Free Online Calculators
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Popular calculators
Date Difference
Days, weeks, and years between two dates.
Age Calculator
Your exact age in years, months, and days.
Days Until Date
Countdown to any future date.
Time Zone Converter
Convert times across world time zones.
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Browse by category
Date & Time
Days between dates, age, durations.
Conversion
Length, weight, temperature, area, speed, volume.
Math
Percentages, percentage change, fractions, averages, standard deviation, ratios, GCF/LCM, exponents, square roots, quadratics, scientific notation, permutations, probability, z-scores, prime factorization, logarithms and factorials.
Finance
Loans, interest, savings, and more.
Health
BMI, calories, body metrics, ovulation and macros.
Everyday
Tips, sleep, discounts, fuel, Roman numerals, random numbers, passwords and work hours.
Geometry
Circle, rectangle, Pythagorean theorem, triangle area, cylinder, sphere, cone, trapezoid and square footage.
Education
GPA, weighted course grade, final exam score needed and a quick test grader.
Home & Garden
Paint, concrete and tile calculators for home-improvement and DIY projects.
Science
Physics essentials — density, Ohm's law and force (F = m·a).
Coming soon
Cooking
Unit swaps and recipe scaling.
All calculators
Date & Time
- Date DifferenceDays, weeks, and years between two dates.
- Age CalculatorYour exact age in years, months, and days.
- Days Until DateCountdown to any future date.
- Time Zone ConverterConvert times across world time zones.
- Add / Subtract DateAdd or subtract days, weeks, months or years from a date.
- Business DaysWorking days (Mon–Fri) between two dates.
- Time DurationHours and minutes between two times.
- Week NumberISO 8601 week number for any date.
Conversion
- Length ConverterConvert between cm, inches, feet, meters and more.
- Weight ConverterConvert between kg, lb, oz, stone and more.
- Temperature ConverterConvert Celsius, Fahrenheit and Kelvin.
- Area ConverterConvert m², ft², acres, hectares and more.
- Speed ConverterConvert km/h, mph, m/s, knots and ft/s.
- Volume ConverterConvert mL, L, US cups, pints, quarts and gallons.
- Cooking ConverterConvert cups, tablespoons, mL, oz and grams — with ingredient weights for flour, sugar, butter and more.
Math
- Percentage CalculatorPercent of, what percent, and percent change.
- Fraction CalculatorAdd, subtract, multiply or divide two fractions.
- Average CalculatorMean, median, mode, range, sum and count.
- Standard DeviationSample and population standard deviation and variance.
- Ratio CalculatorSimplify ratios and solve proportions A : B = C : D.
- GCF & LCMGreatest common factor and least common multiple of two or more numbers.
- Exponent CalculatorRaise any base to any power — positive, negative, zero or fractional exponents.
- Square Root CalculatorFind the square root of any number as a decimal and in simplified radical form, plus cube roots and other nth roots.
- Quadratic Formula CalculatorSolve ax² + bx + c = 0 with the discriminant and real or complex roots.
- Scientific Notation ConverterConvert decimals to scientific notation and back, with E-notation too.
- Permutation & CombinationCalculate nPr (order matters) and nCr (order does not) from n and r.
- Probability CalculatorSingle-event probability plus AND, OR, neither and exactly-one for two independent events.
- Z-Score CalculatorStandard score: how many standard deviations a value is from the mean, or back to a raw value.
- Percentage IncreasePercent change between two values, or increase/decrease a value by a percent.
- Prime FactorizationPrime factors of any number, written with exponents, plus a prime / composite check.
- Logarithm Calculatorlog, ln and any base — uses the change-of-base formula log_b(x) = ln(x) / ln(b).
- Factorial CalculatorExact n! for any whole number from 0 to 1000 using big-integer arithmetic.
- Number Base ConverterConvert numbers between binary, octal, decimal, hexadecimal and any base from 2 to 36.
- Slope CalculatorSlope, y-intercept, line equation, angle, distance and midpoint from two points.
- Confidence Intervalz-based confidence interval for a mean at 90%, 95% or 99% confidence.
- Significant FiguresCount significant figures in any number and round to a chosen number of sig figs.
- P-value CalculatorConvert a z-score or t-score into a p-value for one- or two-tailed tests.
- Sample Size CalculatorFind the survey sample size you need from confidence level, margin of error and population.
- Percent Error CalculatorCompare a measured value to the accepted value to see percent error and absolute error.
- Rounding CalculatorRound to decimal places or the nearest ten, hundred or thousand — half up, banker's, ceiling, floor or truncate.
- Fraction to DecimalConvert any fraction to its exact terminating or repeating decimal, with the repeating digits marked.
Finance
- Loan Payment CalculatorMonthly payment, total interest and total cost of a loan.
- Compound InterestGrow savings with daily, monthly, quarterly or yearly compounding.
- Simple InterestInterest and final balance using the simple-interest formula.
- Savings CalculatorFuture value of an initial deposit plus monthly contributions.
- Mortgage CalculatorMonthly mortgage payment with property tax and home insurance.
- Auto Loan CalculatorCar payment with sales tax, trade-in and down payment.
- Retirement CalculatorProject your retirement balance from current savings, monthly contributions and expected return.
- Debt Payoff CalculatorMonths to clear a debt at a fixed payment, or the payment needed to clear it by a target date.
- Rent vs Buy CalculatorCompare the total cost of buying a home with renting over the years you plan to stay.
- Amortization CalculatorFull loan payoff schedule with monthly payment, total interest and optional extra payments.
- Investment CalculatorProject portfolio growth from a starting amount, monthly contributions and expected return.
- Salary to HourlyConvert an annual salary to hourly, daily, weekly, biweekly or monthly pay — and back.
- Margin CalculatorProfit, gross margin and markup from cost and revenue — or the price for a target margin.
- Markup CalculatorTurn a cost and markup into a selling price, or find the markup between any cost and price.
- ROI CalculatorNet gain, total ROI and annualized ROI from any investment.
- Sales Tax CalculatorAdd sales tax to a price, or work out the pre-tax amount from a tax-included total.
Health
- BMI CalculatorBody Mass Index from weight and height (metric or imperial).
- BMR CalculatorBasal Metabolic Rate using the Mifflin-St Jeor equation.
- Calorie CalculatorDaily calories (TDEE) for maintain, lose or gain weight.
- Body Fat CalculatorBody fat percentage using the U.S. Navy circumference method.
- Ideal Weight CalculatorDevine, Robinson, Miller and Hamwi ideal-weight estimates.
- Due Date CalculatorEstimated pregnancy due date using Naegele's rule.
- Ovulation CalculatorEstimate ovulation, fertile window and next period from your last period date and cycle length.
- Macro CalculatorDaily calories and macros (40/30/30 carbs, protein, fat) from your stats, activity and goal.
- Water Intake CalculatorDaily water target in liters, ml and cups from weight and exercise.
- Protein Intake CalculatorDaily protein target (g) from your weight and activity goal.
- Calories Burned CalculatorCalories burned by activity, weight and time using MET values.
- Running Pace CalculatorPace per km and per mile, speed and even-pace splits from distance and time.
- Pregnancy CalculatorEstimated due date, current weeks and days, trimester and milestones — from LMP, due date, conception, ultrasound or IVF transfer.
- Conception CalculatorEstimated conception date, fertile window and matching due date from LMP, due date or birth date.
- Height CalculatorPredict a child's adult height from both parents' heights using the mid-parental (Tanner) method.
- Pregnancy Weight GainRecommended total and cumulative pregnancy weight gain by pre-pregnancy BMI, using the 2009 IOM guidelines.
Everyday
- Tip CalculatorWork out the tip, total bill, and split per person.
- Sleep CalculatorFind the best bedtime or wake-up time based on sleep cycles.
- Discount CalculatorSale price after a percentage off and how much you save.
- Fuel Cost CalculatorTrip fuel needed and total cost in US or metric units.
- Roman Numeral ConverterConvert numbers to Roman numerals and back (1–3999).
- Random Number GeneratorPick random numbers between any min and max, with optional unique (no repeats) mode.
- Password GeneratorStrong, random passwords generated locally with a cryptographically secure RNG.
- Hours CalculatorHours between start and end times, minus breaks — with decimal hours and optional pay.
- Aspect Ratio CalculatorFind the aspect ratio of any width and height, or resize while keeping the same ratio.
- Unit Price CalculatorPrice per unit and side-by-side compare to spot the better-value pack.
- Speed, Distance & TimeSolve for speed, distance or time — with miles, km, mph, km/h and m/s.
- Subnet CalculatorIPv4 CIDR subnet solver: network, broadcast, mask, wildcard, host range and usable hosts.
- Cost Split CalculatorSplit a bill or shared expenses fairly — equally, itemized, or by custom shares.
Geometry
- Circle CalculatorDiameter, circumference and area from the radius.
- Pythagorean TheoremFind the hypotenuse or a missing leg of a right triangle.
- Triangle Area CalculatorArea from base and height, or from three sides with Heron's formula.
- Rectangle CalculatorArea, perimeter and diagonal from length and width.
- Cylinder CalculatorVolume and total surface area from radius and height.
- Sphere CalculatorVolume and surface area from the radius.
- Cone CalculatorVolume, slant height, and lateral and total surface area from radius and height.
- Trapezoid CalculatorArea and median (midsegment) from the two parallel sides and height.
- Triangle CalculatorSolve any triangle from 3 values — SSS, SAS, ASA, AAS and the ambiguous SSA case.
- Square Footage CalculatorArea in square feet, square meters and acres from length and width in ft, in, yd or m.
- Circumference CalculatorCircumference of a circle from radius, diameter, area, or circumference itself.
Education
- GPA CalculatorCompute your grade point average on the standard 4.0 scale.
- Grade CalculatorCombine scores and weights into your overall course grade.
- Final Grade CalculatorThe score you need on the final to reach your target grade.
- Test Grade CalculatorQuick EZ grader: percentage and letter from correct / total.
Home & Garden
- Paint CalculatorGallons or liters of paint needed for a room from size, doors, windows and coats.
- Concrete CalculatorConcrete volume in cubic yards, feet and meters — plus 40, 60 and 80 lb bag counts.
- Tile CalculatorHow many floor or wall tiles you need from room size, tile size and waste %.
- Mulch CalculatorHow much mulch you need — cubic yards, cubic feet, cubic meters and 2 cu ft bags.
- Soil & Gravel CalculatorGravel, stone or soil volume and weight from area and depth (metric and imperial).
- BTU CalculatorRoom AC and heater sizing in BTU/hr by area, sun, occupants and climate.