Calculators
Fast, free calculators for everyday math, dates, percentages, and more.
Aspect Ratio Calculator
Work out aspect ratios and resize dimensions — one click for 16:9, 4:3, 1:1, 9:16, 3:2, 21:9 or A4, or find the missing width or height, with the shape drawn.
CalculatorsPercentage Calculator
Six percentage calculations on one page — X% of a value, what percent of what, change, difference, add or take off a percent, work back to the original.
CalculatorsAge Calculator
Exact age in years, months, weeks and days from a date of birth — plus the total in months, weeks, days, hours, minutes and seconds, and your next birthday.
CalculatorsDate Difference Calculator
Find the time between two dates in days, working days, weeks, months, years and hours — with your own weekend and your own days off. Free, in your browser.
CalculatorsDiscount Calculator
Work out the sale price after one discount or several stacked, the percent off between two prices, or the original price. Free, no sign-up, in your browser.
CalculatorsGCD & LCM Calculator
Find the GCD and LCM of any list of integers and see the working — the prime factor table, the Euclidean algorithm step by step, and every shared divisor.
CalculatorsPrime Checker & Factorization
Check whether a number is prime, see its prime factorisation and every divisor, find the nearest primes either side, and list the primes between two numbers.
CalculatorsVAT Calculator
Add or remove VAT, GST or sales tax to get the gross, net and tax amounts instantly, with one-click rates for the UK, Germany, Japan and more. Free, no signup.
CalculatorsCompound Interest Calculator
Ten compounding frequencies, a deposit schedule of its own, tax and inflation — or solve for the principal, rate or time needed. All in your browser.
CalculatorsFraction Simplifier
Reduce a fraction to lowest terms, add, subtract, multiply and divide fractions, and convert between fractions and decimals. Free, no sign-up, in your browser.
CalculatorsMargin & Markup Calculator
Turn cost and revenue into profit, profit margin % and markup %, or work out the revenue needed to hit a target margin — 100% in your browser, no upload.
CalculatorsStatistics Calculator
Paste numbers for the count, sum, mean, median, mode, range, quartiles, IQR, variance and standard deviation — with a histogram, a box plot and the outliers.
CalculatorsFactorial, Permutations & Combinations Calculator
Compute n!, nPr and nCr exactly with big-integer arithmetic, plus the digit count and scientific notation for numbers far too long to print. Free, no signup.
CalculatorsQuadratic Equation Solver
Solve any quadratic ax² + bx + c = 0 for its roots, discriminant and vertex, see the parabola drawn, and follow the formula step by step. Free, no upload.
CalculatorsISO Week Number Calculator
Find the week number of any date, or the dates in any week, under ISO 8601, the US convention or a Saturday start — with the month drawn as a calendar to check.
CalculatorsCircle Calculator
Enter a radius, diameter, circumference or area and get the other three — with the circle drawn, the unit label you pick, and arc, chord and sector areas.
CalculatorsPythagorean Theorem Calculator
Solve a right triangle from any two of its sides, angles, area or perimeter — drawn to scale, with the working shown, the altitude and the circle radii.
CalculatorsTime Ago Calculator
Turn a date into a phrase like 3 hours ago, or a phrase or raw timestamp back into a date — with local time, UTC and Unix seconds. Free, in your browser.
CalculatorsAdd or Subtract Days Calculator
Add or subtract years, months, weeks and days from a date — or count forward in business days with your own weekend and days off. Free, in your browser.
CalculatorsLeap Year Checker
Instantly check whether any year is a leap year, see why, how many days it has, and the next leap years — runs 100% in your browser with no upload.
CalculatorsSlope Calculator (Two Points)
Find the slope, y-intercept, equation and angle of the line through two points — with the line drawn, plus the distance, midpoint and perpendicular slope.
CalculatorsBusiness Days Calculator
Count the working days between two dates with your own weekend and your own days off, or find the date N business days away. Free, in your browser, no upload.
CalculatorsDay of the Week Finder
Find out what day of the week any date falls on, plus its day-of-year and whether it is a weekend — runs 100% in your browser with no upload.
CalculatorsDistance & Midpoint Calculator
Calculate the straight-line distance and midpoint between two 2D points from their x and y coordinates — runs 100% in your browser with no upload.
CalculatorsFibonacci Sequence Generator & Nth Term Calculator
Generate the first N Fibonacci numbers or find the exact Nth term with BigInt precision — runs 100% in your browser with no upload.
CalculatorsProportion Calculator (a/b = c/d)
Solve a proportion a/b = c/d by entering any three values and leaving one blank — runs 100% in your browser with no upload.
CalculatorsDays in Month Calculator
Instantly find how many days are in any month of any year, with leap years handled automatically — runs 100% in your browser with no upload.
CalculatorsOhm's Law Calculator
Enter any two of voltage, current, resistance, or power and this Ohm's law calculator instantly finds the other two — runs 100% in your browser with no upload.
CalculatorsScientific Notation Converter
Convert any number to and from scientific and engineering notation instantly — runs 100% in your browser with no upload.
CalculatorsZodiac Sign Finder
Find your Western star sign and Chinese zodiac animal from any birth date — runs 100% in your browser with no upload.
CalculatorsGolden Ratio Calculator (Phi 1.618)
Enter the longer, shorter, or whole segment and instantly get all golden-ratio (phi = 1.618) values — runs 100% in your browser with no upload.
CalculatorsMoon Phase Calculator
Find the moon phase and approximate illumination percentage for any date — runs 100% in your browser with no upload.
CalculatorsWeighted Average Calculator
Enter value and weight pairs to instantly compute a weighted average and total weight — runs 100% in your browser with nothing uploaded.
CalculatorsLogarithm Calculator (log any base, ln, log10)
Calculate the logarithm of any number in any base, plus natural log (ln) and log base 10 — runs 100% in your browser with no upload.
CalculatorsNth Root Calculator
Calculate the square root, cube root, or any nth root of a number instantly — runs 100% in your browser with no upload.
CalculatorsArithmetic Sequence Calculator
List every term, find the Nth term and add up an arithmetic sequence from its first term and common difference. Free, in your browser, nothing uploaded.
CalculatorsTime Duration Calculator (Add & Subtract HH:MM:SS)
Add and subtract time durations in HH:MM:SS or MM:SS, one per line with an optional + or −, and get the running total live. Free, in your browser.
CalculatorsEaster Date Calculator
Find the exact date of Western (Gregorian) Easter Sunday for any year using the Meeus/Jones/Butcher algorithm — runs 100% in your browser with no upload.
CalculatorsGeometric Sequence Calculator
List every term, find the Nth term, and compute the sum of a geometric sequence from its first term and common ratio — runs 100% in your browser with no upload.
CalculatorsSimple Interest Calculator
Work out the interest and the total amount on a principal from an annual rate and a term in years, months or days. Free, no sign-up, in your browser.
CalculatorsTime Card Calculator
Enter clock-in and clock-out times with optional break minutes to get decimal hours worked per day and a weekly total — 100% in your browser, no upload.
CalculatorsJulian Day Number Converter
Convert any Gregorian calendar date to its astronomical Julian Day Number and back, instantly — runs 100% in your browser with no upload.
CalculatorsSignificant Figures Rounder
Round any number to a chosen number of significant figures instantly — runs 100% in your browser with no upload.
CalculatorsBMI Calculator
BMI from height and weight, metric or imperial — the WHO class, BMI Prime, ponderal index, healthy weight range, and how much to gain or lose. No upload.
CalculatorsLoan & Mortgage Calculator
Monthly payment, total interest and a dated amortization schedule for any loan or mortgage — biweekly and weekly options, PMI, taxes, APR and CSV. No upload.
CalculatorsTip Calculator
Work out the tip, total and per-person amount for any bill, with quick 10–25% presets and bill splitting — 100% in your browser, no upload.
CalculatorsCalorie Calculator (TDEE & BMR)
Estimate your daily calorie needs — BMR, maintenance (TDEE) and weight-loss or gain targets — using the Mifflin–St Jeor equation, 100% in your browser.
CalculatorsGPA Calculator
Calculate your weighted grade point average on the 4.0 scale from each course's letter grade and credit hours — 100% in your browser, no upload.
CalculatorsSalary Calculator — Hourly ↔ Annual Pay Converter
Convert pay between hourly, daily, weekly, monthly and annual — set your own hours per week and weeks per year. Free, instant and 100% in your browser.
CalculatorsRunning Pace Calculator — min/km, min/mile & Finish Times
Enter a distance and time to get your pace per km and per mile, speed, and predicted 5K, 10K, half and full marathon finish times. Free, in your browser.
CalculatorsGrade Calculator — Test Score % and Final Grade Needed
Turn correct answers into a percentage and letter grade, or work out the score you need on the final to hit your target. Free, instant, in your browser.
CalculatorsFuel Cost Calculator — Trip Gas & Petrol Cost
Estimate what a trip costs in fuel from distance, fuel economy and price — miles or km, mpg, L/100km or km/L — split per passenger. Free, in your browser.
CalculatorsBody Fat Calculator — U.S. Navy Method
Estimate your body fat percentage from tape measurements using the U.S. Navy circumference method — metric or imperial. Free, private, 100% in your browser.
CalculatorsSleep Calculator — Bedtime & Wake-Up Time
Find the best time to sleep or wake based on 90-minute sleep cycles. Enter a time and get bedtime or wake-up suggestions. Free, in your browser.
CalculatorsElectricity Cost Calculator — Appliance Running Cost
Work out what an appliance costs to run per day, month and year from its wattage, hours of use and your electricity rate. Free, 100% in your browser.
CalculatorsPaint Calculator — How Much Paint You Need
Estimate how many gallons or litres of paint a room needs from wall size, doors, windows and coats. Metric or imperial, free, in your browser.
CalculatorsConcrete Calculator — Cubic Yards & Bags
Calculate concrete volume for a slab or footing in cubic yards, metres and feet, plus how many 40/60/80 lb bags you need. Free, in your browser.
CalculatorsPregnancy Due Date Calculator (Naegele’s Rule)
Estimate your pregnancy due date from your last menstrual period, and see how many weeks along you are. An estimate, not medical advice. In your browser.
CalculatorsSquare Footage Calculator — Area of a Room
Add up the square footage (and square metres) of one or more rooms, with an optional total cost per square foot. Free, in your browser.
CalculatorsTile Calculator — Tiles & Boxes Needed
Work out how many tiles and boxes you need for a floor or wall from the area, tile size and a waste allowance. Metric or imperial, in your browser.
CalculatorsIdeal Weight Calculator (Devine, Robinson, Miller, Hamwi)
Estimate ideal body weight from height and sex using four classic clinical formulas, plus the healthy BMI weight range. Free, in your browser.
CalculatorsUnit Price Calculator — Cost Per Unit & Best Value
Compare products by price per unit to find the best value. Enter each option’s price and amount; the cheapest per unit is highlighted. In your browser.
CalculatorsWater Intake Calculator — Daily Water Needs
Estimate how much water to drink a day from your weight, exercise and climate — in litres, ounces and cups. A general guide, in your browser.
CalculatorsOne-Rep Max (1RM) Calculator + Training Loads
Estimate your one-rep max from a weight and reps using the Epley and Brzycki formulas, with a percentage table of training loads. In your browser.
CalculatorsDog Age Calculator — Dog Years to Human Years
Convert your dog’s age to human years using a size-adjusted model and the 2019 epigenetic-clock formula. Free, in your browser.
CalculatorsTimer, Stopwatch & Pomodoro
A countdown timer, a stopwatch with laps, and a Pomodoro focus cycle with a beep and optional desktop alert — 100% in your browser, no upload.
CalculatorsMath Expression Evaluator
Evaluate free-form math expressions with functions, constants and degree-based trig — one per line, with variables. 100% in your browser, no upload
CalculatorsGreat-Circle Distance & Bearing Calculator
Find the great-circle distance and initial compass bearing between two latitude and longitude points, in kilometers, miles and meters. Free, no upload.
CalculatorsTime to Decimal Converter (HH:MM ⇄ Hours)
Convert clock time like 2:30 to decimal hours (2.5) and back for timesheets and payroll — 100% in your browser, no upload.
CalculatorsETA Calculator
Estimate when a task will finish from how much is done, the total, and the time elapsed — 100% in your browser, no upload
Everyday arithmetic that is annoying to get right by hand. The dates group answers how long between two dates, how old something is, when a due date lands, and what a duration is in decimal hours for a timesheet. The money group covers salary, unit price comparisons, fuel, electricity and paint or tiles for a room.
The health and fitness group — body fat, ideal weight, water intake, one-rep max, sleep, pace — are the standard published formulas, and they are estimates by nature. They are useful for tracking a change over time and not a substitute for anyone qualified.
The rest are the ones you reach for mid-task: percentage in all four directions (of, increase, decrease, what percent), aspect ratio for resizing without distortion, square footage and concrete for a job, geo distance between two coordinates, and a plain expression evaluator for when you just want to type the sum.