Ideal Body Weight Calculator (Hamwi Formula)

About the Ideal Body Weight Calculator (Hamwi Formula)

The Hamwi formula is a historical ideal body weight equation that is still reproduced in clinical references. It uses a sex-specific base weight at 5'0" and then adds a fixed increment for each additional inch of height.

Because the formula adds more weight per inch than some later equations, it tends to produce higher estimates for taller people and lower estimates for shorter people. That makes it useful as one reference point, but not a definitive weight target.

When This Page Helps

Hamwi is one of several historical ideal-body-weight equations that may still appear in clinical materials. For taller individuals, it often gives higher estimates than some later formulas, so it is best treated as one reference among several rather than a target to chase.

How to Use the Inputs

1. Select your sex.
2. Enter your height.
3. Optionally enter actual weight for comparison.
4. View your Hamwi IBW with frame-size adjustments.
5. Compare with Devine, Robinson, and Miller formulas.

Example Calculation

Tips & Best Practices

• Hamwi can produce higher estimates for taller people and lower estimates for shorter people than some other formulas.
• The frame-size adjustment (±10%) is a convention used with Hamwi-style estimates. Measure your wrist to estimate frame size.
• For men: small frame = wrist < 6.5", medium = 6.5–7.5", large = > 7.5" (at 5'4"–5'11" height).
• For women: small frame = wrist < 6", medium = 6–6.25", large = > 6.25" (at 5'2"–5'5" height).
• Hamwi is one historical reference equation among several. It is sometimes used because its steeper slope yields higher estimates for taller individuals.

Frame Size Assessment

Wrist circumference is a simple proxy for frame size. Measure at the narrowest point, just distal to the wrist bones, and compare the result with published height-based tables. Frame-size categories used with Hamwi come from historical anthropometric references rather than direct outcome studies.

Hamwi in Historical Context

Hamwi is one of several historical ideal-body-weight equations that were developed before modern body-composition tools were widely available. Newer formulas are often used today, but Hamwi remains a common reference because it is simple and easy to compare against other equations.

Frequently Asked Questions

• Why is Hamwi popular in dietetics?

  Hamwi is commonly reproduced in dietetic references because it is a simple historical equation with an optional frame-size adjustment. Its higher per-inch increment can make it a useful comparison point, but it should not be treated as more accurate than other ideal-body-weight equations.

• How does Hamwi compare to the other formulas?

  Hamwi uses a higher per-inch increment than some later equations, so it can rank lower at shorter heights and higher at taller heights. That crossover behavior is one reason it is best used as a comparison reference, not as a universal standard.

• What is body frame size?

  Body frame size is an anthropometric estimate of skeletal build, usually approximated with wrist circumference or elbow breadth. It is a rough way to contextualize ideal-body-weight formulas, not a direct measure of health.

• Is the Hamwi formula evidence-based?

  Hamwi is a historical formula that is still reproduced in clinical references. It is useful as a comparison point, but it was not built from modern outcome-based validation.

• Should I worry if my weight is above my Hamwi IBW?

  Not necessarily. Being 10–20% above any IBW formula is common and often compatible with good health, especially if you carry more muscle mass than average.

• Can Hamwi be used for children?

  No. Hamwi was designed for adults. Children and adolescents should be assessed with age- and sex-specific growth charts.