What Is a Healthy BMI? Charts by Age and Sex
Body mass index (BMI) is the quickest way to check whether your weight is in a healthy range for your height. But what exactly counts as a healthy BMI — and does it change depending on your age or sex? The short answer: for adults, a healthy BMI sits between 18.5 and 24.9, the same for men and women at every age. The full answer is a little more interesting, because the number doesn’t tell the whole story.
In this guide, you’ll see the official BMI charts, learn how to calculate your own number, understand what the categories actually mean for men vs women, children vs adults, and older adults — and learn when to trust the number and when to look past it. You can check your own result in seconds with our free BMI calculator.
The Short Answer: Healthy BMI Ranges
For adults aged 20 and over, the World Health Organization (WHO), the U.S. Centers for Disease Control (CDC), and the UK’s NHS all use the same cut-offs:
| BMI range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obese |
These thresholds are identical for men and women, and they don’t shift as you get older. A BMI of 23 means “healthy weight” whether you’re a 25-year-old man or a 55-year-old woman. That said — as we’ll see — your age and sex change how you should interpret the number, even though the number itself comes from the same scale.
How to Calculate Your BMI
The formula is simple:
BMI = weight (kg) ÷ height in metres squared (m²)
For example, a person who weighs 70 kg and is 1.75 m tall:
70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9 — comfortably in the healthy range.
Prefer pounds and inches? The imperial formula is:
BMI = (weight in lbs ÷ height in inches²) × 703
A 150 lb person who is 5’6″ (66 inches): (150 ÷ 4356) × 703 = 24.2 — also healthy, though near the top of the range.
Don’t want to do the maths? Our free BMI calculator handles both metric and imperial in one click and shows your category instantly.
Healthy BMI by Age: Adults vs Children
Here’s where age genuinely matters. For adults (20+), the 18.5–24.9 healthy range applies across the board. For children and teenagers (ages 2–19), it doesn’t — because growing bodies change too fast for fixed numbers.
Kids and teens use percentiles, not cut-offs
A child’s BMI is calculated with the same formula, but the result is compared against growth charts for the child’s exact age and sex and expressed as a percentile. The CDC categories for ages 2–19:
| Percentile | Category |
|---|---|
| Below the 5th | Underweight |
| 5th to below the 85th | Healthy weight |
| 85th to below the 95th | Overweight |
| 95th and above | Obesity |
So a 10-year-old boy with a BMI of 18 might be perfectly healthy (middle of the chart for his age), while the same BMI in an adult woman would be underweight. Children younger than 2 aren’t measured with BMI at all — doctors use weight-for-length charts instead.
What about older adults?
For adults 20 and over, the official categories don’t change with age — but the evidence suggests the optimal zone may shift slightly upward in later life:
- After about age 30, adults lose roughly 3–8% of muscle mass per decade, even if their weight stays stable. The same BMI at 70 often means more body fat than the same BMI at 30.
- Very low BMI in older adults can signal frailty and a higher risk of fractures and falls.
- Some research suggests a BMI of 25–27 may be associated with the lowest mortality risk in adults over 65 — though this is debated, and health bodies still officially use 18.5–24.9.
The practical takeaway: if you’re over 60 and your BMI is in the healthy range, that’s fine. If it sits a little above 25, that alone isn’t necessarily cause for alarm — but it’s worth discussing with your doctor.
Does Sex Change What a Healthy BMI Is?
No — the cut-offs are the same for men and women. But sex changes what the number means in two important ways:
1. Body composition differs. Women naturally carry a higher percentage of body fat than men at the same BMI — roughly 10% more as a rule of thumb. A man and a woman with identical BMIs of 24 can have quite different body-fat percentages.
2. Children’s charts are sex-specific. For ages 2–19, boys and girls follow different growth curves, so the CDC provides separate BMI-for-age charts for each sex.
What BMI Gets Wrong (And When to Ignore It)
BMI was designed in the 1830s as a population-level statistic, not a personal health verdict. It’s a useful quick screen, but it misfires in predictable cases:
- Athletes and muscular people. Muscle weighs more than fat. A rugby player or bodybuilder can land deep in “overweight” territory with very little body fat.
- “Skinny fat.” Someone with a healthy BMI but low muscle mass and high body-fat percentage can face elevated health risk despite a “good” number.
- Very tall or very short people. The formula slightly overestimates for taller people and underestimates for shorter ones.
- Pregnant people. BMI isn’t designed to assess health during pregnancy.
- Certain ethnicities. People of South Asian and Chinese descent tend to develop metabolic risk at lower BMIs; some health bodies apply lower thresholds (around 23 for overweight).
If your BMI falls outside the healthy range but you’re muscular, active, and have a normal waist measurement, talk to a clinician before treating the number as a diagnosis. Strength matters too — bodyweight benchmarks like how long you should be able to plank by age give a useful complementary picture of physical fitness.
Healthy Weight Ranges by Height
For a target BMI of 18.5–24.9, the healthy weight ranges for common heights:
| Height | Healthy weight (kg) | Healthy weight (lbs) |
|---|---|---|
| 5’0″ (152 cm) | 43 – 58 kg | 95 – 128 lbs |
| 5’3″ (160 cm) | 47 – 64 kg | 104 – 141 lbs |
| 5’6″ (168 cm) | 52 – 70 kg | 115 – 154 lbs |
| 5’9″ (175 cm) | 57 – 76 kg | 125 – 168 lbs |
| 6’0″ (183 cm) | 62 – 83 kg | 136 – 184 lbs |
| 6’3″ (191 cm) | 67 – 91 kg | 149 – 200 lbs |
Rather than memorizing the table, plug your numbers into our free BMI calculator to get your personal range instantly.
What to Do With Your Number
BMI is a starting point, not a verdict. Here’s a sensible way to use it:
- Calculate your BMI and find your category.
- Check your waist. A waist measurement above 94 cm (37 in) for men or 80 cm (31.5 in) for women adds meaningful risk information that BMI misses.
- Look at the trend. Weigh yourself weekly, track BMI over months, and react to the trend — not one reading.
- Consider body composition. If the number doesn’t match how you look or feel, a body-fat estimate adds the detail BMI can’t.
- Talk to a clinician before making major changes, especially if your BMI is below 18.5 or above 30.
Health risk rises gradually across the BMI spectrum — someone at 24.9 is barely different from someone at 25.1. The cut-offs are lines drawn on a continuous curve.
FAQ
What is a healthy BMI for a woman?
The same as for a man: 18.5 to 24.9. The WHO, CDC, and NHS use identical thresholds regardless of sex. Women naturally carry a higher body-fat percentage at the same BMI, which is why pairing BMI with a waist measurement is especially useful.
What is a healthy BMI for a man?
18.5 to 24.9. Athletic men with high muscle mass may exceed this range without excess body fat — in that case, waist circumference and body-fat percentage give a more accurate picture.
Does healthy BMI change with age?
For adults 20 and over, the official healthy range (18.5–24.9) doesn’t change with age. However, interpretation shifts: older adults lose muscle and gain fat even at a stable weight, and some research suggests a BMI of 25–27 may carry no extra risk past age 65. For children and teens, BMI is interpreted with age- and sex-specific percentiles, not the adult cut-offs.
Is a BMI of 25 bad?
Not by itself. 25.0 is exactly the line where “healthy” becomes “overweight” — and risk rises gradually, not in a step. Treat it as a prompt to look closer, not a verdict.
What BMI is considered obese?
A BMI of 30 or above is classified as obesity. Health bodies recommend medical guidance at these levels, as risk for heart disease, type 2 diabetes, and other conditions rises significantly.
Why is BMI inaccurate for some people?
BMI can’t tell muscle from fat, so it overestimates risk in athletes and muscular people and can underestimate it in older adults who’ve lost muscle. It also doesn’t capture where fat is stored. Think of BMI as a smoke alarm: good at flagging something worth checking, not at diagnosing the fire.
Conclusion
A healthy BMI for adults is 18.5 to 24.9 — the same for men and women at any adult age. Children and teens are measured differently, with age- and sex-specific percentiles. And while the number is a useful starting screen, it’s not the whole story: muscle mass, fat distribution, and trends over time all matter more than a single reading.
Ready to find out where you stand? Try our free BMI calculator — it takes seconds, works in metric or imperial, and shows your healthy weight range for your height.