How do you reverse calculate BMI to find weight?

To reverse calculate BMI and find weight, use the formula: Weight (kg) = BMI × Height (m)². For example, for a target BMI of 25 at a height of 170 cm (1.70 m): Weight = 25 × 1.70² = 25 × 2.89 = 72.3 kg. In imperial units: Weight (lbs) = BMI × Height (in)² ÷ 703.

How do you reverse calculate BMI to find height?

To find the height for a given BMI and weight, use: Height (m) = √(Weight (kg) ÷ BMI). For example, for a weight of 80 kg and BMI of 25: Height = √(80 ÷ 25) = √3.2 = 1.789 m (178.9 cm or about 5'10").

What is a reverse BMI calculator used for?

A reverse BMI calculator helps determine the target weight needed to achieve a specific BMI category. Clinicians use it to set weight goals for patients — for example, finding the weight at which a patient's BMI would drop below 30 (obesity threshold) or 25 (overweight threshold). It is also used in surgical planning, medication dosing thresholds, and insurance eligibility assessments.

What weight do I need for a normal BMI?

A normal BMI falls between 18.5 and 24.9 kg/m². The target weight depends on your height. For example, at 170 cm (5'7"): normal weight range is 53.5–72.0 kg (118–159 lbs). At 180 cm (5'11"): 59.9–80.7 kg (132–178 lbs). Use the reverse BMI calculator above to find the exact weight range for your height.

How is reverse BMI different from regular BMI?

Regular BMI calculates your BMI number from your weight and height (BMI = kg/m²). Reverse BMI works backward — you input a target BMI and your height to find the weight you need, or input BMI and weight to find the corresponding height. The underlying formula is the same, just rearranged algebraically.

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Reverse BMI Calculator

Find the target weight for a desired BMI, or find the height that corresponds to a given BMI and weight.

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I want to find:

Target BMI (kg/m²)

Height

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Enter a target BMI and height to find the corresponding weight.

Disclaimer: For educational purposes only. Not a substitute for clinical judgment.

How It Works

The reverse BMI calculation rearranges the standard BMI formula:

Find weight: Weight (kg) = BMI × Height (m)²
Find height: Height (m) = √(Weight (kg) ÷ BMI)

Clinical pearls

Use to set realistic weight-loss targets: find the weight at which a patient's BMI drops below 30 or 25.
Helpful for surgical eligibility — many bariatric surgery criteria require BMI ≥ 40 (or ≥ 35 with comorbidities).
Insurance and medication thresholds often reference specific BMI cutoffs; this tool shows the exact weight needed.
BMI categories may differ for Asian populations (overweight ≥ 23, obese ≥ 27.5 per WHO).

References

World Health Organization. Obesity: preventing and managing the global epidemic. WHO Technical Report Series 894, 2000.
NHLBI Expert Panel. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. Obes Res. 1998;6(Suppl 2):51S–209S.

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About This Tool

What Is a Reverse BMI Calculator?

A reverse BMI calculator works backward from the standard BMI formula. Instead of entering your weight and height to get a BMI number, you enter a target BMI and your height to discover the weight you would need to reach that BMI — or you enter a target BMI and your weight to find the corresponding height. This tool is sometimes called a "BMI reverse calculation" or "reverse calculate BMI" tool.

How to Reverse Calculate BMI for Weight

The standard BMI formula is: BMI = Weight (kg) ÷ Height (m)². To reverse it and solve for weight, simply rearrange: Weight (kg) = BMI × Height (m)². For example, if you want to know what weight corresponds to a BMI of 25 at a height of 175 cm (1.75 m):

Weight = 25 × (1.75)² = 25 × 3.0625 = 76.6 kg (168.9 lbs)

In imperial units: Weight (lbs) = BMI × Height (in)² ÷ 703.

How to Reverse Calculate BMI for Height

To find the height at which a given weight produces a specific BMI: Height (m) = √(Weight (kg) ÷ BMI). For instance, for 90 kg and BMI 30:

Height = √(90 ÷ 30) = √3.0 = 1.732 m (173.2 cm, approximately 5'8")

Clinical Uses of Reverse BMI

Clinicians frequently use reverse BMI calculations in practice, even if they don't always call it by that name:

Weight-loss goal setting: Determine the weight at which a patient crosses from obese to overweight (BMI < 30), or from overweight to normal weight (BMI < 25). This makes abstract BMI categories into tangible weight targets.
Bariatric surgery eligibility: Many insurance policies and clinical guidelines require BMI ≥ 40 (or ≥ 35 with obesity-related comorbidities) for bariatric surgery. The reverse calculator shows patients exactly what weight corresponds to these thresholds.
Medication eligibility: Weight-loss medications like semaglutide (Wegovy), liraglutide (Saxenda), and tirzepatide (Zepbound) have BMI-based prescribing criteria. Reverse BMI helps determine if a patient qualifies.
Insurance assessments: Life insurance and disability assessments often use BMI thresholds. Knowing the exact weight for a given cutoff can be practically useful.

🔑 Clinical Pearls

BMI is a screening tool, not a diagnostic measure. Two patients at the same BMI can have very different body compositions, metabolic profiles, and health risks.
When setting weight targets, consider the "5-10% rule" — even a 5–10% reduction in body weight can significantly improve cardiometabolic risk factors (blood pressure, lipids, HbA1c).
Waist circumference adds prognostic value beyond BMI: >102 cm (men) or >88 cm (women) indicates elevated central obesity risk regardless of BMI.
For Asian populations, use adjusted thresholds: overweight ≥ 23, obese ≥ 27.5 kg/m² (WHO recommendation).

Key References

World Health Organization. Obesity: Preventing and Managing the Global Epidemic. WHO Technical Report Series 894, 2000.
NHLBI Expert Panel. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. Obes Res. 1998;6(Suppl 2):51S–209S.
Jensen MD, Ryan DH, et al. 2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults. Circulation. 2014;129(25 Suppl 2):S102–S138.
WHO Expert Consultation. Appropriate body-mass index for Asian populations. Lancet. 2004;363(9403):157–163.

Formula last verified: February 2026