BMI Calculator: Check Your Body Mass Index

How to calculate your BMI

Body mass index (BMI) compares your weight with your height:

• Pounds and inches: BMI = 703 × weight (lb) ÷ height (in)²
• Kilograms and meters: BMI = weight (kg) ÷ height (m)²

Example: you’re 5′7″ (67 inches) and weigh 155 lb. That’s 703 × 155 ÷ (67 × 67) = 108,965 ÷ 4,489 = 24.3 – a healthy weight.

The calculator above also shows the healthy weight range for your height and how many pounds you are from it.

BMI chart: what your result means

For adults 18 and over, the CDC and the World Health Organization use these categories:

BMI	Category
below 18.5	Underweight
18.5⁠–⁠24.9	Healthy weight
25⁠–⁠29.9	Overweight
30⁠–⁠34.9	Obesity (class 1)
35⁠–⁠39.9	Obesity (class 2)
40 or more	Severe obesity (class 3)

Healthy weight for your height

This table shows which weight falls into each category at common heights. It applies to women and men alike.

Height	Healthy weight (BMI 18.5–24.9)	Overweight (BMI 25–29.9)	Obesity (BMI 30+)
4′10″	89⁠–⁠119 lb	120–143 lb	144 lb+
5′0″	95⁠–⁠128 lb	129–153 lb	154 lb+
5′2″	102⁠–⁠136 lb	137–164 lb	165 lb+
5′4″	108⁠–⁠145 lb	146–174 lb	175 lb+
5′6″	115⁠–⁠154 lb	155–185 lb	186 lb+
5′8″	122⁠–⁠164 lb	165–197 lb	198 lb+
5′10″	129⁠–⁠174 lb	175–209 lb	210 lb+
6′0″	137⁠–⁠184 lb	185–221 lb	222 lb+
6′2″	145⁠–⁠194 lb	195–233 lb	234 lb+
6′4″	152⁠–⁠205 lb	206–246 lb	247 lb+

BMI for women and men

You don’t need a separate BMI calculator for women or for men: the formula and cut-offs are the same. The difference is body composition – at the same BMI, women have more body fat on average and men more muscle. Men also tend to store extra fat around the belly, which is worse for health. That’s why waist size is worth checking for both (see below).

During pregnancy, BMI isn’t a useful guide. Your BMI from before pregnancy is used to estimate how much weight gain is healthy – talk to your doctor or midwife about it.

BMI by age

• Children and teens (under 18): adult cut-offs don’t apply. Their BMI is compared with growth charts (percentiles) for age and sex, and a pediatrician judges whether a child is underweight or overweight.
• Adults 18 to 64: the categories in the chart above apply.
• 65 and over: an analysis of 32 studies with nearly 200,000 older adults found the lowest risk of death not around a BMI of 20 but closer to 23–24 and a little above. Being overweight wasn’t linked to a higher risk at this age, while a BMI of 20–22 was (Winter et al., 2014). For older adults, unplanned weight loss is often the bigger warning sign.

What research shows about BMI

The largest analysis so far pooled data from more than 10 million adults in 239 studies. Among people who had never smoked and were healthy at the start, the risk of death was lowest at a BMI of 20 to 25. Above that, it rose clearly – by about 30% for every 5 BMI points over 25 (Global BMI Mortality Collaboration, Lancet 2016).

In the US, 40.3% of adults had obesity in 2021–2023, and 9.4% had severe obesity (CDC, NCHS Data Brief 508).

Limits of BMI

BMI is handy because you only need your height and weight. But it has clear blind spots:

• Muscle counts like fat. A muscular athlete can have a BMI over 25 with little body fat.
• It ignores where fat sits. Belly fat is more harmful than fat on the hips and thighs – BMI can’t see the difference.
• Ethnicity matters. People of Asian descent face a higher risk of diabetes and heart disease at a lower BMI. The WHO suggests lower action points for them, starting around 23 (WHO expert consultation, Lancet 2004).

Pair BMI with your waist size. A simple rule: keep your waist to less than half your height – under 33.5 inches if you’re 5′7″. That’s the advice of the UK health body NICE (NICE, 2022), and studies show this ratio predicts heart and diabetes risk a little better than BMI alone (Ashwell et al., 2012).

What to do next

• Healthy BMI: keep your weight steady with balanced eating and regular activity. The calorie calculator shows how much to eat to maintain it.
• BMI over 25: losing just 5–10% of your weight clearly improves blood pressure, blood sugar and blood fats. A moderate calorie deficit of about 300–500 calories a day is the most reliable way to get there. Enough protein helps you keep your muscle.
• BMI under 18.5: ask your doctor to check the cause, especially if you’ve lost weight without trying.
• BMI of 30 or more, or existing health problems: talk to your doctor – effective treatments are available today.

Keep an eye on your weight and BMI. With NutriSmart, you log your weight, see your BMI and hit your calorie goal by snapping a photo of your meal or scanning a barcode.

This calculator is for adults 18 and over. It doesn’t replace medical advice – especially during pregnancy, with an eating disorder or a chronic illness.