PercentageCalculatorHub

Calculators that show their working

Every tool comes with the formula, a worked example and the source it was checked against. Nothing you type leaves your browser.

Percentage Calculator

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Enter your numbers to see the result.

Full percentage calculator, with the formula and worked examples

Calculators

Free, no sign-up, metric and imperial where it matters.

Percentages

Percentage CalculatorThree calculators in one: find a percentage of a number, work out what percentage one number is of another, and measure percentage increase or decrease between two values.Percentage Difference & Percent Error CalculatorCompare two numbers with the percentage difference formula, or measure percent error against a known true value.Reverse Percentage CalculatorWork backwards from a final figure to the original value before a percentage was added or taken off.Discount CalculatorFind the sale price and saving, stack two discounts the way shops actually apply them, or work out what percentage off a price really is.Margin & Markup CalculatorGet gross margin, markup and profit from cost and price, or work out the selling price that hits a target margin.GST CalculatorAdd GST to a price or take it out of an inclusive one, with the CGST and SGST split for intra-state sales.

Students and grades

GPA CalculatorEnter your courses, letter grades and credits to get your semester and cumulative GPA on a 4.0 scale.Grade CalculatorAdd each assignment with its score and weight to see your current grade, then find out what you need on the final.Marks Percentage CalculatorEnter the marks you scored and the maximum for each subject to get your total and overall percentage.CGPA to Percentage CalculatorConvert a CGPA to a percentage, or a percentage to CGPA, using the rule your board or university actually applies.Attendance CalculatorFind your attendance percentage and how many classes you need to attend, or can afford to miss, to stay above the requirement.

Money and pay

Compound Interest CalculatorSee how a balance grows with compound interest and regular contributions, year by year.Loan & Mortgage CalculatorWork out the monthly payment on any amortising loan, along with the total interest you will pay over its life.CAGR CalculatorWork out the compound annual growth rate between two values, or project a value forward at a steady rate.Salary CalculatorConvert pay between hourly, daily, weekly, monthly and annual figures, with control over hours per week and paid weeks per year.Salary Hike CalculatorFind the percentage hike between two salaries, or your new salary after a raise.Tip CalculatorEnter the bill, pick a tip percentage, and split the total across your party.

Health

BMI CalculatorCalculate body mass index from height and weight in either metric or imperial units, and see which category the result falls into.TDEE CalculatorEstimate the calories you burn in a day, from your basal metabolic rate up through your activity level.

Everyday tools

Unit ConverterConvert length, weight, temperature, volume, area and speed between metric, imperial and US units.Word CounterCount words, characters, sentences and paragraphs, with reading and speaking time. Your text stays on your device.Age CalculatorEnter a date of birth to get an exact age broken down into years, months and days, plus the countdown to the next birthday.Dice RollerRoll any number of D4 to D100 dice with a modifier, using fair, cryptographically secure randomness.

Guides

All guides →

The formula is on the page

Each calculator is followed by the equation it uses, two or three worked examples with real numbers, and the mistakes people actually make.

Checked against a source

Health and money calculators cite WHO, CDC, published equations and consumer-finance guidance, and show the reference case each formula was tested on.

Runs on your device

The maths happens in your browser. Weights, salaries and loan amounts are never sent to a server, logged or stored.

Free, fast calculators that run entirely in your browser. Nothing you type is sent to a server, stored, or shared — every figure below is worked out on your own device.

Calculators

  • Percentage Calculator — Three calculators in one: find a percentage of a number, work out what percentage one number is of another, and measure percentage increase or decrease between two values.
  • Tip Calculator — Enter the bill, pick a tip percentage, and split the total across your party.
  • BMI Calculator — Calculate body mass index from height and weight in either metric or imperial units, and see which category the result falls into.
  • Loan & Mortgage Calculator — Work out the monthly payment on any amortising loan, along with the total interest you will pay over its life.
  • Salary Calculator — Convert pay between hourly, daily, weekly, monthly and annual figures, with control over hours per week and paid weeks per year.
  • TDEE Calculator — Estimate the calories you burn in a day, from your basal metabolic rate up through your activity level.
  • Grade Calculator — Add each assignment with its score and weight to see your current grade, then find out what you need on the final.
  • Age Calculator — Enter a date of birth to get an exact age broken down into years, months and days, plus the countdown to the next birthday.

How these differ from most calculator sites

Every tool here comes with the formula written out, worked examples using real numbers, and an honest account of where the method breaks down. A BMI figure without the caveats about muscle mass, or a loan payment without the note that it excludes tax and insurance, is a number that can mislead you. We would rather explain than just display.

All calculations happen in your browser using plain JavaScript. There is no account to create, no data collected about what you calculate, and nothing transmitted anywhere. Closing the tab discards everything.