Free calculators & tools
No signup. No watermarks. Just instant answers for finance, health, and business.
Tip: use your keyboard. Enter = evaluate, Esc = clear.
Business ›
Invoice Generator
Create professional invoices for free. Fill the form, preview live, and download a clean PDF. No watermarks on…
OpenMarkup Calculator
Free markup calculator. Set a selling price from cost and markup %, or back out the markup. Always shows gross…
OpenROI Calculator
Free ROI calculator. Compute return on investment and annualized CAGR for any investment, with optional recurr…
OpenFreelance Hourly Rate Calculator
Free freelance hourly rate calculator. Work out the minimum rate to hit your income target after expenses, tax…
OpenWord Counter
Free word and character counter. Count words, characters (with/without spaces), sentences, paragraphs, and rea…
OpenHex to RGB Color Converter
Free hex to RGB color converter. Convert between #RRGGBB hex codes and RGB values with a live color swatch. No…
OpenFile Size & Download Time Calculator
Free file size and download time calculator. Convert bytes, KB, MB, GB, TB and estimate download time at your …
OpenBusiness Days Calculator
Free business days calculator. Add business days to a date or count weekdays between two dates. Skips weekends…
OpenCap Rate Calculator
Free cap rate calculator. Compute the capitalization rate for a rental property from net operating income and …
OpenLate Payment Interest Calculator
Free late payment interest calculator. Work out interest on an overdue invoice or debt by days and annual rate…
OpenPayback Period Calculator
Free payback period calculator. See how long an investment takes to recoup its cost from annual savings or cas…
OpenTime Zone Converter
Free time zone converter. Compare current times across three zones and find the working-hours overlap for a me…
OpenPassword Strength Checker
Free password strength checker. Score any password by entropy and estimated crack time. Runs entirely in your …
OpenMarkdown to HTML Converter
Free Markdown to HTML converter. Turn headings, bold, lists, links, and code into clean HTML for paste into a …
OpenPomodoro Timer
Free Pomodoro timer. 25-minute focus blocks with 5-minute breaks to beat procrastination. Runs in your browser…
OpenFinance ›
Auto Loan Calculator
Free car loan calculator with amortization schedule and extra payment support. See total interest, payoff date…
OpenSales Tax Calculator
Free sales tax calculator. Add tax to a price or back it out of a total. US state sales tax rates built in. No…
OpenSalary to Hourly Converter
Free salary-to-hourly converter. Turn an annual salary into hourly, weekly, and monthly pay, adjusted for hour…
OpenLease vs. Buy Calculator
Compare leasing vs. buying a car over the same ownership window. Total cost of each, breakeven year, and which…
OpenChild Support Calculator
Free child support estimate using a simplified income-shares guideline. Enter both parents' incomes, custody n…
OpenRetirement Calculator
Free retirement calculator. Project how current savings and monthly contributions grow to retirement age, with…
OpenCredit Card Payoff Calculator
Free credit card payoff calculator. Model snowball or avalanche payoff for multiple cards and see your debt-fr…
OpenRefinance Calculator
Free refinance calculator. Compare your current loan against a new rate and term, see monthly savings, break-e…
OpenCost of Living Calculator
Free cost of living calculator. Compare monthly expenses between two cities and find the equivalent salary nee…
OpenNet Worth Calculator
Free net worth calculator. Add your assets and liabilities to get your net worth instantly, with an asset-to-l…
OpenSimple Loan Calculator
Free simple loan calculator. Get the monthly payment, total interest, and payoff impact of extra payments for …
OpenInvestment Calculator
Free investment calculator. Project how a lump sum plus monthly contributions grow over time, with CAGR and in…
OpenMortgage Payoff Calculator
Free mortgage payoff accelerator. See how extra monthly payments shorten your term and save interest. Payoff d…
OpenTip Calculator
Free tip calculator. Work out the tip amount, total, and per-person share for any bill, by percentage or flat …
OpenStacked Discount Calculator
Free stacked discount calculator. Apply up to three sequential discounts to a price and see the true final tot…
OpenHealth & Fitness ›
TDEE Calculator
Free TDEE calculator. Calculate total daily energy expenditure and macros for weight loss, maintenance, or mus…
OpenBMI Calculator
Free BMI calculator. Enter weight and height (imperial or metric) for instant BMI and WHO category with a visu…
OpenBMR Calculator
Free BMR calculator. Mifflin-St Jeor or Harris-Benedict, imperial or metric. Find resting calories burned per …
OpenMacro Calculator
Free macro calculator. Split a daily calorie target into protein, fat, and carb grams for balanced, low-carb, …
OpenHeart Rate Zones Calculator
Free heart rate training zone calculator. Get Karvonen or max-HR percentage zones by age and resting heart rat…
OpenPregnancy Due Date Calculator
Free pregnancy due date calculator. Estimate your due date (EDD) from your last menstrual period, with current…
OpenBody Fat Calculator
Free body fat calculator using the US Navy circumference method. Estimate body fat %, fat mass, and lean mass …
OpenWaist to Hip Ratio Calculator
Free waist-to-hip ratio calculator. Compute WHR and check it against WHO risk bands for men and women. No sign…
OpenRunning Pace Calculator
Free running pace calculator. Convert distance and time to pace per km or mile, or work out finish time from a…
OpenOne Rep Max Calculator
Free one-rep max calculator. Estimate your 1RM from any set with Epley and Brzycki formulas, plus working-set …
OpenSleep Cycle Calculator
Free sleep cycle calculator. Find the best bedtime for any wake time using 90-minute sleep cycles. Wake refres…
OpenWater Intake Calculator
Free water intake calculator. Estimate daily water needs from body weight, exercise, and climate in liters, cu…
OpenOvulation Calculator
Free ovulation calculator. Estimate your ovulation day and fertile window from your last period and cycle leng…
OpenPregnancy Weight Gain Calculator
Free pregnancy weight gain calculator. See recommended IOM weight-gain ranges by pre-pregnancy BMI and your cu…
OpenBAC Calculator
Free blood alcohol content (BAC) estimator using the Widmark formula. Educational estimate by weight, drinks, …
OpenHome & Construction ›
Roofing Cost Calculator
Estimate roofing replacement cost by square footage, material, and pitch. Asphalt, metal, and tile. Quote PDF …
OpenConcrete Calculator
Free concrete calculator. Estimate cubic yards for slabs, footings, columns, and walls, plus 60/80 lb bags and…
OpenLumber Calculator
Free lumber board foot calculator. Work out board feet and total cost for any thickness, width, and length. Co…
OpenMulch, Soil, Rock & Gravel Calculator
Free bulk material calculator for mulch, soil, sand, gravel, and rock. Get cubic feet, cubic yards, liters, ap…
OpenDrywall Calculator
Free drywall calculator. Estimate how many 4x8 or 4x12 drywall sheets you need for any room, with openings and…
OpenLighting Calculator
Free lighting calculator. Get recommended lumens and bulb count for any room by size, type, and ceiling height…
OpenPaint Calculator
Free paint calculator. Estimate gallons and liters of paint for walls and ceilings from room dimensions, coats…
OpenRoof Pitch Calculator
Free roof pitch calculator. Convert roof rise and run into pitch (x/12), angle degrees, grade %, and slope fac…
OpenWallpaper Calculator
Free wallpaper calculator. Estimate how many wallpaper rolls you need by room size and pattern repeat. No sign…
OpenSiding Cost Calculator
Free siding cost calculator. Estimate material cost to side a house by vinyl, fiber cement, wood, or metal. No…
OpenCarpet & Flooring Calculator
Free carpet and flooring calculator. Estimate square feet, square yards, and material cost for any room, with …
OpenDeck Cost Calculator
Free deck cost calculator. Estimate decking, framing, and total material cost for wood, composite, or hardwood…
OpenInsulation R-Value Calculator
Free insulation R-value calculator. Total R-value from layers, plus U-factor and rough heat loss. No signup.
OpenMath ›
Basic Calculator
Free online calculator for quick math. Add, subtract, multiply, divide, percentages. Use keyboard or click. No…
OpenUnit Converter
Free unit converter for length, weight, temperature, volume, speed, and digital storage. Instant, accurate, no…
OpenPythagorean Theorem Calculator
Free Pythagorean theorem calculator. Find the hypotenuse or either leg of a right triangle. See formula work a…
OpenPercentage Calculator
Free percentage calculator. Find X% of Y, what percent X is of Y, or the percent change between two values. In…
OpenQuadratic Equation Solver
Free quadratic equation solver. Find real and complex roots of ax² + bx + c = 0 with the quadratic formula and…
OpenMean, Median, Mode & Standard Deviation Calculator
Free statistics calculator. Enter a list of numbers for the mean, median, mode, range, sum, and both sample an…
OpenScientific Notation Converter
Free scientific notation converter. Convert between decimal form and scientific notation (a × 10ⁿ) instantly, …
OpenRatio Calculator
Free ratio calculator. Simplify any ratio (6:8 → 3:4) and solve missing values when scaling ratios. Instant, n…
OpenLCM and GCD Calculator
Free LCM and GCD calculator. Find the least common multiple and greatest common divisor of two or three number…
OpenLogarithm Calculator
Free logarithm calculator. Compute log base b of any number, plus natural log and base-10 log. Works with any …
OpenRoman Numeral Converter
Free Roman numeral converter. Convert numbers to Roman numerals and back (1999 → MCMXCIX). Validates subtracti…
OpenNumber Base Converter
Free number base converter. Convert between binary, octal, decimal, and hexadecimal instantly. Perfect for pro…
OpenAge Calculator
Free age calculator. Find your exact age in years, months, and days, days lived, and days until your next birt…
OpenRandom Number Generator
Free random number generator. Pick random integers in any range, with unique or repeatable options. Instant, n…
OpenFactorial, Permutation & Combination Calculator
Free factorial, permutation, and combination calculator. Compute n!, P(n,r), and C(n,r) with big-number suppor…
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