How to choose the right calculator
Start with the question you are trying to answer, not the tool. "How much will this loan cost me each month?" points to the EMI calculator. "Can I afford this home?" is a different question, answered by the mortgage affordability calculator. If you are not sure, type your question into the search box above. It matches everyday words such as "monthly instalment" or "how old am I", not just calculator names.
Then check the assumptions. Every calculator page explains its formula, what it includes, and what it leaves out. A SIP projection assumes a steady return that real markets never deliver. A due date assumes a regular cycle. Reading those notes takes a minute and tells you how much weight to put on the number.
Getting accurate results
Most calculation errors come from inputs, not formulas. Use the same unit throughout, enter rates as the percentage your bank quotes, and check whether an amount includes tax. Where a calculator offers example values, the result panel says so until you change a field, so you never mistake a sample answer for your own.
For anything with legal, financial or medical consequences, use the result as a starting point and confirm it with the relevant professional or official source. We link to those sources on each page.
What each category covers
Everyday Calculators
Quick tools for the sums that come up every day: splitting a bill, counting days to a deadline, converting a recipe or working out a discount.
Financial Calculators
Plan borrowing, saving and tax with calculators that show their formulas, assumptions and full schedules, so you can check every number.
Health and Fitness Calculators
Estimates based on published formulas, with the method named and the limits explained. Useful for understanding numbers, not for diagnosis.
Education and Scientific Calculators
Maths and science tools that show their working. Built with a safe expression parser, so what you type is calculated, never executed as code.
Construction and Home Calculators
Estimate materials for a project, check what a home or rent fits your budget, and see which appliances drive your electricity bill.
Travel and Utility Calculators
Practical tools for trips and shopping, plus a data storage converter that explains why a 1 TB drive shows less space on your computer.
Security and Sustainability Calculators
A password checker that never sends your password anywhere, and a carbon footprint estimate that shows every emission factor it uses.
Frequently asked questions
Are these calculators really free?
Yes. There is no sign-up, no paywall and no limit on how often you use them.
Do you store the numbers I enter?
No. Calculations run in your browser. The values you type are not sent to our server. The site remembers only which calculators you opened recently and any you mark as favourites, on your own device, and you can clear that list at any time.
How do you check that the results are correct?
Each formula comes from a named, published source listed on its page. Before release, every calculator is run against test cases whose expected answers were worked out independently, including edge cases such as leap years, zero interest rates and invalid input.
Can I use the calculators on my phone?
Yes. Every page works on screens from small phones to large monitors, and every control can be used with a keyboard or screen reader.
I found a mistake. How do I report it?
Please contact us with the page, the values you entered, and the result you expected. We review every report.