Free Online Calculators for Everyday Needs
Free online calculators for math, finance, health, everyday life, and more.
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Quick calculator
Scientific ↗Ready when you are.
% divides a value by 100. Try 200 × 10%.
Popular calculators
21 essentialsA curated collection for everyday calculations.
Percentage Calculator
Percentages, parts, and whole amounts.
Math & NumbersAge Calculator
Your age in years, months, and days.
Date & TimeBMI Calculator
Understand your adult body mass index.
Health & FitnessCalorie Calculator
Estimate your daily maintenance energy.
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 & FitnessPregnancy Calculator
Explore estimated conception timing and gestational age from your period, due date, conception date, ultrasound or IVF transfer.
Health & FitnessOvulation Calculator
Estimate ovulation, fertile-window dates and the next period from your cycle length, with optional cycle variation and a calendar.
Health & FitnessProtein Calculator
Estimate daily protein in grams from body weight, distinguishing the general adult reference from regular exercise and training ranges.
Health & FitnessMortgage Calculator
A clearer view of monthly home costs.
FinanceLoan Calculator
Monthly payments and total interest.
FinanceHouse Affordability Calculator
Estimate an affordable home price from household income or a monthly budget, including loan payments and recurring ownership costs.
FinanceRent Affordability Calculator
Estimate how much monthly rent fits your income, essential expenses, debt and savings, with configurable budget scenarios.
FinanceWater Intake Calculator
Estimate daily total water from food and beverages using adult reference intakes, with activity context and optional fluid tracking.
Health & FitnessCompound Interest Calculator
See what regular saving could become.
FinanceFraction Calculator
Add, subtract, multiply, and simplify.
Math & NumbersScientific Calculator
Powers, roots, logs, and trigonometry.
Math & NumbersDate Difference Calculator
Count the days between two dates.
Date & TimeUnit Converter
Convert length, weight, temperature, and more.
Unit ConversionGPA Calculator
Find your credit-weighted grade average.
EducationBirth Year Calculator
Find your possible birth years from a completed age and reference date, or use birthday information to narrow the answer.
Date & TimeBlood Alcohol Content Calculator
Explore a rough educational BAC model using body weight, drink volumes, alcohol strengths and elapsed time, with explicit uncertainty.
Health & FitnessPick your category.
Everything, in its right place.
Math & Numbers
10 toolsFrom everyday percentages to scientific expressions. Make numbers make sense.
- Percentage
- Percentage Change
- Fraction
- Average
- Ratio
- Scientific
- Standard Deviation
- Exponent
- GCF & LCM
- Random Number Generator
Date & Time
7 toolsCount calendar days, plan working time, and compare clocks around the world.
View all date & timeUnit Conversion
6 toolsMove between metric and imperial measurements with clear, reversible conversions.
View all unit conversionFinance
11 toolsExplore borrowing, saving, and investing with transparent assumptions.
- Loan Payment
- Mortgage
- Compound Interest
- Savings Goal
- APR to APY
- Amortization Schedule
- Retirement Savings
- Investment Return
- Simple Interest
- Rent Affordability
- House Affordability
Health & Fitness
12 toolsUnderstand common adult health estimates and plan your next run.
- BMI
- Calorie Needs
- BMR
- Body Fat Estimate
- Running Pace
- Heart Rate Zones
- Water Intake
- Protein
- Pregnancy
- Due Date
- Ovulation
- Blood Alcohol Content
Education
4 toolsCheck grades, compare credit-weighted averages, and plan your study goals.
View all educationConstruction & Home
4 toolsEstimate materials for your next project, with room for waste and real-world variation.
View all construction & homeBusiness & Everyday
5 toolsUnderstand costs, prices, tax, and the numbers behind everyday decisions.
View all business & everydayYour workspace
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Search by name, browse every category, or return to a saved tool.
Your numbers stay yours
Calculations happen in your browser. No account, no submitted inputs.
More than just an answer
See the formula, follow a worked example, and understand the assumptions.
Built for everyday decisions
Clear units, helpful validation, and answers you can copy and use.
About this website
Using online calculators
Which type of calculator is best for my task?
Choose a tool that matches the question: a basic calculator for everyday arithmetic, a scientific calculator for powers and trigonometry, or a dedicated tool for dates, loans, or unit conversions. Check the units and assumptions before using the answer.
How do I use an online calculator?
Enter your values, check units and settings, and select Calculate. On the homepage keypad, type or tap an expression and press equals. Read the result label and use the worked example to check that you chose the right operation.
What is the difference between a basic and a scientific calculator?
A basic calculator handles arithmetic such as addition, subtraction, multiplication, and division. A scientific calculator adds functions such as powers, roots, logarithms, and trigonometry. Check degrees versus radians for angle calculations.
How do I calculate percentages on a calculator?
Use percentage ÷ 100 × number: 15 ÷ 100 × 200 = 30. To find a part’s percentage of a whole, use part ÷ whole × 100. The homepage percent key divides the preceding value by 100, so 200 × 10% gives 20.