Calculators that show their math
Free, quick and private. Every result comes with the formula behind it, so you can check the answer instead of trusting it.
Loans & debt
Loan CalculatorMonthly payment, total interest and a year-by-year balance for any fixed-rate loan.Mortgage CalculatorFull monthly housing payment with property tax, insurance, PMI and HOA.Auto Loan CalculatorCar payment with down payment, trade-in, sales tax and fees.Credit Card Payoff CalculatorHow long it takes to clear a balance and how much interest you will pay.Amortization CalculatorFull monthly payment schedule with extra payments and interest saved.Refinance CalculatorMonthly savings, break-even point and lifetime cost of refinancing a loan.
Savings & income
Compound Interest CalculatorProject savings or investment growth with monthly contributions.Savings Goal CalculatorHow much to save each month to reach a target amount by a set date.Retirement CalculatorProject your retirement savings, in future and in today's dollars.Hourly to Salary CalculatorConvert hourly pay to annual, monthly, weekly and biweekly pay, and back.50/30/20 Budget CalculatorSplit your after-tax income into needs, wants and savings.Simple Interest CalculatorInterest and total amount using I = P × r × t, compared with compound interest.APY Calculator (APR to APY)Convert APR to APY, or APY to APR, and see a year of interest on a deposit.
Everyday math
Profit Margin CalculatorMargin, markup and profit from cost and price, plus the price for a target margin.Percentage CalculatorPercent of a number, what percent one number is of another, and percent change.Tip CalculatorWork out the tip and split the bill between any number of people.Sales Tax CalculatorAdd sales tax to a price, or remove it from a total. Works for VAT and GST too.Discount CalculatorSale price and savings after a percentage discount, including stacked discounts.Percentage Change CalculatorPercent increase or decrease between two numbers, plus percentage difference.
Date & time
Age CalculatorExact age in years, months and days, plus your next birthday.Days Between Dates CalculatorCount the days, weeks, months and weekdays between two dates.Add or Subtract Days from a DateFind the date that is a number of days, weeks, months or years from any date.Weeks From Date CalculatorFind the date any number of weeks from a date, or the weeks between two dates.
Health
Unit converters
Length ConverterConvert mm, cm, m, km, inches, feet, yards and miles.Weight ConverterConvert kg, grams, pounds, ounces, stone and tonnes.Temperature ConverterConvert Celsius, Fahrenheit and Kelvin with formulas and a reference chart.Height Converter (cm to Feet & Inches)Convert centimeters to feet and inches, or feet and inches to centimeters.
Text & security
Guides
Monthly payment formula: how to calculate a loan installmentThe formula, what each letter means, and a worked installment example.How compound interest worksWhy interest on interest is so powerful, with clear examples.Percent change formula: how to calculate percentage increase or decreaseThe formula, worked examples for increase, decrease and year-over-year, and common mistakes.How much house can I afford? The 28/36 ruleA simple income-based method for setting a home budget.How to pay off credit card debt fasterAvalanche versus snowball, with real numbers and a step-by-step plan.How much car can I afford? The 20/4/10 ruleA simple rule for keeping car costs in proportion to your income.The 4% rule: how much do you need to retire?What the 4% rule says, how to use it, and its limits.The 50/30/20 budget rule explainedA simple way to split your income between needs, wants and savings.Profit margin vs markup: what's the difference?Why margin and markup differ, and how to price for the profit you want.BMR and TDEE explainedWhat BMR and TDEE mean and how to use your calorie estimate sensibly.APR vs APY: what's the difference?Why APY is higher than APR, and which one to compare.How loan amortization worksHow each payment splits into interest and principal, and what extra payments do.Should I refinance my mortgage?The break-even test, the term trap and a checklist before you switch.
No calculators match that search. Try a shorter word, such as "loan" or "date".
Everything on CalcEmperor runs in your browser, so the numbers you type stay on your device. Each tool page includes the formula, a worked example and answers to common questions. Results are estimates for planning and education, not professional advice.