Calculators
These calculators cover the everyday maths that is easy to get wrong by hand: percentage changes, loan repayments, compound interest, body measurements and date arithmetic.
Every calculator on this page states the formula it uses and the assumptions it makes. Where a result depends on a convention that differs between countries — such as how mortgage interest is compounded — the convention is named on the page rather than hidden.
All calculators
- Percentage CalculatorFind a percentage of a number, a share of a total, or a percentage change.
- Discount CalculatorFind the final price and total saving from one or two discounts.
- BMI CalculatorCalculate body mass index and see the healthy weight range for your height.
- Tip CalculatorCalculate a tip, split the bill, and round the total to a clean number.
- Age CalculatorCalculate an exact age in years, months and days from a date of birth.
- Simple Interest CalculatorCalculate interest that is charged only on the original amount.
- Compound Interest CalculatorProject savings growth with any compounding frequency and regular deposits.
- Loan Payment CalculatorWork out loan repayments, total interest and the yearly balance.
- Mortgage CalculatorEstimate monthly mortgage payments, total interest and the yearly balance.
- Percentage Increase & Decrease CalculatorAdd or subtract a percentage from a value, or reverse a change.
- Date Difference CalculatorCount days, weekdays and weeks between any two dates.
- Time Duration CalculatorCalculate hours worked between two times, with breaks deducted.
- Fuel Cost CalculatorEstimate the fuel cost of a journey and split it between travellers.
- ROI CalculatorCalculate return on investment and the annualised growth rate.
- Calorie CalculatorEstimate daily calorie needs and resting metabolic rate.