A few calculations come up again and again in daily life: checking your body mass index, figuring out an exact age, and converting between measurement units. These three free calculators handle each one in seconds.
Check Your Body Mass Index
BMI (body mass index) is a quick screening number based on your height and weight. You enter your weight and height, and the calculator divides your weight in kilograms by your height in meters squared. The standard ranges are: below 18.5 is underweight, 18.5–24.9 is the healthy range, 25–29.9 is overweight, and 30 or above is obese.
Worked example: Someone weighs 70 kg and is 1.75 m tall. Their BMI is 70 / (1.75 × 1.75) = 70 / 3.0625 ≈ 22.9 — inside the healthy range.
A note of honesty: BMI is a screening tool, not a diagnosis. It does not account for muscle mass, bone density, or body composition. Treat the result as a starting point for a conversation with a health professional, not a verdict.
Find Your Exact Age
An age calculator goes beyond “how old are you in years” — it gives years, months, and days. That precision matters for things like school enrollment cutoffs, insurance forms, and retirement eligibility.
Worked example: Someone born on 5 January 1997 checks their age on 4 October 2026. The result: 29 years, 8 months, and 29 days. No counting on fingers, no off-by-one errors.
Convert Units Quickly
Recipes, travel, and DIY projects constantly mix metric and imperial units. A unit converter turns one system into the other instantly.
Worked example: A weather forecast says it will be 68°F in New York today. Convert to Celsius: (68 − 32) × 5/9 = 20°C — a pleasant spring day, not the heatwave it might sound like. Similarly, a 5-kilometer morning run is about 3.11 miles.
Try it free: BMI Calculator, Age Calculator, and Unit Converter.