Free Online Calculators

Fast, accurate calculators for finance, health, math and everyday life. No sign-up, no downloads — every tool runs instantly in your browser, with formulas explained and sources cited.

Browse calculators How we verify our math →

Finance Calculators

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FINANCE
Paycheck Calculator
See exactly what lands in your bank account each payday — after federal tax, FICA, and state tax.
FINANCE
Refinance Break-Even Calculator
See how many months of lower payments it takes to recover your closing costs — and whether refinancing is actually worth it.
FINANCE
Pay Raise Calculator
See exactly what that raise means — your new salary, the extra per paycheck, and the hourly equivalent.
FINANCE
Salary to Hourly Calculator
Convert salary to hourly (or hourly to salary) in seconds — adjusted for your actual hours, not just the standard 40.
FINANCE
HYSA Calculator
See how fast your savings grow in a high-yield account — or find out exactly how much you're missing out by staying in a regular one.
FINANCE
Compound Interest Calculator
Watch your money grow — project compound growth with deposits, any rate, any timeframe, and see what starting 10 years earlier would do.
FINANCE
Daily Compound Interest Calculator
See what daily compounding does for your savings — with monthly deposits and a side-by-side monthly comparison.
FINANCE
Tip Calculator
Tip on the pre-tax amount, split to the cent, and see what each person owes — in seconds.
FINANCE
Discount Calculator
Find the real sale price in seconds — including stacked discounts, coupons, multi-buy deals, and the reverse math stores hope you won't do.
FINANCE
Sales Tax Calculator
Add sales tax to any price — or work backwards from the total — with state and local tax shown as two separate lines.
FINANCE
Currency Converter
Convert between world currencies with live mid-market rates — plus the honest truth about fees.
FINANCE
Loan Calculator
Figure out your monthly loan payment, total interest, and payoff date — with a year-by-year breakdown of where every dollar goes.

Health Calculators

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HEALTH
TDEE Calculator
Discover how many calories you burn per day — and what to eat to lose, maintain, or gain weight.
HEALTH
Body Fat Calculator
Find your estimated body fat percentage with just a tape measure — plus your fat mass, lean mass, and fitness category.
HEALTH
Protein Intake Calculator
How much protein do you really need? Get a research-backed daily target for your weight and goal — plus a simple per-meal breakdown.
HEALTH
BMR Calculator
Your body burns calories even doing nothing. Find your Basal Metabolic Rate — the foundation of every calorie plan.
HEALTH
Macro Calculator
Turn your calorie target into daily protein, carbs, and fat grams — pick a proven split or dial in your own.
HEALTH
Water Intake Calculator
Forget the "8 glasses" myth — get a hydration target matched to your weight, your activity, and your climate.
HEALTH
Ideal Weight Calculator
See the classic clinical weight formulas side by side — Devine, Robinson, Miller — plus your healthy BMI range.
HEALTH
Due Date Calculator
When will your baby arrive? Get an estimated due date from your last period or conception date — plus how far along you are today.
HEALTH
Heart Rate Zones Calculator
Stop guessing your effort — get your 5 heart rate training zones from your age, personalized with your resting heart rate.
HEALTH
Pace Calculator
Pace, time, distance — know any two, get the third instantly. Works in kilometers and miles.
HEALTH
BMI Calculator
Check your Body Mass Index in seconds — metric or imperial — and see what your number means for your health.

Math Calculators

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MATH
Casio Scientific Calculators
Six Casio models in your browser — fx-991EX, fx-580VN X, fx-991ES Plus, fx-991CW and more, with textbook display.
MATH
Percentage Calculator
Find any percentage in seconds — what X% of a number is, percent change between two values, and more.
MATH
Average Calculator
Mean, median and mode side by side — plus weighted averages, sorted data, and a quick visual chart.
MATH
Fraction Calculator
Add, subtract, multiply, divide and simplify fractions — with every step shown, plus mixed numbers and decimals.
MATH
Ratio Calculator
Simplify ratios, solve proportions, and scale recipes or plans to any size — ratio, decimal and percent together.
MATH
Scientific Calculator
A realistic Casio-style scientific calculator in your browser — pick from 17 models (fx-991EX, fx-991ES Plus, fx-991CW, fx-580VN X and more), tap the keys like the real thing, and read fractions stacked exactly like your textbook. SHIFT/ALPHA keys, trig, logs, exponents, equation systems, matrices and statistics, with keyboard-first input.
MATH
Standard Deviation Calculator
Find standard deviation and variance for any dataset — population or sample — with every step shown.
MATH
Graphing Calculator
Plot any function of x on an interactive graph - drag to pan, scroll to zoom, add up to 5 functions in different colors, and read values straight off the curve.
MATH
Equation Solver
Solve linear equations, quadratics, two-equation systems and inequalities - with every step written out the way your teacher expects.
MATH
Matrix Calculator
Add, subtract, multiply, and invert 2x2 and 3x3 matrices - with every step shown, from the determinant to the final inverse.
MATH
Statistics Calculator
Full descriptive statistics for any dataset - mean, median, mode, standard deviation, quartiles - plus a histogram and box plot drawn instantly.

Everyday Calculators

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EVERYDAY
Cooking Converter
Convert cups to grams, ounces to milliliters, and scale any recipe up or down — with per-ingredient weights.
EVERYDAY
Fuel Cost Calculator
Estimate any trip's fuel cost from distance, fuel efficiency and gas price — plus cost per mile and per person.

Time Calculators

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TIME
Age Calculator
Your exact age in years, months and days — plus total days lived, your birth weekday, zodiac signs, and next-birthday countdown.
TIME
Date Duration Calculator
Count days, weeks and months between any two dates — or count down to an event, with an optional business-days mode.
TIME
Hours Calculator
Add up work hours, build a weekly timesheet, or find the time between two clock readings — in HH:MM and decimal hours.
TIME
Time Calculator
Add and subtract time, measure durations between two times, and convert between seconds, minutes, hours, days and weeks.
TIME
Time Zone Converter
Convert time across world zones instantly — with daylight saving handled and a meeting planner for US, EU and Asia.

Education Calculators

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EDUCATION
GPA Calculator
Find your semester and cumulative GPA in seconds — unweighted or weighted, high school or college.
EDUCATION
Grade Calculator
Find out exactly what you need on the final — or compute your weighted grade across categories.

Unit Converters

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CONVERTERS
Celsius to Fahrenheit Converter
Convert °C to °F (and back) instantly — with the formula, everyday reference points, and a quick chart.
CONVERTERS
Cm to Inches Converter
Convert centimeters to inches (and back) instantly — with the formula, a quick chart, and feet+inches breakdown.
CONVERTERS
Kg to Lbs Converter
Convert kilograms to pounds (and back) instantly — with the formula, a quick chart, and stone breakdown for UK readers.
CONVERTERS
Unit Converter
Convert length, weight, temperature, volume and speed instantly — metric to imperial made easy.

What is SlickCalcs?

SlickCalcs is a free library of online calculators for everyday decisions: figuring out your paycheck, planning a loan, tracking calories, or solving a math problem. Every calculator is built for regular people — no finance degree or math background needed. Type in your numbers, get a clear answer in plain English, and see exactly how the math works.

Who is it for? Anyone in the US (and beyond) who wants a quick, trustworthy number: employees checking their take-home pay, families budgeting a mortgage, students doing homework, or anyone comparing prices, tips, and savings. If you've ever Googled "how much will I..." — this site is for you.

Why trust the answers? Each tool shows its formula, a worked example with real numbers, and the authoritative source it comes from (the IRS, peer-reviewed research, standards bodies). Our math is covered by automated tests, and every page shows when it was last reviewed. Learn more about how we verify our calculators →

Why SlickCalcs?