Ideal Body Weight Calculator — IBW by Devine, Robinson & Hamwi Formula

What Is an Ideal Body Weight Calculator?

An ideal body weight calculator estimates the weight considered optimal for your height and sex, using formulas that were originally developed for clinical purposes such as calculating safe medication doses. Unlike a general healthy weight range, which is a broad band derived from BMI, an IBW calculator gives a single reference figure — or, as with our tool, several reference figures from the four most widely cited formulas so you can compare them directly.

The four formulas built into this ideal weight calculator — Devine, Robinson, Miller and Hamwi — were each developed by different researchers between 1964 and 1983, and each uses a slightly different base weight and per-inch adjustment. None of them is definitively "correct"; they are population-derived estimates, and clinicians typically favour the Devine formula because it remains the most extensively validated for drug dosing calculations.

If you are looking for a wider healthy weight band rather than a single figure, our healthy weight range calculator may be more useful. For a UK-specific ideal weight tool with additional guidance, see our ideal weight calculator UK. For your overall BMI and NHS category, use the main BMI Calculator NHS.

How to Use the Ideal Body Weight Calculator

1. Choose metric (cm) or imperial (ft/in) using the unit toggle.
2. Select your sex — all four formulas use sex-specific constants.
3. Enter your height.
4. Optionally enter your current weight to see your adjusted body weight and percentage of ideal weight.
5. Select Calculate My Ideal Body Weight to see results from all four formulas instantly, with no page reload.

The Ideal Body Weight Formulas Explained

Each IBW formula starts from a fixed base weight for exactly 5 feet (60 inches) of height, then adds a set amount for every inch above that. The ideal body weight calculator above applies all four automatically:

Worked Example

Take a male adult who is 175 cm tall. Converting to inches: 175 ÷ 2.54 = 68.9 inches, which is 8.9 inches above 5 feet (60 inches). Applying each formula:

• Devine: 50 + (2.3 × 8.9) = 70.5 kg
• Robinson: 52 + (1.9 × 8.9) = 68.9 kg
• Miller: 56.2 + (1.41 × 8.9) = 68.8 kg
• Hamwi: 48.1 + (2.72 × 8.9) = 72.3 kg

The average across all four formulas is approximately 70.1 kg — illustrating how the four methods typically converge within a 3–4 kg range of each other for the same height.

Ideal Body Weight by Height — Devine Formula Reference Table (2026)

The table below shows approximate ideal body weight using the Devine formula for common UK adult heights. Use it as a quick reference, or enter your exact height and sex in the calculator above for a precise result across all four formulas.

Figures rounded to one decimal place, based on the Devine formula only. For all four formulas at your exact height, use the calculator above.

Interpreting Your Ideal Body Weight Result

• Your current weight is close to your average IBW: this is generally reassuring, though IBW is only one reference point among several.
• Your current weight is noticeably above your IBW: in a clinical context, your adjusted body weight (AdjBW) may be used instead for tasks like medication dosing. For general health guidance, see our NHS weight loss calculator.
• Your current weight is below your IBW: consider whether this reflects a naturally lean build or a genuine underweight concern — our healthy weight range calculator can help clarify this against NHS BMI thresholds.

Common Mistakes When Using an IBW Calculator

• Treating IBW as a strict target: IBW formulas are population averages, not individualised prescriptions — muscle mass, frame size and bone density all vary.
• Confusing IBW with a healthy weight range: IBW gives one figure per formula; a healthy weight range gives a full band based on BMI 18.5–24.9.
• Ignoring formula differences: the four formulas can differ by several kilograms — always check which one a source is using before comparing figures.
• Applying adult formulas to children: IBW formulas are designed for adults; children need NHS growth centile charts instead — see our child growth chart calculator UK.
• Using IBW alone for dosing decisions: clinical dosing typically uses adjusted body weight, and should always be confirmed by a qualified healthcare professional.

Benefits and Limitations of Ideal Body Weight Formulas

Benefits

• Well-established, widely referenced clinical formulas with decades of use
• Useful starting point for medication dosing discussions with healthcare professionals
• Quick to calculate from just height and sex
• Comparing multiple formulas gives a useful sense-check rather than relying on one figure

Limitations

• Does not account for muscle mass, body frame, or bone density
• Originally derived from limited historical population datasets
• Not designed for children, pregnant women, or frail older adults
• Should not be used alone to make medication dosing decisions — always confirm with a pharmacist or doctor

Ideal Body Weight vs Healthy Weight Range: What's the Difference?

Real-Life Example: Using Adjusted Body Weight

Consider a female adult who is 165 cm tall and currently weighs 95 kg. Her average IBW across the four formulas is approximately 59 kg. Because her actual weight is significantly above her IBW, a clinician calculating a medication dose might use her adjusted body weight instead of either figure alone:

This adjusted figure sits between her ideal and actual weight, reflecting that some — but not all — of her additional body mass is metabolically active tissue relevant to dosing. This calculation should always be performed or verified by a healthcare professional rather than used for self-medication decisions.

Expert Tips

• Compare your result against a BMI-based healthy weight range rather than relying on IBW alone
• Use the Devine formula as your primary reference, since it is the most clinically validated
• If your actual weight differs substantially from your IBW, discuss adjusted body weight with your GP or pharmacist before assuming it affects your health
• Track changes over time with our BMI progress tracker or body weight visualizer
• Consider body composition alongside IBW — see our BMI vs body fat percentage guide

Sources & References

• Devine BJ (1974) — Gentamicin therapy. Drug Intelligence and Clinical Pharmacy.
• Robinson JD et al. (1983) — Determination of ideal body weight for drug dosage calculations. American Journal of Hospital Pharmacy.
• Miller DR et al. (1983) — Comparison of methods for estimating ideal body weight.
• Hamwi GJ (1964) — Therapy: changing dietary concepts, in Diabetes Mellitus: Diagnosis and Treatment.
• NHS Live Well — Healthy Weight: nhs.uk/live-well/healthy-weight
• NICE Guideline CG43 — Obesity: Identification, Assessment and Management (2023): nice.org.uk/guidance/cg43

Frequently Asked Questions — Ideal Body Weight Calculator

Conclusion: Finding Your Ideal Body Weight

Your ideal body weight is best understood as a reference point rather than a strict target — the free ideal body weight calculator above gives you results from all four major clinical formulas (Devine, Robinson, Miller and Hamwi) side by side, so you can see how they compare rather than relying on just one figure. As an IBW calculator and ideal weight calculator combined, it also shows your adjusted body weight and percentage of ideal weight if you provide your current weight.

Remember that IBW formulas are population-derived estimates, not individual prescriptions, and were originally designed for clinical dosing rather than general weight-loss goals. For a broader picture of your weight status, pair this tool with our healthy weight range calculator or the main BMI Calculator NHS, and always speak to your GP or pharmacist for personalised medical or dosing advice.