31% for women.
Frequently Asked Questions
What is a healthy BMI?
A healthy BMI for adults is between 18.5 and 24.9 according to the WHO. Below 18.5 is underweight, 25-29.9 is overweight, and 30+ is obese. For South Asian and East Asian people, the overweight threshold is lower at 23+. Use the calculator above to find your BMI and healthy weight range.
What is a healthy BMI for a woman?
The healthy BMI range for women is 18.5 to 24.9 — the same as for men. Women naturally carry a higher percentage of body fat than men at the same BMI value, but the classification ranges are identical. A BMI of 18.5 to 24.9 is considered healthy for adult women of any age.
What is a healthy BMI for a man?
The healthy BMI range for men is 18.5 to 24.9. Men tend to have more muscle mass than women, which can push BMI higher even at a healthy body fat percentage. A muscular man with a BMI of 26 may be healthier than a sedentary man with a BMI of 23. Always consider fitness level alongside BMI.
Is BMI 25 overweight?
Yes — a BMI of exactly 25 is at the boundary of the overweight category (25–29.9). However, this does not necessarily indicate a health problem. BMI is just one screening metric. A muscular person with a BMI of 25 may be in excellent health. Speak to a doctor if you're concerned about your weight and health.
Is BMI 30 obese?
Yes — a BMI of 30 is the threshold for obesity Class I (BMI 30–34.9). Obesity is associated with increased risk of type 2 diabetes, heart disease, and other conditions. However, BMI alone doesn't diagnose health risk. Body fat distribution, waist circumference, fitness level, and other factors all matter. Consult a healthcare professional for a full assessment.
Is BMI accurate for athletes?
No — BMI is not accurate for athletes or very muscular people. Muscle weighs more than fat, so muscular athletes often appear "overweight" on BMI charts despite having low body fat and excellent health. For athletes, body fat percentage, waist-to-height ratio, or DEXA scan results are more meaningful measures.
How much should I weigh for my height?
Use the Target Weight calculator tab above — enter your height and it calculates the weight range for a healthy BMI (18.5–24.9). You can also use the BMI reference table on this page to find the healthy weight range for your height. Remember that "healthy weight" is a range, not a single number.
What is the New BMI formula?
The New BMI formula was proposed by Oxford mathematician Nick Trefethen in 2013. It corrects a flaw in the traditional formula by using height to the power of 2.5 instead of 2: New BMI = 1.3 × weight (kg) ÷ height (m)^2.5. This gives fairer results for tall and short people. However, no major health organisation has officially adopted this formula as of 2026.