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Free Ideal Body Weight (IBW) Calculator

This calculator estimates ideal body weight (IBW) from your height and sex using the Devine formula, a simple equation introduced by Dr B. J. Devine in 1974. It is widely used in clinical settings as a quick reference, originally to help with weight-based medication dosing rather than to set a personal weight goal. The result is a rough population-level estimate: it depends only on height and sex and ignores everything that makes real bodies differ, such as muscle, bone structure, frame size, age and body composition. Treat the number as background information, not a target to aim for, and speak with a clinician or registered dietitian for guidance tailored to you.

Ideal body weight (Devine)
70.5 kg

≈ 155.3 lb · Devine formula. A rough population estimate, not a personal target or medical advice — talk to a clinician or dietitian about a healthy weight for you.

Estimate only. This tool is for general information only and is not medical advice or a diagnosis. Results are estimates based on the formula shown. Consult a qualified healthcare professional for guidance about your own situation.

Quick answer

The Devine formula estimates ideal body weight as 50 kg for men or 45.5 kg for women at a height of 5 ft, plus 2.3 kg for each additional inch. For example, a 5 ft 10 in man gives about 73 kg. It is a rough clinical reference, not a personal health target or medical advice.

Formula & method

Men: 50 + 2.3 × (inches over 5 ft)    •    Women: 45.5 + 2.3 × (inches over 5 ft)

Devine formula (result in kg). A rough population estimate — not a personal health target or medical advice.

Examples

Example 1: Man, 5 ft 10 in
Input
Sex: male; height 5 ft 10 in (10 inches over 5 ft)
Result
About 73.0 kg
Why
Starting from the 50 kg base for men at 5 ft, add 2.3 kg per inch: 50 + (2.3 x 10) = 73.0 kg (roughly 161 lb).
Example 2: Woman, 5 ft 5 in
Input
Sex: female; height 5 ft 5 in (5 inches over 5 ft)
Result
About 57.0 kg
Why
Starting from the 45.5 kg base for women at 5 ft, add 2.3 kg per inch: 45.5 + (2.3 x 5) = 57.0 kg (roughly 126 lb).
Example 3: Man, exactly 5 ft 0 in
Input
Sex: male; height 5 ft 0 in (0 inches over 5 ft)
Result
50.0 kg
Why
At exactly 5 ft there is nothing to add, so the estimate equals the base value: 50.0 kg for men (45.5 kg for women). This shows the formula's known weakness at short heights, where it can return implausibly low figures.
Example 4: Woman, 6 ft 0 in
Input
Sex: female; height 6 ft 0 in (12 inches over 5 ft)
Result
About 73.1 kg
Why
Add 2.3 kg per inch above 5 ft: 45.5 + (2.3 x 12) = 73.1 kg (roughly 161 lb). The same per-inch step applies to every height, which is why the estimate is only a linear approximation.

When to use this tool

  • You want a quick, ballpark reference figure for ideal body weight based only on height and sex.
  • You are curious how the Devine formula, commonly seen in clinical and pharmacy settings, produces its number.
  • You need a rough starting point for a conversation with a doctor, nurse or dietitian — not a final answer.
  • You are comparing simple IBW equations (Devine, Hamwi, Robinson, Miller) out of general interest.
  • Do not use it to set diet, training or weight-loss targets, or to make any medical or medication decisions — consult a qualified clinician for those.

Common mistakes

  • Treating IBW as a personal weight goal. The Devine formula was created for clinical estimates (including drug dosing), not as a target you should slim down or bulk up to.
  • Forgetting that the formula only counts inches above 5 ft. A height of 5 ft 4 in uses 4 inches, not 64, in the calculation.
  • Assuming it accounts for build. The formula ignores muscle mass, bone density, frame size and overall body composition, so muscular or large-framed people are often underestimated.
  • Using it at the extremes. It tends to underestimate at short heights (and can give impossibly low values for very short women) and overestimate at very tall heights.
  • Confusing IBW with a healthy weight range. A clinically healthy weight is usually expressed as a range (for example via BMI), not a single number, and varies by individual.
  • Mixing up units. The base values (50 kg / 45.5 kg) and the 2.3 kg-per-inch step are in kilograms and inches; convert carefully if you prefer pounds and centimetres.

Frequently asked questions

Is this calculator medical advice?

No. It provides a general-information estimate using a 1970s clinical formula and is not a substitute for professional advice. For anything related to your health, weight goals, nutrition or medication, please speak with a doctor, nurse or registered dietitian who can assess your full situation.

What is the Devine formula and where does it come from?

It is a simple equation introduced by Dr B. J. Devine in 1974, originally to help estimate weight for medication dosing. It sets a base of 50 kg for men or 45.5 kg for women at a height of 5 ft and adds 2.3 kg for each additional inch of height.

Why does the result not match my actual or healthy weight?

The formula depends only on height and sex, so it cannot reflect muscle, bone structure, frame size, age or body composition. Your real weight and a clinically healthy weight range will often differ from this single estimate, which is normal.

Should I try to reach the weight this calculator shows?

No. The number is a rough population estimate, not a personal target. Healthy weight is usually described as a range that varies by individual. A clinician or dietitian can help you understand what is appropriate for you.

How accurate is the Devine formula?

It is a deliberate simplification. Reviews note it tends to underestimate at short heights — and can give implausibly low values for very short women — and overestimate at very tall heights. It also reflects mainly mid-20th-century Caucasian American data, limiting how widely it applies.

Why do men and women have different base values?

The formula uses a higher starting value for men (50 kg) than for women (45.5 kg) at 5 ft to reflect average differences observed when it was created. This binary, sex-based design is one of its known limitations and does not capture individual variation.

Are there other ideal body weight formulas?

Yes. The Hamwi, Robinson and Miller equations follow a similar height-based approach with different constants, and they can give somewhat different numbers. All share the same core limitation: they ignore body composition and individual build.

Sources & references

External references open in a new tab. We are independent and not affiliated with these organizations.

Disclaimer

This tool is for general information only and is not medical advice or a diagnosis. Results are estimates based on the formula shown. Consult a qualified healthcare professional for guidance about your own situation.

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  • ✓ Runs entirely in your browser — nothing is uploaded.
  • ✓ Formula and method shown above
Last updated: How we calculateReport a correctionDisclaimer

Provided “as is” for general information only — results may be inaccurate, so verify before you rely on them. No warranty; use at your own risk.

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