About our calculators
Some numbers you just need answered quickly and correctly, without opening a spreadsheet or trusting mental math. This category gathers the calculators people reach for most in daily life: working out a percentage or percentage change, finding your exact age down to the day, checking a Body Mass Index in metric or imperial units, estimating a loan’s monthly payment and total interest, calculating a sale price and how much you save, and splitting a restaurant tip across a table. Each one is built to be accurate and to show its working where it helps, so you understand the result rather than just copying a number. They are fast, mobile-friendly and free, and each page includes a short explainer of the formula so the tool doubles as a quick lesson.
Every tool here is free, works on desktop and mobile, and comes with a plain-English guide. Looking for something else? Browse all categories or read our guides.