Common mistakes people make with the BMI Calculator
The most common mistake with the BMI Calculator is entering the wrong unit. A height in centimetres where metres are expected, or a rate per month where a rate per year is expected, throws the answer off by a factor of ten or a hundred — and the result still looks like a plausible number, which is what makes the mistake dangerous.
The second mistake is trusting the first answer without a second look. A result that surprises you is worth one more check: re-read each field, confirm the units, and try the calculation again. Most surprises turn out to be a mistyped digit, not a broken calculator.
Worked example, done the wrong way and then the right way: 70 kg at 170 cm: BMI = 70 ÷ 1.70² = 24.22, which sits in the healthy band of 18.5 to 24.9. The wrong way usually involves one of the two mistakes above — a unit slip, or a field left at its default. The right way is the same calculation with the inputs checked.
A habit that prevents most mistakes: write the inputs down before you enter them, then read the calculator’s result lines back against that list. The result lines exist for exactly that check, and using them takes less than a minute.
Frequently asked questions
What is the most common mistake?
Entering the wrong unit, or leaving a field at its default. Both give a result that looks plausible, which is what makes them easy to miss.
How do I check my result?
Read the breakdown lines under the headline number back against the inputs you meant to enter. Then try the calculation once more with round numbers.
What if two calculators give different answers?
Then one of the inputs differs, or the two calculators use different definitions. Compare the inputs field by field before deciding which answer to trust.
More guides on the BMI Calculator
- How to use the BMI Calculator — step by step
- BMI Calculator explained with worked examples
- BMI Calculator formula — how it actually works
- BMI Calculator for beginners — start here
- BMI Calculator vs doing it by hand — which is faster?
- bmi calculator — the complete guide
- How to get an accurate result from the BMI Calculator
- BMI Calculator for students — with examples
- BMI Calculator for homeowners and DIYers
Enter your height and weight to see your BMI and which band it falls in.