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BMI calculator, with its limits

Short answer

Body mass index is weight in kilograms divided by height in metres squared. 70 kg at 175 cm is a BMI of 22.9. For adults, NICE classes 18.5–24.9 as a healthy weight, 25–29.9 as overweight and 30 or more as obesity, with lower thresholds (23 and 27.5) for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background.

Last reviewed 28 October 20262 published sourcesNot medical advice

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BMI calculator

For adults aged 18 and over.

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cm

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BMI categories

NICE classifies adult BMI as: underweight below 18.5, healthy weight 18.5–24.9, overweight 25–29.9, obesity class 1 30–34.9, class 2 35–39.9 and class 3 40 or more (NICE NG246, 2025).

People with a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background tend to develop cardiometabolic risk at a lower BMI, so NICE uses lower thresholds: overweight from 23 and obesity from 27.5, with classes 2 and 3 each 2.5 points lower (NICE NG246, 2025). A WHO expert consultation reached the same 23 and 27.5 cut-off points for Asian populations (WHO Expert Consultation, 2004).

Healthy-weight range by height
HeightBMI 18.5–24.9BMI 18.5–22.9 (lower thresholds)
150 cm (4 ft 11 in)41.6–56.0 kg (92–124 lb)41.6–51.5 kg (92–114 lb)
155 cm (5 ft 1 in)44.4–59.8 kg (98–132 lb)44.4–55.0 kg (98–121 lb)
160 cm (5 ft 3 in)47.4–63.7 kg (104–141 lb)47.4–58.6 kg (104–129 lb)
165 cm (5 ft 5 in)50.4–67.8 kg (111–149 lb)50.4–62.3 kg (111–137 lb)
170 cm (5 ft 7 in)53.5–72.0 kg (118–159 lb)53.5–66.2 kg (118–146 lb)
175 cm (5 ft 9 in)56.7–76.3 kg (125–168 lb)56.7–70.1 kg (125–155 lb)
180 cm (5 ft 11 in)59.9–80.7 kg (132–178 lb)59.9–74.2 kg (132–164 lb)
185 cm (6 ft 1 in)63.3–85.2 kg (140–188 lb)63.3–78.4 kg (140–173 lb)
190 cm (6 ft 3 in)66.8–89.9 kg (147–198 lb)66.8–82.7 kg (147–182 lb)
195 cm (6 ft 5 in)70.3–94.7 kg (155–209 lb)70.3–87.1 kg (155–192 lb)
Weight = BMI × height (m)². Rounded to 0.1 kg and the nearest pound. Example: 70 kg at 175 cm is BMI 22.9.

What BMI misses

BMI is a quick screening number, not a diagnosis. It does not separate muscle from fat or show where fat sits. NICE advises using it with caution in people with high muscle mass and in people aged 65 and over, and recommends measuring waist-to-height ratio as well for adults with a BMI under 35 (NICE NG246, 2025).

Check yours with the waist-to-height ratio calculator. For energy needs at your current weight, try the TDEE calculator.

Focus on the habits behind the number

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Common questions

What is a healthy BMI?

NICE guideline NG246 classes an adult BMI of 18.5–24.9 as a healthy weight. For people with a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, who tend to carry risk at a lower BMI, overweight starts at 23 and obesity at 27.5.

Is BMI accurate for muscular people?

Not very. BMI cannot tell muscle from fat, and NICE advises interpreting it with caution in adults with high muscle mass. Waist-to-height ratio is a better measure of central fat and works for people with high muscle mass.

Does BMI work for older adults or children?

These categories are for adults. NICE advises caution in people aged 65 and over, where a slightly higher BMI may be protective. Children and teenagers need age- and sex-specific BMI centiles instead.

Sources

Figures on this page were checked against these publications on 28 October 2026.

  1. National Institute for Health and Care Excellence. Overweight and obesity management (NG246). Section 1.9: Identifying and assessing overweight, obesity and central adiposity. 2025. www.nice.org.uk/guidance/ng246/chapter/Identifying-and-assessing-overweight-obesity-and-central-adiposity
  2. WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. The Lancet. 2004;363(9403):157–163. doi.org/10.1016/S0140-6736(03)15268-3

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