Calculators

23 free online tools — Finance, health and everyday calculators

Calculators for the decisions and chores of ordinary life: money (loans, mortgages, interest, investment returns, break-even, VAT, tips and discounts), health (BMI, body fat, calories, pregnancy dates, ovulation), school (GPA), travel (fuel cost) and time (age, working days, countdowns, time zones). Each one explains the formula it uses and the assumptions behind it, because a number without its assumptions is a guess with extra confidence.

Car Loan Calculator Payment, interest and the real total cost — with trade-in and sales tax done right. Investment Calculator Work out the return on an investment (total and per year), or the monthly amount needed to hit a savings goal by a date. Body Fat Calculator Height, neck and waist (plus hip for women) → body fat %, fat and lean mass, and where you sit on the ACE chart. Break-Even Calculator Fixed costs, price and cost per unit in; break-even units and revenue, contribution margin and margin of safety out, with a profit table. New Calorie Calculator How many calories you burn a day, and what to eat to lose, hold or gain. Countdown Timer Days, hours, minutes and seconds to any moment, with a shareable link — plus a plain minutes timer that beeps. Discount Calculator What a sale price really is, what you really save — including stacked discounts. Fuel Cost Calculator Distance, your car's consumption and the pump price → fuel needed, total cost and cost per person. GPA Calculator Letter grades and credits in, GPA out — with 4.0 or 4.3 scales, weighted honours courses and your running cumulative. Salary Calculator Convert pay between hourly, daily, weekly, monthly and yearly — on your real working pattern. Tip Calculator Tip, total and each person's share, calculated as you type. Due Date Calculator Due date from your last period, conception date or IVF transfer — plus how far along you are. Ovulation Calculator Enter the first day of your last period and your cycle length to see when you are most likely to ovulate, the six fertile days, and when to test. Retirement Calculator Project your savings to retirement age — in real buying power, not headline numbers. Scientific Calculator Type or tap: trig, logs, powers, roots, factorials and constants, with proper operator precedence. VAT Calculator Net, VAT and gross from either direction, with the standard rates built in. Working Days Calculator Count business days between two dates, or add N working days to a date — with your weekend and your holidays. Percentage Calculator Four calculators in one: percentage of a number, change, and reverse percentages. Mortgage Calculator Estimate your monthly payment including tax and insurance, and see what overpaying saves. Loan Calculator Work out your repayment, total interest and a full payment-by-payment schedule. Compound Interest Calculator Project savings growth with regular contributions and any compounding frequency. BMI Calculator Calculate your BMI in metric or imperial units and see the healthy weight range for your height. Age Calculator Calculate exact age between any two dates, plus totals in months, weeks, days and hours.

Money

The loan and mortgage calculators show the monthly payment and the full amortisation schedule, so you can see how much of each payment is interest. The compound interest calculator projects savings with regular contributions; the investment calculator answers the reverse questions — what did an investment return per year, and how much must I save monthly to hit a goal. For business, the break-even calculator; for everyday sums, percentages, VAT, tips and discounts.

Health

BMI and body fat give you the standard screening numbers with their well-known limits stated; the calorie calculator estimates maintenance calories and refuses to print targets below a safe floor. The due date and ovulation calculators use the same methods a clinic starts from and say plainly that they are estimates, not medical advice.

Dates and time

Exact age in years, months and days; working days between dates with your own holidays; a countdown to any moment; and a time zone converter that gets daylight-saving right because it uses the browser's own zone database.

How to trust a calculator

Check three things: that it shows its formula, that it lets you change every assumption (rate, period, rounding), and that it handles the edge cases honestly — a 0% loan, a negative margin, a cycle that is not 28 days. Every calculator here is built to pass that test, and the tests that verify them are part of the site.