All Online Calculators
59 useful tools. Eight ways to explore. All free.
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Math & Numbers
10 toolsFrom everyday percentages to scientific expressions. Make numbers make sense.
Percentage Calculator
Find a percentage of a number, a percentage share, or the whole from a known part.
Math & NumbersPercentage Change Calculator
Measure the relative increase or decrease between an original and a new value.
Math & NumbersFraction Calculator
Work with fractions and mixed numbers, simplify a fraction, or convert a decimal exactly.
Math & NumbersAverage Calculator
Calculate the arithmetic mean, median, sum, and range of a list.
Math & NumbersRatio Calculator
Simplify ratios, scale two quantities, or solve the missing quantity in a proportion.
Math & NumbersScientific Calculator
Evaluate arithmetic, powers, roots, logarithms, and trigonometric expressions.
Math & NumbersStandard Deviation Calculator
Measure the spread of a population or sample with variance and mean.
Math & NumbersExponent Calculator
Raise a base to a power and inspect the resulting real number.
Math & NumbersGCF & LCM Calculator
Find the greatest common factor and least common multiple of integers.
Math & NumbersRandom Number Generator
Generate one or many random integers, with optional unique sampling.
Math & NumbersDate & Time
7 toolsCount calendar days, plan working time, and compare clocks around the world.
Age Calculator
Find calendar age in years, months, days, and total days.
Date & TimeDate Difference Calculator
Count days and weeks between two calendar dates.
Date & TimeTime Duration Calculator
Calculate elapsed hours and minutes, including overnight periods.
Date & TimeBusiness Days Calculator
Count Monday–Friday working days with optional holiday exclusions.
Date & TimeTime Zone Difference Calculator
Compare two IANA time zones at a specific UTC instant, including daylight saving.
Date & TimeWork Hours Calculator
Calculate paid time and gross pay after unpaid breaks.
Date & TimeBirth Year Calculator
Find your possible birth years from a completed age and reference date, or use birthday information to narrow the answer.
Date & TimeUnit Conversion
6 toolsMove between metric and imperial measurements with clear, reversible conversions.
Length Converter
Convert length measurements between common units with a reversible conversion.
Unit ConversionWeight Converter
Convert weight measurements between common units with a reversible conversion.
Unit ConversionTemperature Converter
Convert temperature measurements between common units with a reversible conversion.
Unit ConversionArea Converter
Convert area measurements between common units with a reversible conversion.
Unit ConversionVolume Converter
Convert volume measurements between common units with a reversible conversion.
Unit ConversionSpeed Converter
Convert speed measurements between common units with a reversible conversion.
Unit ConversionFinance
11 toolsExplore borrowing, saving, and investing with transparent assumptions.
Loan Payment Calculator
Estimate fixed monthly loan payments, total interest, and total repayment.
FinanceMortgage Calculator
Estimate a mortgage’s monthly payment with property tax, insurance, and HOA costs.
FinanceCompound Interest Calculator
Project growth with periodic compounding and end-of-period contributions.
FinanceSavings Goal Calculator
Find the monthly deposit needed to reach a future savings target.
FinanceAPR to APY Calculator
Convert a nominal annual interest rate into an effective annual yield.
FinanceAmortization Schedule Calculator
Explore every monthly payment and the effect of extra principal payments.
FinanceRetirement Savings Calculator
Project your savings balance at retirement with monthly contributions.
FinanceInvestment Return Calculator
Calculate net investment gain, total return, and annualized growth.
FinanceSimple Interest Calculator
Calculate interest charged only on the original principal.
FinanceRent Affordability Calculator
Estimate how much monthly rent fits your income, essential expenses, debt and savings, with configurable budget scenarios.
FinanceHouse Affordability Calculator
Estimate an affordable home price from household income or a monthly budget, including loan payments and recurring ownership costs.
FinanceHealth & Fitness
12 toolsUnderstand common adult health estimates and plan your next run.
BMI Calculator
Calculate adult body mass index with metric or imperial measurements.
Health & FitnessCalorie Needs Calculator
Estimate adult maintenance energy needs from resting metabolism and activity.
Health & FitnessBMR Calculator
Compare adult resting-energy estimates from Mifflin–St Jeor and revised Harris–Benedict.
Health & FitnessBody Fat Estimate Calculator
Compare circumference and adult BMI-based body-fat estimates, including estimated fat and lean mass.
Health & FitnessRunning Pace Calculator
Calculate running pace, speed, or finish time from distance and duration.
Health & FitnessHeart Rate Zones Calculator
Estimate five exercise intensity zones using maximum heart rate or heart-rate reserve.
Health & FitnessWater Intake Calculator
Estimate daily total water from food and beverages using adult reference intakes, with activity context and optional fluid tracking.
Health & FitnessProtein Calculator
Estimate daily protein in grams from body weight, distinguishing the general adult reference from regular exercise and training ranges.
Health & FitnessPregnancy Calculator
Explore estimated conception timing and gestational age from your period, due date, conception date, ultrasound or IVF transfer.
Health & FitnessDue Date Calculator
Estimate when your baby is due using period dates, a supplied conception date, ultrasound gestational age or IVF transfer details.
Health & FitnessOvulation Calculator
Estimate ovulation, fertile-window dates and the next period from your cycle length, with optional cycle variation and a calendar.
Health & FitnessBlood Alcohol Content Calculator
Explore a rough educational BAC model using body weight, drink volumes, alcohol strengths and elapsed time, with explicit uncertainty.
Health & FitnessEducation
4 toolsCheck grades, compare credit-weighted averages, and plan your study goals.
GPA Calculator
Calculate course, semester and cumulative GPA using numeric, letter or percentage grades, or plan a target GPA.
EducationFinal Grade Calculator
Find the exam score needed to achieve a target overall course grade.
EducationWeighted GPA Calculator
Calculate course-bonus weighted GPA, semester totals and cumulative GPA using an explicit grading scale.
EducationTest Score Percentage Calculator
Turn earned points into a percentage and find missed points.
EducationConstruction & Home
4 toolsEstimate materials for your next project, with room for waste and real-world variation.
Concrete Calculator
Estimate concrete volume, weight, bags and cost for slabs, columns, tubes, curbs and stairs.
Construction & HomePaint Calculator
Estimate paint quantity from wall area, openings, coats, and coverage.
Construction & HomeFlooring Calculator
Estimate flooring area, packs to buy, and total material cost.
Construction & HomeTile Calculator
Estimate tiles, boxes and cost from dimensions or area, including a gap or overlap and waste allowance.
Construction & HomeBusiness & Everyday
5 toolsUnderstand costs, prices, tax, and the numbers behind everyday decisions.
Profit Margin Calculator
Find gross profit, margin, and markup from cost and selling price.
Business & EverydaySales Tax Calculator
Add tax to a net price or extract included tax from a gross price.
Business & EverydayMarkup Calculator
Calculate a selling price by applying a markup to cost.
Business & EverydayBreak-Even Calculator
Estimate the whole-unit sales needed to cover fixed and variable costs.
Business & EverydayROI Calculator
Calculate net return and return on investment from total cost and proceeds.
Business & EverydayHow do I find the right calculator?
Browse a category above or filter by the question you need to answer. Choose a calculator card to open its inputs, formula, worked example, and limitations. Calorie Calculator opens the existing Calorie Needs tool, while Unit Converter opens the conversion category with six focused converters.
Every published tool is linked in this directory even without search. Financial projections, health measures, and material quantities should be interpreted with the assumptions on their individual pages.