Math
Percentage Calculator
Calculate a percentage of a number, percentage change, or the original value.
Open calculatorPractical tools, explained clearly
Calculators you can understand, not just use.
Get a quick result, then see the formula, a worked example, and the limits of the estimate. Every calculator runs locally in your browser and requires no account.
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Each tool has its own guide explaining how the calculation works and when the result needs additional context.
Shopping
Discount Calculator
Find a sale price and the amount saved after a percentage discount.
Open calculatorConversions
Unit Converter
Convert common lengths, weights, temperatures, and liquid volumes.
Open calculatorHealth
BMI Calculator
Estimate adult body mass index from metric height and weight.
Open calculatorDates
Age Calculator
Calculate age in years, months, days, and total elapsed days.
Open calculatorFinance
Loan Calculator
Estimate monthly payments, total interest, and total cost for a fixed-rate loan.
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Mortgage Calculator
Estimate principal-and-interest payments for a fixed-rate home loan.
Open calculatorSavings
Compound Interest Calculator
Project savings growth with an initial balance and recurring monthly contributions.
Open calculatorDates
Days Between Dates Calculator
Count the elapsed days and weeks between two calendar dates.
Open calculatorHealth
Calorie Calculator
Estimate basal metabolic rate and daily maintenance calories for adults.
Open calculatorMath
Fraction Calculator
Add, subtract, multiply, divide, and simplify two fractions.
Open calculatorCooking
Cooking Converter
Convert common US volume and weight measures used in recipes.
Open calculatorEducation
GPA Calculator
Calculate a credit-weighted GPA on a 4.0 grade-point scale.
Open calculatorHow these calculators are made
Our calculators use published mathematical formulas and standard conversion factors. Calculations run in your browser, so the values you enter are not sent to our server. We show assumptions and exclusions beside each tool because a useful result should also be understandable.
Financial and health calculators provide educational estimates only. They do not replace advice from a qualified professional who can consider your complete circumstances.