Calculators & Converters
Percentage, finance, marketing, date and unit calculators with clear formulas.
What are online calculators and converters?
Online calculators and converters do everyday maths instantly: percentages, discounts, VAT, loan EMIs, compound interest, profit margins and ad campaign metrics, plus dates, ages, time zones and unit conversions for length, weight, temperature, data and more — each with the formula explained.
| I want to… | Use this tool |
|---|---|
| Work out a percentage or percentage change | Percentage Calculator |
| Calculate a monthly loan payment | Loan EMI Calculator |
| Find CPM, CPC, CTR and ROAS | CPM, CPC, CTR & ROAS Calculator |
| Count days between two dates | Date Difference Calculator |
| Convert kilograms to pounds | Weight Converter (kg, lb, oz) |
Percentage Calculator
Calculate X% of Y, what percent X is of Y, percentage change and increase or decrease by a percentage.
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Discount Calculator
Work out the sale price and savings, including stacked discounts and sales tax.
VAT / GST Calculator
Add or remove VAT, GST or sales tax at any rate and see net, tax and gross amounts.
Loan EMI Calculator
Calculate the monthly payment (EMI), total interest and yearly amortization of any loan or mortgage.
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Compound Interest Calculator
See how savings grow with compound interest and monthly contributions, year by year.
Profit Margin Calculator
Calculate gross margin, markup and profit, or the selling price needed for a target margin.
ROI Calculator
Calculate return on investment and annualised ROI (CAGR) for any investment or campaign.
CPM, CPC, CTR & ROAS Calculator
Calculate advertising metrics — CPM, CTR, CPC, conversion rate, CPA and ROAS — from your campaign numbers.
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Break-Even Calculator
Find how many units you must sell to cover fixed costs, and the revenue needed to break even.
BMI Calculator
Calculate body mass index in metric or imperial units and see the healthy weight range for your height.
Tip Calculator
Calculate the tip and split the bill between people, with optional rounding up.
Average & Statistics Calculator
Calculate the mean, median, mode, range, standard deviation, variance and quartiles of a list of numbers.
Random Number Generator
Generate secure random numbers in any range — one or thousands, unique or sorted.
Salary to Hourly Calculator
Convert pay between hourly, daily, weekly, monthly and yearly salary.
Roman Numeral Converter
Convert numbers to Roman numerals (1–3999) and Roman numerals back to numbers.
Number to Words Converter
Write numbers in words for cheques and invoices, including currency amounts and the lakh/crore system.
Age Calculator
Calculate exact age in years, months and days, total days and weeks, and days until the next birthday.
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Date Difference Calculator
Count the days, weeks, months and working days between two dates.
Add or Subtract Days from a Date
Add or subtract days, business days, weeks, months or years from any date.
Time Zone Converter
Convert a date and time between time zones worldwide, with daylight saving applied automatically.
Temperature Converter (°C, °F, K)
Convert temperatures between Celsius, Fahrenheit, Kelvin and Rankine.
Length Converter
Convert length and distance: mm, cm, m, km, inches, feet, yards, miles and nautical miles.
Weight Converter (kg, lb, oz)
Convert weight and mass: mg, g, kg, tonnes, ounces, pounds, stone and tons.
Area Converter
Convert area: square metres, square feet, acres, hectares, square miles and more.
Volume Converter
Convert volume: ml, litres, cups, fluid ounces, pints, quarts and US or UK gallons.
Speed Converter
Convert speed: km/h, mph, m/s, knots, feet per second and Mach.
Data Storage Converter (MB, GB, TB)
Convert data sizes: bits, bytes, KB, MB, GB, TB and binary KiB, MiB, GiB, TiB.
Time Unit Converter
Convert time units: milliseconds, seconds, minutes, hours, days, weeks, months and years.
Energy Converter (J, kWh, kcal, BTU)
Convert energy between joules, kilojoules, calories, kilocalories, watt-hours, kWh, BTU, electronvolts and therms.
Pressure Converter (bar, psi, Pa, atm)
Convert pressure between pascals, kPa, bar, millibar, psi, atmospheres, mmHg and inHg.
Power Converter (W, kW, hp)
Convert power between watts, kilowatts, megawatts, mechanical and metric horsepower and BTU per hour.
Frequency Converter (Hz, MHz, RPM)
Convert frequency between hertz, kHz, MHz, GHz, revolutions per minute and radians per second.
Angle Converter (Degrees, Radians)
Convert angles between degrees, radians, gradians, arcminutes, arcseconds, turns and mils.
Torque Converter (Nm, lb-ft)
Convert torque between newton-metres, pound-feet, pound-inches, kgf·m and ounce-inches.
Fuel Economy Converter (MPG, L/100km)
Convert fuel consumption between mpg (US and UK), litres per 100 km, km per litre and miles per litre.
Cooking Measurement Converter
Convert cups, tablespoons, teaspoons, millilitres, grams and ounces for flour, sugar, butter and other ingredients.
Shoe Size Converter (US, UK, EU)
Convert adult shoe sizes between US men's, US women's, UK, EU and foot length in centimetres.
Mortgage Affordability Calculator
Estimate how much house you can afford from income, debts, down payment and rate, using the 28/36 rule.
Savings Goal Calculator
Find how much to save each month to reach a savings goal by a target date, with interest.
Inflation Calculator
See how inflation affects prices and the purchasing power of money over time at any inflation rate.
Simple Interest Calculator
Calculate simple interest and the total amount for any principal, rate and time.
Credit Card Payoff Calculator
Find how long it takes to pay off a credit card and the interest you will pay — or the payment needed to clear it by a date.
SIP Calculator
Calculate the future value of a monthly SIP investment in mutual funds, with an optional yearly step-up.
Commission Calculator
Calculate sales commission and total pay from the sale amount, commission rate and base salary.
Freelance Hourly Rate Calculator
Work out the hourly and day rate to charge as a freelancer from your income goal, expenses, taxes and billable hours.
Budget Calculator (50/30/20 Rule)
Split your monthly income into needs, wants and savings with the 50/30/20 budgeting rule.
Customer Lifetime Value (LTV) Calculator
Calculate customer lifetime value and the LTV:CAC ratio from order value, purchase frequency, lifespan and margin.
Engagement Rate Calculator
Calculate social media engagement rate by followers or reach for Instagram, TikTok, LinkedIn and more.
Churn Rate Calculator
Calculate customer churn rate, retention rate and average customer lifetime for a period.
NPS Calculator (Net Promoter Score)
Calculate your Net Promoter Score from the number of promoters, passives and detractors.
A/B Test Significance Calculator
Check whether an A/B test result is statistically significant: conversion rates, lift, confidence and p-value.
Sample Size Calculator
Calculate how many survey responses you need for a confidence level and margin of error.
Calorie Calculator (TDEE & BMR)
Calculate how many calories you need a day to maintain, lose or gain weight, with BMR and macros.
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Body Fat Calculator (U.S. Navy)
Estimate body fat percentage from height, neck, waist and hip measurements with the U.S. Navy method.
Pregnancy Due Date Calculator
Find your baby’s due date from your last period, conception or IVF transfer date — with week-by-week milestones.
Ovulation Calculator (Fertile Days)
Estimate your ovulation day, fertile window and next period for the next six cycles.
GPA Calculator
Calculate your semester and cumulative GPA on the 4.0 scale from letter grades or percentages and credits.
Grade Calculator (Weighted & Final Exam)
Work out your weighted course grade and the score you need on the final exam to reach your target.
Fraction Calculator
Add, subtract, multiply and divide fractions and mixed numbers, with simplified results and steps.
Scientific Calculator
Free online scientific calculator: trigonometry, logs, powers, roots, factorials and constants, in degrees or radians.
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Quadratic Equation Solver
Solve ax² + bx + c = 0 with real or complex roots, discriminant, vertex, factored form and steps.
GCD & LCM Calculator
Find the greatest common divisor and least common multiple of two or more numbers, with Euclid’s steps.
Prime Factorization Calculator
Check if a number is prime and find its prime factors, all divisors and their sum.
Ideal Weight Calculator
Find your ideal body weight by height with the Robinson, Miller, Devine and Hamwi formulas and the healthy BMI range.
Hours Calculator (Time Card)
Add up work hours from start and end times with breaks, overnight shifts, overtime and pay.
Currency Converter (Live Exchange Rates)
Convert between 50+ currencies with daily updated exchange rates — USD, EUR, GBP, INR, LKR, AED and more.
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Week Number Calculator
Find the ISO week number of any date, the week’s start and end dates, and how many weeks the year has.
Day of the Week Calculator
Find what day of the week any date falls on — past or future — plus day of the year and leap year.
Zodiac Sign Calculator
Find your zodiac (star) sign, element and ruling planet from your birth date, plus your Chinese zodiac animal.
Retirement Calculator
Estimate your retirement savings, the income they can pay and how much you need to save each month.
Crypto Profit Calculator
Calculate crypto profit or loss, ROI and break-even price after buy and sell fees.
Stock Average Calculator
Calculate your average share price after several buys (averaging down) and your current gain or loss.
Electricity Cost Calculator
Calculate how much an appliance costs to run per day, month and year from its wattage and your electricity rate.
Trip Fuel Cost Calculator
Work out the fuel cost of a road trip from distance, fuel economy and fuel price, split between passengers.
Concrete Calculator
Calculate concrete volume for slabs, footings and columns in m³ or yd³, plus the number of premix bags.
Paint Calculator
Estimate how much paint you need for a room from the wall length, height, doors, windows and coats.
Tile Calculator (Flooring)
Calculate how many tiles or boxes you need for a floor or wall, including grout gaps and waste.
Unit Price Calculator (Best Deal)
Compare price per kg, litre or item for up to four products to find the best deal.
Running Pace Calculator
Calculate running pace per km and mile, speed, and predicted 5K, 10K, half marathon and marathon times.
Water Intake Calculator
Estimate how much water to drink per day from your weight, exercise and climate.
Sleep Calculator
Find the best time to go to bed or wake up, based on 90-minute sleep cycles.
Dog & Cat Age Calculator
Convert your dog’s or cat’s age into human years, adjusted for dog size.
Matrix Calculator
Calculate the determinant, inverse, transpose and rank of a matrix, or add, subtract and multiply two matrices.
Rounding Calculator
Round numbers to decimal places, significant figures or the nearest 10, 100 or 0.05 — with half-up, banker’s and other methods.
Permutation & Combination Calculator
Calculate nPr and nCr, with and without repetition, using exact big-number arithmetic.
Area Calculator
Calculate the area and perimeter of rectangles, squares, circles, triangles, trapezoids, ellipses and sectors.
Volume Calculator
Calculate the volume and surface area of boxes, cubes, cylinders, spheres, cones and pyramids, with litres.
Triangle Calculator
Solve triangles: angles, area and perimeter from three sides, or the missing side of a right triangle (Pythagoras).
Speed, Distance & Time Calculator
Calculate speed, distance or time — enter any two and get the third, in km/h, mph or m/s.
Ohm's Law Calculator
Calculate voltage, current, resistance and power — enter any two values (V = I × R, P = V × I).
Depreciation Calculator
Calculate asset depreciation with straight-line, declining balance, double-declining or sum-of-years methods and a full schedule.
Ratio Calculator
Solve A : B = C : D, simplify ratios, compare two ratios and list equivalent ratios.
Probability Calculator
Calculate the probability of A and B, A or B, not A, exactly one, neither, and of an event happening at least once in n tries.
One Rep Max (1RM) Calculator
Estimate your one-rep max from any set using five formulas, plus a training weight chart from 60% to 100%.
Heart Rate Zone Calculator
Find your maximum heart rate and five training zones by age, with the Karvonen method if you know your resting heart rate.
Bandwidth & Download Time Calculator
Work out how long a file takes to download at any speed, or how much monthly bandwidth a website needs.
Net Worth Calculator
Add up your assets and debts to see your net worth, debt-to-asset ratio and a breakdown of where your money is.
Debt-to-Income (DTI) Ratio Calculator
Calculate your front-end and back-end debt-to-income ratio and see how mortgage lenders will view it.
Online Stopwatch
A free online stopwatch with lap times, keyboard shortcuts and 1/100 second precision.
Countdown Timer
Set a countdown in hours, minutes and seconds or to any date — with an alarm sound and the time left in the tab title.
Pomodoro Timer
Stay focused with the Pomodoro technique: 25-minute focus sessions, short and long breaks and a sound at each change.
Dice Roller
Roll virtual dice — d4, d6, d8, d10, d12, d20 or d100 — with dice notation like 2d6+3 and fair, cryptographic randomness.