BMI Calculator
Calculate your Body Mass Index using metric or imperial units. Instant category breakdown — underweight, normal, overweight, or obese.
- Runs in your browser
- Private processing
- No uploads
01Why this BMI tool
BMI with context.
Four reasons people use this page before a physical, a goal-setting session, or a quick reality check.
- 01
Metric and imperial in one place
Kilograms-and-centimeters or pounds-and-feet — pick the units your scale and tape measure use. The formula adapts behind the scenes.
- 02
Category with a visual scale
Underweight, normal, overweight, or obese — your number appears on a color band so the result has context, not just a digit.
- 03
Live recalculation
Drag the weight or height slider and watch your BMI move with it. Great for sense-checking different goal weights.
- 04
Stays on your device
Weight, height, and the result are calculated in your browser. Nothing is stored, sent, or logged.
02How it works
Units, numbers, read.
- UnitsMetricImperial
Step 1Pick units
Toggle between metric (kg, cm) and imperial (lb, ft/in). Switching converts your existing inputs so you don't lose them.
- Your statsHeight175cmWeight72kg
Step 2Enter weight and height
Type or use the sliders. Most adults will pick a single height once and adjust weight as it changes.
- Your BMI23.4kg/m²Normal · 18.5–24.9
Step 3Read your BMI and category
BMI number, your category, and a color-coded scale so you can see how close you are to neighboring bands.
03Use cases
Where BMI fits in.
From doctor's visits to fitness goals to insurance forms — the everyday BMI moments.
Annual health check baseline
Doctors record BMI at most physicals. Calculate yours before the appointment so you go in with context, not surprises.
Pre-visit baselineTrack a fitness goal
Working toward a target weight? Plug in the goal weight to see what BMI it puts you at and whether the category changes.
Goal 75 kg → BMI 24.5Insurance form prep
Some applications and forms ask for BMI. Calculate once, write it down, move on.
Form requirement · BMI 22.1Plan a calorie strategy
Use BMI as a starting frame for whether a cut, recomp, or bulk makes sense. Pair with TDEE for actual calorie numbers.
BMI in 'normal' → recomp focusTrack a child's growth
Children's BMI is interpreted differently (percentile-by-age), but the raw number is still the starting input.
Child BMI · for pediatricianCompare across countries
BMI is the same across countries even though scales aren't. Useful for travelers, expats, and cross-border medical records.
kg/cm ↔ lb/in agreement
04Quick tips
Read BMI honestly.
Four caveats that keep the number useful instead of misleading.
- 01
BMI is a screening tool, not a diagnosis
It works well at the population level but has known blind spots — muscle mass, frame, age, and ethnicity all shift what 'healthy' looks like at any given BMI.
- 02
Pair with body composition
Athletes often score 'overweight' on BMI because muscle is denser than fat. Body-fat percentage paints a more complete picture.
- 03
Categories vary by region
Asia-Pacific guidelines use slightly lower BMI cut-offs for the 'overweight' and 'obese' categories due to body-composition differences. Check local guidance if relevant.
- 04
Trend matters more than the snapshot
A single BMI reading is less useful than a series over months. Track over time to see direction, not just position.
05Loved by
Lifters, office folks, and nurses.
BMI sliders before a recomp. Pair with the body fat calc and I get a realistic picture instead of one misleading number.
Pre-physical sanity check. Beats Googling 'how to calculate BMI' and copy-pasting numbers into a spreadsheet.
Quick reference for adult intake forms across regions. The metric/imperial toggle is the whole reason I open it.
06Questions
BMI, plainly answered.
Common questions before your first calculation. Missing one? hello@wirelogs.com.
01What is BMI?
Body Mass Index — your weight in kilograms divided by your height in meters squared. It's a quick population-level screening number for under-/overweight.
02Which BMI categories does this tool use?
WHO adult cut-offs: underweight (< 18.5), normal (18.5–24.9), overweight (25–29.9), and obese class I–III (30+). Children use percentile-by-age instead.
03Is BMI reliable for athletes?
Not on its own. Muscle is denser than fat, so muscular people often score 'overweight' despite low body fat. Use BMI alongside body-fat percentage for a fuller picture.
04Does my data leave the browser?
No. Calculation is local — weight and height are never sent or stored.
05How often should I check BMI?
Once every few weeks if you're tracking a goal; once a year if you're just monitoring. Daily readings track water weight more than meaningful change.
06Is the tool free?
Yes. No sign-up, no usage cap, no watermark.
Ready when you are
Calculate, contextualize.
Enter your weight and height above. The number and category appear side by side on a color scale.
- Metric · Imperialboth units
- Localprivate
- $0now and always