About reverse BMI
Reverse BMI calculates a target weight or height from a chosen BMI.
Learn how reverse BMI worksReverse BMI Calculator
Target weight
Enter your values, then calculate to see a verified result.
Reference range
How this result is calculated
A clear calculation path based on your inputs.
Inputs usedReview the information used for this result.
Full calculation and sourcesReview the equation, normalized inputs, assumptions, and version.
Versioned calculationFormula v1.0.0
Adult BMI target ranges
- Below 18.5
- Underweight
- 18.5 - 24.9
- Healthy range
- 25.0 - 29.9
- Overweight
- 30.0 and above
- Obesity range
Important limitation
A reverse BMI result is not an individualized weight recommendation.
View limitationsConvert heightNormalize height to meters
170 cm = 1.70 mSquare your heightHeight (m) × height (m)
1.70 × 1.70 = 2.89Multiply by target BMIBMI × height²
22 × 2.89 = 63.6 kgConvert weightNormalize weight to kilograms
154.3 lb = 70.0 kgDivide by target BMIWeight ÷ BMI
70 ÷ 22 = 3.18Take the square rootSquare root of weight ÷ BMI
√3.18 = 1.784 mInterpretation
The target weight is at the selected BMI.
The selected target is classified as using adult BMI ranges.
Use this estimate as context, not as an individualized treatment goal.
Interpretation
The corresponding height is at the selected BMI.
The selected target is classified as using adult BMI ranges.
Use this estimate as context, not as an individualized treatment goal.
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Method and test recordFormula v1.0.0
- Recorded scope
- health
- Publisher
- CalculatorGeek
- Recorded review date
- 2026-08-30
- Next source review
- 2027-08-30
- Definition fixtures
- 6 configured scenarios
- Published examples
- 6 shown below
Recorded method
No tool-specific review method has been recorded.
These records describe the published model and reference tests. A test-case count is not a certification of every possible input or an independent specialist review. Editorial policy
Known limitations
- Reverse BMI is an algebraic rearrangement of BMI and is a screening aid, not an individualized weight recommendation.
- Adult BMI categories are not interpreted the same way for children and adolescents.
- BMI does not directly measure body fat, muscle mass, fat distribution, pregnancy-related changes, or individual clinical risk.
Method sources
Latest model update
2026-08-30 - Migrated both legacy reverse-BMI modes to the versioned CalculatorGeek engine with conditional validation and metric/imperial equivalence fixtures.
Reference inputs and expected results
Up to 12 examples from the configured definition fixtures are shown. Expected values use the stated output units; invalid inputs are intended to be rejected.
| Case | Inputs | Expected result |
|---|---|---|
| metric target weight | Calculate: target_weight; Height: 170 cm; Target BMI: 22 bmi | Target weight: 63.6 kg; Target weight: 140.2 lb; Healthy-range minimum: 53.5 kg; Healthy-range maximum: 72 kg; classification: healthy |
| imperial target weight equivalence | Calculate: target_weight; Height: 66.9291339 in; Target BMI: 22 bmi | Target weight: 63.6 kg; classification: healthy |
| metric target height | Calculate: target_height; Weight: 70 kg; Target BMI: 22 bmi | Target height: 178.4 cm; Target height: 70.2 in; Healthy-range minimum: 167.7 cm; Healthy-range maximum: 194.5 cm; classification: healthy |
| imperial target height equivalence | Calculate: target_height; Weight: 154.323584 lb; Target BMI: 22 bmi | Target height: 178.4 cm; classification: healthy |
| underweight target boundary | Calculate: target_weight; Height: 2 m; Target BMI: 18.49 bmi | Target weight: 74 kg; classification: underweight (allowed numeric tolerance: 0.1) |
| invalid target BMI | Calculate: target_weight; Height: 170 cm; Target BMI: 5 bmi | Reject invalid input: target_bmi |
Report an issue with this tool. Include the page URL, units, expected answer, and steps to reproduce. Do not include sensitive personal information.
On this page
A reverse BMI calculation finds the weight that corresponds to a chosen body mass index at a known height. It can also solve for the height that corresponds to a known weight and BMI. For example, 170 cm at BMI 22 corresponds to 63.58 kg. This is an algebraic relationship, not a recommendation to reach that weight.
Choose the calculation you need
Select Target weight when height and BMI are known, or Target height when weight and BMI are known. Use the measurement’s unit selector and enter the number in that unit. The result includes the matching measurement and its unit, with additional reference information for the selected mode.
If you already know your measured height and weight and want your current BMI, use the BMI Calculator instead. Reversing the calculation is useful for comparing hypothetical values or checking a worked problem; it does not determine an individual’s healthiest weight.
Reverse BMI formulas
The starting relationship is BMI = weight in kg / height in m2. Rearranging gives:
- Weight (kg) = BMI × height (m)2
- Height (m) = √(weight (kg) / BMI)
Convert measurements before using these formulas manually: divide centimeters by 100 to get meters, multiply inches by 0.0254 to get meters, and multiply pounds by 0.45359237 to get kilograms. The calculator performs the conversion for the selected input unit. BMI must be positive for the reverse-height calculation.
Worked examples
Find weight from 170 cm and BMI 22
- Convert height: 170 / 100 = 1.70 m.
- Square the height: 1.702 = 2.89 m2.
- Multiply by BMI: 22 × 2.89 = 63.58 kg.
The displayed result is approximately 63.6 kg, or 140.2 lb. A display rounded to one decimal place does not change the underlying formula.
Find height from 70 kg and BMI 22
Height = √(70 / 22) = 1.7838 m, approximately 178.4 cm. This answers a mathematical question about the entered numbers. It does not estimate future growth or suggest changing an adult’s height.
Compare BMI reference values at 170 cm
Using the same 2.89 m2 height term, BMI 18.5 corresponds to 53.465 kg and BMI 24.9 corresponds to 71.961 kg. The tool’s reference display rounds these to 53.5-72.0 kg. The exact adult healthy-weight category is BMI 18.5 to less than 25, not an inclusive upper boundary of 24.9. At this height, BMI 25 corresponds to 72.25 kg and is outside that category. Avoid classifying a boundary result from rounded display numbers alone.
Read BMI categories in context
The CDC adult BMI categories apply to adults aged 20 and older: below 18.5 is underweight, 18.5 to less than 25 is healthy weight, 25 to less than 30 is overweight, and 30 or higher is obesity. These are screening categories, not personalized treatment targets.
A value such as BMI 22 is an example input, not a universally ideal BMI. BMI does not directly measure fat, distinguish fat from muscle, or describe fat distribution. The CDC’s BMI FAQ explains why other health information matters. Our Body Fat Calculator offers a separate estimation method with its own assumptions; it also does not replace a clinical assessment.
Unit mistakes to avoid
- 170 cm is 1.70 m. Entering 170 while meters are selected gives a different measurement.
- 5.7 decimal feet is not 5 feet 7 inches. It equals 5 feet 8.4 inches. Use the feet-and-inches fields for a combined measurement, or select inches and enter 67 for 5 feet 7 inches.
- 70 kg is not 70 lb. Check both the input unit and the unit beside the result.
- A category boundary needs unrounded values. Rounding height or weight first can change a result close to a cutoff.
Limits and appropriate use
This tool is for educational calculations using the adult BMI relationship. Children and teens aged 2-19 require age- and sex-specific BMI interpretation, as explained in the CDC FAQ. A reverse-height calculation is not a growth forecast. Do not use a numerical BMI target alone to make medical or nutrition decisions; discuss individual goals and concerns with a qualified health professional.
Keep the input measurements, selected units, chosen BMI, rounding, and these limitations together when recording a result. Explore the Health calculator directory when a different measurement better matches your question.
Sources and method
The examples above are independently worked algebraic calculations. Category and interpretation guidance comes from the CDC’s Adult BMI Categories and BMI Frequently Asked Questions. This page does not claim individual medical review or certify BMI as a diagnosis.