What these calculators do
A calculator is only useful when you trust what you typed into it, so each of these tools keeps its inputs visible and its result next to them. The BMI calculator takes height and weight and returns a body mass index with its category. The percentage calculator works out a percentage of a number, a percentage change, or what share one number is of another. The EMI calculator turns a loan amount, interest rate and tenure into a monthly instalment. The unit converter switches between length, weight and other everyday units. The random number generator picks numbers in a range you choose.
None of these tools needs an account, and none of them stores your numbers on a Daily Tools server. The calculation happens in your browser, which also means you can re-run a calculation immediately after changing a single input, without reloading or losing your other values.
Choosing the right calculator
Start from the question you are actually answering. If the question is about health, use the BMI calculator, but remember that BMI is a screening measure, not a diagnosis: it does not distinguish muscle from fat, and it is not designed for children in the same way as for adults. If the question is about money, check whether you need a percentage or an instalment: a percentage answers “how much of this?”, while the EMI calculator answers “how much per month?”. If the question is about measurement, the unit converter is the right tool, and it is worth double-checking which unit system your source used before converting.
For anything that affects a real decision — a loan, a medical choice, a purchase — treat the result as a starting point and verify it against the source document or a professional. A calculator removes arithmetic errors, but it cannot check whether the numbers you entered were the right ones.
Common mistakes to avoid
The most common calculator mistake is mixing units: entering height in centimetres into a field that expects metres, or entering an annual interest rate where a monthly rate is expected. Read the unit label next to each field before you type. The second common mistake is rounding too early: keep full precision while you work, and round only the final answer you actually use. The third is trusting a single result without a sanity check — if a monthly instalment looks impossibly low, re-check the tenure and the rate before you believe it.
Tools in this category
- BMI Calculator — Check your Body Mass Index from height and weight.
- Percentage Calculator — Work out percentages, increases and decreases.
- Unit Converter — Convert between everyday length, weight and other units.
- EMI Calculator — Estimate a monthly loan instalment from amount, rate and tenure.
- Random Number Generator Tip Calculator Discount Calculator Compound Interest Calculator Meeting Cost Calculator Subscription Cost Calculator — Pick random numbers in a range you choose.
Frequently asked questions
Are these calculators free to use?
Yes. All ten calculators on this page are free and do not require an account or sign-up.
Do my numbers leave my browser?
The tools are designed to calculate in your browser. Daily Tools is not designed to receive or store the numbers you enter.
Can I use the EMI result to take out a loan?
Use it as an estimate only. A lender's actual instalment depends on its own rates, fees and terms, so confirm the figure with the lender before deciding.
Why does the BMI category matter?
BMI categories are a general guide. They do not account for muscle mass, age, pregnancy or medical conditions, so they should not replace professional health advice.
Related guides
Read the guide to reading your BMI result and the metric to imperial conversion guide on the Daily Tools blog.