Knee Height Calculator (Estimate Height with the Chumlea Equation)
Estimate standing height from knee height with the Chumlea (1985) equations for older adults, for people who cannot stand, plus an estimated BMI from your weight.
How it works
Men: height (cm) = 64.19 − 0.04 × age + 2.02 × knee height (cm) · Women: height (cm) = 84.88 − 0.24 × age + 1.83 × knee height (cm) · BMI = weight ÷ (height in m)²
Knee height — the distance from the sole of the foot to the top of the knee, measured with the ankle and knee at right angles — changes little with age, unlike standing height, which falls with spinal compression and kyphosis. Chumlea, Roche and Steinbaugh (1985) derived these equations in adults aged 60–90 so that height, and therefore BMI, energy needs and drug doses, can be estimated in people who are bedridden, in a wheelchair or cannot stand straight. Measure with a sliding knee-height calliper on the left leg, lying or sitting.
Worked example
A 70-year-old man with a knee height of 52 cm: height = 64.19 − 0.04 × 70 + 2.02 × 52 = 64.19 − 2.8 + 105.04 = 166.4 cm. At 68 kg his estimated BMI is 68 ÷ 1.664² = 24.5, normal weight.
Frequently asked questions
How do I measure knee height?
Have the person lie on their back (or sit) with the knee and ankle both bent at 90°. Place the fixed blade of a knee-height calliper under the heel and the moving blade on top of the thigh just above the kneecap, keep the shaft parallel to the shin and read to 0.1 cm. Average two readings.
Who is this equation for?
It was developed for older white adults aged 60–90 who cannot stand or whose height has shrunk. It is widely used in hospitals and nursing homes for younger adults too, but population-specific equations exist for some ethnic groups and may be more accurate.
How accurate is height from knee height?
The standard error is about 3.5–4 cm, so expect the true height to be within roughly ±7–8 cm for most people. That is accurate enough for BMI screening and energy equations, but not for precise growth tracking.
Why not just ask the person their height?
Older adults often report the height they had when young, which overestimates current height and underestimates BMI. Knee height gives an objective estimate of the person’s full stature.
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This calculator is an educational aid for nutrition and health professionals. It does not replace a clinical assessment — measurement technique strongly affects the result, so interpret it with a qualified professional.