A reverse BMI calculator works backwards from the standard BMI formula. Instead of calculating BMI from your height and weight, it takes your height and a target BMI and calculates the weight you would need to be to achieve that BMI. This is useful for setting realistic weight goals based on a specific BMI target.

The standard BMI formula is: BMI = weight(kg) ÷ height(m)². Rearranging for weight gives: Weight(kg) = BMI × height(m)². In imperial units: Weight(lb) = BMI × height(inches)² ÷ 703. This calculator performs that calculation instantly for any target BMI you choose.

According to the World Health Organization (WHO), a BMI between 18.5 and 24.9 is considered a healthy weight for most adults. A BMI below 18.5 is classed as underweight, 25.0–29.9 is overweight, and 30.0 or above is classified as obese. These thresholds may differ slightly for certain ethnic groups.

BMI is a simple, widely used screening tool but has limitations. It does not measure body fat directly and cannot distinguish between muscle and fat. Athletes may have a high BMI due to muscle mass without excess body fat, while some individuals with a ‘normal’ BMI may still have unhealthy levels of body fat. BMI should be used alongside other assessments such as waist circumference, blood pressure, and cholesterol levels for a complete picture of health.

Yes. Enter your current height and set your target BMI (e.g. 22 for a mid-healthy-range goal). The calculator will tell you the weight you need to reach that BMI, and — if you also enter your current weight — how much you need to lose or gain. Always consult a healthcare professional before starting any weight loss or gain programme.

BMI is a ratio of weight to height squared and applies to any target weight range. Ideal body weight (IBW) formulas (such as Devine or Robinson) produce a single number based on height and sex, often without reference to a BMI category. Reverse BMI is more flexible: you choose which BMI you are targeting, so the resulting weight is not a fixed ‘ideal’ but the weight that would put you at your chosen BMI.

Standard adult BMI categories do not apply to children and teenagers. Children’s BMI is interpreted using age- and sex-specific percentile charts (BMI-for-age). This reverse BMI calculator is designed for adults aged 18 and over. For children, consult a paediatrician or use age-appropriate growth chart tools.

To calculate manually in metric: Target weight (kg) = Target BMI × height (m)². Example: for a target BMI of 22 and a height of 1.70 m → 22 × (1.70)² = 22 × 2.89 = 63.58 kg. In imperial: Target weight (lb) = Target BMI × height (inches)² ÷ 703. Example: BMI 22, height 67 inches → 22 × 4489 ÷ 703 ≈ 140.4 lb.