Free Online Calculators
A working calculator, the formula behind it, and a worked example — on every page. 20 tools across finance, health, maths, dates and business.
Popular calculators
Calculate profit, margin and markup from a cost and selling price — and see why margin and…
Discount CalculatorWork out the sale price after a percentage discount, how much you save, and what tax adds back…
BMI CalculatorCalculate body mass index from height and weight, and see the healthy weight range for your…
Age CalculatorWork out an exact age in years, months and days from any date of birth, plus the days until…
SIP CalculatorProject what a monthly systematic investment plan could grow to over time, and how much of it…
GST CalculatorAdd GST to a price or strip it out of a GST-inclusive amount, with the CGST and SGST split…
Percentage CalculatorHandle the three percentage questions that come up constantly: what is X% of Y, X is what…
EMI CalculatorWork out the monthly instalment on a home, car or personal loan, and see exactly how much of…
Browse by category
Loans, savings, tax and investment tools for everyday money decisions.
Health & FitnessBody composition and energy estimates based on published clinical equations.
MathsPercentages, averages, ratios and the other arithmetic that comes up constantly.
Date & TimeWork out ages, gaps between dates and how many working days you actually have.
BusinessMargin, markup and return calculations for pricing and planning.
EverydayQuick answers for bills, trips and the small sums of daily life.
Recently added
Work out how much fuel a trip needs and what it will cost, including the cost per…
Tip CalculatorWork out the tip on a bill and split the total evenly between any number of people.
Discount CalculatorWork out the sale price after a percentage discount, how much you save, and what tax adds…
ROI CalculatorMeasure the return on an investment as a total percentage and, where a time period is…
Markup CalculatorApply a markup percentage to a cost to find the selling price, and see the margin that…
Profit Margin CalculatorCalculate profit, margin and markup from a cost and selling price — and see why margin…
About this site
Most calculator sites give you a number and nothing else. This one shows the formula, walks through a worked example and explains what the result actually means, so you can check the working rather than take it on trust.
Every tool runs in your browser, is free to use, and requires no sign-up.
Common questions
Yes. Every calculator on this site is free, requires no account, and has no usage limit.
No. Your inputs are sent to the server to compute the result and are not stored against your identity or used for any other purpose. See the privacy policy for full detail.
Each calculator implements a published, standard formula and is tested against worked examples. Where a method has known limitations — as BMI and calorie equations do — the page says so. For decisions that matter, verify the figure independently and speak to a qualified professional.
Yes. Every page is built mobile-first, results update as you type, and the calculators work on any modern browser.
Because a number you cannot check is a number you cannot trust. Showing the formula and the intermediate steps means you can verify the result by hand if you want to.
Use the contact page and tell us which calculator and which input values produced the problem. We would much rather fix an error than leave it.