How Do You Read a BMI Chart? The Cutoffs, by the Numbers

The only four numbers on the whole chart

Ignore everything else on the chart for a second. There are exactly four numbers that matter, and every chart uses the same ones:

18.5. Below this, you are underweight. 25. From 18.5 up to 24.9 is the healthy range, and 25 to 29.9 is overweight. 30. From 30 up is the obesity range: Class I (30 to 34.9), Class II (35 to 39.9), Class III (40 and above).

That is the entire chart. The colors, the grid, the little body-shape pictures are just a visual wrapper around those numbers. If you are new to BMI, our what-is-my-BMI guide covers the basics of the number itself before you worry about charts.

How to find yourself on the grid

A classic BMI chart is a lookup table. No math needed. Find two positions and read the cell where they cross:

Step 1: Find your height in the leftmost column. Step 2: Find your weight along the top row; use the nearest column if yours is not listed. Step 3: Trace across from your height row and down from your weight column. The cell where they meet holds your BMI number, color-coded by category.

Let's do a real one. Someone 5 feet 9 inches tall weighing 200 pounds: 703 x 200 / (69 x 69) = 29.5. On the chart, the 5'9" row meets the 200 lb column in the overweight color. Or skip the grid and get the exact decimal from a BMI calculator in seconds.

Prefer watching? This short Howcast explainer walks through what BMI means and where it falls short.

The boundary trap nobody mentions

Most charts paint their cells: blue or pale for underweight, green for healthy, yellow for overweight, red for obese. Those colors answer the only question most people have: roughly, where do I stand? But they are zones, not verdicts.

And here is the chart's dirty secret: the boundaries are razor thin, and real measurements are not. A one-inch error in height can flip your category entirely.

I tested this on our own BMI calculator. Same person, 170 pounds. At 5'9" (shoes off): BMI 25.1, overweight. At 5'10" (shoes on): BMI 24.4, healthy. Same body, same morning, different category. One inch of height squared in the denominator moves the number more than most people expect.

My stance is blunt: treating 24.9 and 25.0 as different health states is numerology. The cutoffs are statistical conventions, not biological cliffs. If your number sits near a boundary, ignore the color and watch your trend instead. Weigh yourself under the same conditions a few times, average the readings, and look at whether the number drifts up or down over months. That drift beats any single cell on the chart.

Read the chart backwards: your target weight range

Here is the trick nobody teaches. A BMI chart works in reverse, and that is its most useful direction. Instead of asking "what category am I in," ask "what could I weigh?" Find your height row, then look at the green (healthy) band across it. The weights that band spans are your healthy weight range for that height. No math at all.

Concrete example: at 5'9" (1.75 m), the healthy band runs from BMI 18.5 to 24.9. Times height squared: 18.5 x (1.75 x 1.75) = 56.7 kg, and 24.9 x (1.75 x 1.75) = 76.3 kg. So the range is about 57 to 76 kg, roughly 125 to 168 pounds. The most useful thing the chart gives you, turned into an actual target.

Three people the chart gets wrong

The chart was built for average adults, and it quietly fails for three groups. Athletes and lifters: BMI can't see muscle, so a rugby player at 6 feet and 220 pounds charts as overweight while being visibly fit. Kids and teens: growing bodies don't fit adult cutoffs, so children use BMI-for-age percentile charts that compare them with peers of the same age and sex. Older adults and pregnancy: muscle loss with age can make BMI read healthy while body fat is high, and pregnancy rewrites the rules entirely.

Get your exact number first with HandyNest's free BMI calculator: metric or imperial, instant result, everything in your browser. Then come back to the chart when you want the bigger picture, like your target range.

Frequently asked questions

What BMI is considered healthy?

For adults, 18.5 to 24.9. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 and above is obese.

Is the BMI chart the same for men and women?

Yes. The formula and cutoffs are identical for adult men and women. What differs is interpretation: the same BMI can mean different body-fat levels depending on sex, age, and muscle mass.

Can kids use the same BMI chart?

No. Children and teens use BMI-for-age percentile charts that compare them with peers of the same age and sex.

Why does the chart treat 24.9 and 25.0 as different?

It shouldn't, medically speaking. The boundary is a statistical convention, not a cliff: a tiny measuring error can flip your category, so trends over time matter more than one reading.