Free Online Calculators

Nine everyday calculators that run instantly in your browser — percentages, fractions, dates, GPA, area, and more. No sign-up, no download, results the moment you stop typing.

Browse Calculators Common Questions

These are the calculators you reach for in everyday life — not the specialised financial or scientific tools, but the ones that come up while you're splitting a bill, helping a kid with homework, or figuring out how old a relative would be today. Tip percentages, discount math, days until a deadline, the duration between two clock times, semester GPA, the area of an oddly shaped room you're about to floor, the yearly cost of leaving a space heater running.

Every calculator here is built around a few principles. You don't need to memorise formulas — each tool shows the calculation it's running so you walk away knowing how the answer was reached. Outputs include the working, not just the bottom-line number, so you can double-check it or use it for homework. Inputs are forgiving: type fractions as 3/4, dates in any reasonable format, paste in a list of numbers. Everything is mobile-friendly, runs in your browser without sending your data anywhere, and gives you the answer the instant you stop typing. No accounts, no paywalls, no upsells.

All Calculators

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Nine free tools covering the math problems that come up most often in daily life, school, and around the house.

Percentage Calculator

Six modes in one tool: X% of Y, percentage change, increase, decrease, what percent is X of Y, and reverse percentage. Tip and discount math the easy way.

Fraction Calculator

Add, subtract, multiply, and divide fractions with step-by-step solutions. Auto-simplifies to lowest terms and converts between fractions, mixed numbers, and decimals.

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Age Calculator

Find your exact age in years, months, weeks, days, hours, and seconds. Includes a live countdown to your next birthday and works for any date.

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Date Calculator

Days, weeks, months, and years between two dates — or add and subtract days from any date to find a deadline, anniversary, or milestone.

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Time Duration Calculator

Hours, minutes, and seconds between two times. Add or subtract spans and total multiple time blocks — useful for timesheets, study sessions, and travel.

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GPA Calculator

Compute semester and cumulative grade point average with letter grades, percentages, or the 4.0 scale. Add credit hours per course for weighted GPAs.

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Area Calculator

Area for rectangles, circles, triangles, trapezoids, and combined shapes. Outputs in square feet, square metres, or square yards — sized for flooring and landscaping.

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Electricity Cost Calculator

Estimate the running cost of any appliance. Enter wattage, hours used per day, and your kWh rate to see daily, monthly, and yearly costs.

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Randomizer

Random number generator with custom ranges, dice roller, coin flipper, and list picker. Truly random results for games, raffles, and decisions.

FAQ

Common calculator questions

Quick answers to the questions people search for most when they reach a calculator page.

To find X% of a number, multiply the number by X and divide by 100. So 15% of 80 is (80 × 15) ÷ 100 = 12. For tips and discounts most people work in their head: 10% is the number with the decimal moved one place left (10% of 80 = 8), and you double or halve that for 20% or 5%. The percentage calculator handles all six common variations including percentage change and "what percent is X of Y", and shows the formula it's using so you can learn it as you go.

You can't add fractions with different denominators directly — first you have to give them a common denominator. The shortcut is to multiply each fraction's top and bottom by the other fraction's denominator. For example, 1/2 + 1/3 becomes 3/6 + 2/6 = 5/6. Then simplify if possible. The fraction calculator does this automatically for addition, subtraction, multiplication, and division, and shows every step so it's useful for homework as well as quick answers.

Subtract the birth year from the current year for years, then check the months and days: if today's month and day haven't reached the birth month and day yet, subtract one year. The leftover months and days give you the precise breakdown. This sounds simple but gets fiddly across leap years and month-length differences, which is why the age calculator handles it for you and also gives age in weeks, days, hours, and seconds — plus a countdown to the next birthday.

Compound interest is calculated as A = P(1 + r/n)^(nt), where P is the principal, r is the annual interest rate as a decimal, n is the number of times interest compounds per year, and t is the number of years. The result A is the final balance including interest. For everyday savings comparisons, the difference between compounding monthly versus annually is small but real over long periods. For loan and savings math you'll want our finance hub at free finance calculators — the percentage calculator on this page covers simple percentage growth but not compounding.

Break the shape into rectangles, triangles, and circles, calculate the area of each piece separately, then add them together. For an L-shaped room, slice it into two rectangles. For a curved corner, treat it as a quarter-circle and add or subtract its area. The area calculator covers each individual shape — run it once per piece and total the results. For flooring and landscaping, add 5–10% extra to your final number to cover waste and offcuts.

Convert both times to minutes since midnight, subtract, then convert back to hours and minutes. So 2:45 PM (885 min) minus 9:30 AM (570 min) is 315 min, or 5 hours 15 minutes. If the end time is the next day (a midnight-spanning shift, for example), add 24 hours to it before subtracting. The time duration calculator handles overnight spans automatically and lets you total multiple blocks for timesheets and study tracking.

Each letter grade maps to a number on the 4.0 scale: A = 4.0, B = 3.0, C = 2.0, D = 1.0, F = 0. Each course's grade is multiplied by its credit hours to give "grade points", you sum the grade points across all courses, and then divide by total credit hours. So three courses earning A (3 cr), B (4 cr), and A (3 cr) give (12 + 12 + 12) / 10 = 3.6 GPA. The GPA calculator handles plus/minus grades, percentage inputs, and cumulative GPA across multiple semesters.

Multiply the appliance's wattage by the hours it runs to get watt-hours, divide by 1000 to get kilowatt-hours (kWh), then multiply by your electricity rate per kWh. A 1500 W space heater running 8 hours uses 12 kWh, which at $0.15/kWh costs $1.80 per day — about $54 a month. Find your rate on a recent power bill (the per-kWh number, not the total). The electricity cost calculator projects daily, monthly, and yearly totals so you can spot the appliances quietly running up your bill.

Free Online Calculators

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Common calculator questions

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