🩺 Health calculator

Reverse BMI Calculator

Most BMI calculators tell you your BMI from your weight. This one works backwards — enter your height and a target BMI to find the exact weight you need to reach that BMI. See the full healthy weight range, every BMI category threshold for your height, and how much you need to gain or lose from your current weight.

Enter your details

Choose your unit system, enter your height, and pick a target BMI. Your current weight is optional — add it to see exactly how much you need to gain or lose.

🔵 Your height
📏
e.g. 170 for 5 ft 7 in
🟢 Target BMI
🎯
Healthy range: 18.5 – 25.0
⚪ Optional — current weight
⚖️
To see how much to gain/lose

The reverse BMI formula

Standard BMI: BMI = weight (kg) ÷ height² (m)
Rearranged: Weight = BMI × height² (m)
Imperial: Weight (lb) = BMI × height² (in) ÷ 703
Example: BMI 22 at 1.70 m → 22 × 2.89 = 63.6 kg

How this differs from BMI Calculator

The standard BMI calculator asks: "Given my weight and height, what is my BMI?" This tool asks: "Given my height and a target BMI, what weight do I need to reach?" It's the goal-setting version — useful for weight loss or gain planning.

Tip: for most adults, BMI 22–23 is considered the metabolically optimal midpoint of the healthy range (18.5–25). Athletes with high muscle mass may have a higher BMI while remaining lean — in those cases, waist circumference and body fat percentage provide more useful context than BMI alone.
BMI is a population-level screening tool, not a direct measure of body fat or health. It does not account for muscle mass, bone density, age, sex, or ethnic differences in body composition. Always consult a healthcare professional before setting weight goals or beginning a weight management programme.

Frequently asked questions

What is a reverse BMI calculator?

A standard BMI calculator takes your weight and height as inputs and returns your BMI. A reverse BMI calculator takes your height and a target BMI as inputs and returns the weight you need to reach that BMI. It rearranges the BMI formula: Weight = BMI × height² (in metres).

What is the formula for reverse BMI?

Metric: Target weight (kg) = Target BMI × height² (metres). For example, BMI 22 at 170 cm: 22 × (1.70)² = 22 × 2.89 = 63.58 kg. Imperial: Target weight (lb) = Target BMI × height² (inches) ÷ 703.

What BMI should I target?

The WHO defines healthy BMI as 18.5–25. For general health and metabolic function, many clinicians suggest aiming for the midpoint of the healthy range — around BMI 21–23 for most adults. However, the optimal target depends on your age, sex, ethnicity, muscle mass, and medical history. Consult your doctor for personalised guidance.

Is BMI accurate for athletes and muscular people?

Not always. BMI uses total body weight and cannot distinguish between muscle and fat. A highly muscular person may have a BMI in the overweight range while having very low body fat. For athletes, body fat percentage or DEXA scan are more useful measures than BMI alone.

What is the healthy BMI range?

The WHO defines healthy BMI as 18.5 to 24.9. Below 18.5 is underweight, 25.0 to 29.9 is overweight, 30.0 to 34.9 is obesity class I, 35.0 to 39.9 is obesity class II, and 40 or above is obesity class III. Some health organisations use slightly different thresholds for specific population groups.

Related health calculators

BMI Calculator Calculate your current BMI from weight and height — the forward version of this tool. Ideal Weight Calculator Evidence-based ideal weight ranges using multiple formulas (Hamwi, Devine, Robinson, Miller). Calorie Deficit Calculator Once you know your target weight, plan the daily calorie deficit to get there safely. BMR / TDEE Calculator Calculate your base metabolic rate and total daily energy expenditure for weight management.

Disclaimer

This calculator is for educational and planning purposes only. BMI is a population-level screening tool and does not directly measure body fat, health status, or fitness level. It does not account for muscle mass, bone density, age, sex, or ethnic variation in body composition. Always consult a qualified healthcare professional before setting weight goals or beginning any weight management programme.