What the Chonkometer is actually measuring
Behind the silly needle, the Chonkometer is just calculating Body Mass Index: your weight in kilograms divided by the square of your height in metres. BMI was invented in the 1830s by a Belgian statistician to describe populations, not to read out a verdict on one person standing on a bathroom scale. It says nothing about where your weight sits or what it's made of. A number is not a diagnosis, however confidently our needle points.
How BMI is calculated
BMI is your weight divided by your height squared:
- Metric: BMI = weight (kg) ÷ height (m)²
- Imperial: BMI = 703 × weight (lb) ÷ height (in)²
Example. Someone 1.80 m tall weighing 85 kg: 85 ÷ (1.80 × 1.80) = 85 ÷ 3.24 = 26.2. In imperial, 5'11" is 71 inches, and 187 lb gives 703 × 187 ÷ (71 × 71) = 26.1. The small difference comes from rounding the conversions.
That's the whole recipe. Nothing about fat, muscle, bone or where any of it sits — which is both why BMI is so easy to use and why it's so easy to misread.
BMI chart: what your reading means
The needle uses the World Health Organization categories for adults (WHO, 2000):
| BMI | WHO category | Chonkometer level |
|---|---|---|
| under 18.5 | Underweight | Smol |
| 18.5–24.9 | Healthy weight | Regulation Fluff |
| 25–29.9 | Overweight | A Lil Chonky |
| 30–34.9 | Obesity class I | Chonky |
| 35–39.9 | Obesity class II | Mega Chonk |
| 40 and above | Obesity class III | Off The Dial |
These are the same for men and women. For people of Asian ancestry, health risks tend to rise at a lower BMI, and a WHO expert consultation suggested treating about 23 as the point where risk starts to increase and about 27.5 as high risk (WHO Expert Consultation, 2004). If that's you, read the needle as moving into the next band a little sooner.
Wondering why one number can't tell the whole story? Read why your BMI says little about your health.
Healthy weight for your height
The weights below give a BMI of 18.5 to 24.9 — the WHO healthy range — for each height.
| Height | Healthy weight range |
|---|---|
| 150 cm (4'11") | 41.6–56.0 kg (92–124 lb) |
| 155 cm (5'1") | 44.4–59.8 kg (98–132 lb) |
| 160 cm (5'3") | 47.4–63.7 kg (104–141 lb) |
| 165 cm (5'5") | 50.4–67.8 kg (111–149 lb) |
| 170 cm (5'7") | 53.5–72.0 kg (118–159 lb) |
| 175 cm (5'9") | 56.7–76.3 kg (125–168 lb) |
| 180 cm (5'11") | 59.9–80.7 kg (132–178 lb) |
| 185 cm (6'1") | 63.3–85.2 kg (140–188 lb) |
| 190 cm (6'3") | 66.8–89.9 kg (147–198 lb) |
| 195 cm (6'5") | 70.3–94.7 kg (155–209 lb) |
A range, not a target: where you sit inside it depends on your frame and how much muscle you carry. If you lift, you may sit above it while being perfectly lean — see the next section.
BMI for lifters: the muscle correction
BMI weighs muscle and fat as if they were the same thing. Muscle is roughly 18% denser than fat, so someone who has trained for years can be heavy for their height while carrying little fat. The scale reads that as "overweight", sometimes even "obese".
This isn't a hypothetical. In a 2025 study of 622 male athletes measured with DXA, the standard cut-offs labelled 27.5% of them overweight or obese, while their actual body fat put only about 4% in those categories. The researchers proposed cut-offs of roughly 28 for overweight and 34 for obesity in this group (Milanese et al., 2025).
What the recalibration does. If your BMI is 25 or higher, tick how much you train and the Chonkometer subtracts an offset before choosing your level:
| Training history | Offset |
|---|---|
| No strength training | none |
| 1+ year, 2–3 times a week | 1.5 |
| Long-term, 3+ times a week | 3.5 |
| (Semi-)pro lifter or bodybuilder | 5.5 |
Example. A long-term lifter of 1.80 m (5'11") and 92 kg (203 lb) has a BMI of 28.4: "A Lil Chonky" on the standard scale. With the 3.5 offset, the effective reading is 24.9, which lands in the healthy band.
What it isn't. The offsets are a rule of thumb based on how much extra muscle a training history makes plausible — not a measurement. The research behind them was done on young male athletes, so treat it as a nudge, not a verdict. And above a raw BMI of 35 the Chonkometer stops applying it: at that point only a real body-composition measurement can separate muscle from fat. Want to check? Pinch your skinfolds.
Curious how much denser muscle really is? See does muscle weigh more than fat?
What to use instead if you lift
If you train, treat BMI as a coarse screen and measure your body composition for the real picture. A skinfold measurement with calipers, or a DEXA scan, distinguishes fat from muscle in a way BMI fundamentally cannot. Waist circumference is another cheap, surprisingly useful signal, because it tracks the fat that actually matters metabolically. BMI is the doorbell; body composition is opening the door and looking inside. Your waist-to-height ratio is a good partner here: it ignores muscle on your arms, legs and back and looks only at the middle.
Who BMI works less well for
- Children and teenagers. Under 18, BMI has to be compared with growth charts for age and sex. This calculator is for adults only.
- Older adults. In people over 65, a BMI in the low "overweight" range isn't linked with higher mortality, while risk rises when BMI drops below about 23 (Winter et al., 2014). Losing muscle matters more than a slightly high number.
- Normal BMI, high body fat. Someone with little muscle can sit in the healthy band while carrying too much fat — see skinny fat.
- During pregnancy. BMI isn't meaningful while pregnant; use your pre-pregnancy value and your midwife's or doctor's guidance.
- Very tall or very short people. Squaring the height doesn't scale perfectly, so BMI runs a little high for very tall people and a little low for very short people.
When the number is worth taking seriously
None of this makes BMI useless. At the high end, a genuinely elevated BMI that isn't muscle is a meaningful health flag, and the honest move there is a chat with a doctor rather than a screenshot. The Chonkometer does the jokes; your GP does the medicine.
Frequently asked questions
Is BMI accurate?
What is a healthy BMI?
Why does the Chonkometer let me add for muscle?
Does the Chonkometer store my numbers?
How do I calculate BMI in pounds and inches?
What is a healthy weight for my height?
Is BMI different for men and women?
Does BMI work for children and teenagers?
Is BMI accurate for older adults?
References
Milanese, C., Itani, L., Cavedon, V., et al. (2025). Revising BMI cut-off points for overweight and obesity in male athletes: An analysis based on multivariable model-building. Nutrients, 17(5), 908.
WHO Expert Consultation. (2004). Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. The Lancet, 363(9403), 157–163.
Winter, J. E., MacInnis, R. J., Wattanapenpaiboon, N., & Nowson, C. A. (2014). BMI and all-cause mortality in older adults: A meta-analysis. American Journal of Clinical Nutrition, 99(4), 875–890.
World Health Organization. (2000). Obesity: Preventing and managing the global epidemic. Report of a WHO consultation (WHO Technical Report Series 894). Geneva: WHO.