Free online calculators
Work out a mortgage payment, a percentage, your BMI or the days between two dates. Every calculator shows its formula and the working behind the answer.
Browse by category
Financial calculators
- Mortgage Calculator
- Home Affordability Calculator
- Refinance Calculator
- Loan Calculator
- Auto Loan Calculator
- Credit Card Payoff Calculator
Math calculators
- Scientific Calculator
- Percentage Calculator
- Fraction Calculator
- Ratio Calculator
- Average Calculator
- Standard Deviation Calculator
Health and fitness calculators
- BMI Calculator
- Calorie Calculator
- BMR Calculator
- Body Fat Calculator
- Ideal Weight Calculator
- Macro Calculator
Worth a closer look
- Mortgage CalculatorMonthly payment with taxes, insurance and PMI, plus total interest and payoff date.
- Compound Interest CalculatorBalance, interest and APY for any compounding frequency, with optional regular deposits.
- Scientific CalculatorAn on-screen scientific calculator with trigonometry, logarithms, powers and a step-by-step working.
- Percentage CalculatorPercent of a number, percentage change, reverse percentages and increases, with the working.
- BMI CalculatorBody mass index from height and weight, with your weight class and healthy range.
- Calorie CalculatorDaily calories to maintain your weight, plus targets for losing or gaining at three steady paces.
- Age CalculatorExact age in years, months and days, with totals in weeks, days and hours and the next birthday.
Guides
- How mortgage payments are calculatedThe amortization formula explained from first principles, with a month-by-month example and the effect of rate, term and extra payments.
- Compound interest explainedInterest on interest, step by step: the formula, the effect of compounding frequency, the Rule of 72 and regular contributions.
- How to calculate percentagesPercent of a number, what percent one number is of another, percentage change and working backwards — with the traps that catch people out.
- What BMI tells you — and what it doesn’tThe history of BMI, why it is a screening number rather than a diagnosis, and how waist measurements add what it misses.
How Qalkulator works
The working, not just the answer
Results come with the formula and each step filled in with your numbers, so you can check the math or reuse it.
Built for the phone in your hand
Large inputs, instant results as you type and tables that stay readable on a small screen.
Nothing to install, nothing stored
Calculations run in your browser. What you type is not sent to a server or saved.