Calculators that show their work

Fabric Calculator

Estimate yards of fabric for identical rectangular pieces from bolt width, finished size, seam allowance, quantity and optional vertical pattern repeat.

Epoxy Calculator

Estimate mixed epoxy gallons from floor length, width, dry-film mils, coat count and waste, then split resin and hardener by your product's volume mix ratio.

Drywall Mud Calculator

Estimate ready-mix joint compound gallons and bucket count from 4×8 sheet count or room dimensions, using a planning rate for all tape coats plus waste.

Firewood Calculator

Measure a stacked woodpile and see how much of a 128 cubic foot cord it holds, a fair price at your per-cord rate, and whether the ticket matches the stack.

Electricity Cost Calculator

Work out what an appliance costs to run per day, month or year from its watts or amps, hours of use and your rate, with every state's EIA July 2026 price.

Square Footage Calculator

Calculate the square footage of a room or area from its measurements, with conversions to square meters, square yards, and acres, plus a cost estimate.

Pool Calculator

Find your pool's volume in gallons from its shape and dimensions, or work out how much salt to add to reach a saltwater chlorine generator's target level.

Box Fill Calculator

Count NEC 314.16 volume allowances for hots, neutrals, grounds, clamps and devices, then see which metal device or square boxes have enough cubic inches.

Stair Calculator

Calculate stair layout from total rise: riser count, riser height in carpenter fractions, tread run, stringer length, and angle: checked against IRC limits.

Concrete Calculator

Calculate how much concrete a slab, footing, wall, column, or post hole needs in cubic feet and cubic yards, plus how many 40, 50, 60, or 80 lb bags to buy.

Board Foot Calculator

Work out board feet for lumber from actual thickness, width, and length, with a rough-sawn quarter-thickness shortcut, waste allowance, and cost estimate.

Asphalt Calculator

Estimate tons of hot mix or recycled asphalt for a driveway, lot, or base repair from paved area and compacted depth, with an optional material cost estimate.

Topsoil Calculator

Work out cubic yards, weight, and bag count for a lawn, garden bed, or raised bed from its shape, area, and fill depth, with soil-texture density presets sourced from USDA soil science.

Conduit Fill Calculator

Check whether a set of THHN/THWN-2 conductors fits inside an EMT, IMC, RMC, or PVC conduit under the NEC Chapter 9 fill limits, and see the smallest size that would pass if it does not.

Engine Displacement Calculator

Find engine displacement in cc, liters and cubic inches from bore, stroke and cylinder count, plus compression ratio and mean piston speed if you know them.

Molarity Calculator

Convert between mass, molar mass, and volume to solve for molarity, grams of solute, solution volume, or molar mass, with compound values built in.

Temperature Converter

Convert between Celsius, Fahrenheit, and Kelvin instantly, with reference tables for oven temperatures, fever/body-temperature readings, and everyday weather values.

CD Calculator

Work out what a certificate of deposit will be worth at maturity: final balance, total interest, and the effective APY for any rate, compounding schedule, and term.

Mortgage Calculator

Estimate your monthly mortgage payment (principal, interest, taxes, insurance, PMI, HOA) and total interest, for any home price, down payment or rate.

Tip Calculator

Work out the tip and per-person total on a restaurant bill, with a toggle for tipping on the pre-tax subtotal vs. the tax-inclusive total and an even split across the table.

Markup Calculator

Solve for selling price, cost, or markup percentage from the other two, and see the corresponding margin percentage every time, since the two use different bases and are easy to mix up.

WACC Calculator

Calculate a company's weighted average cost of capital from its equity and debt weights, cost of equity (CAPM or a direct rate), and after-tax cost of debt.

SAT Score Calculator

Convert raw scores on a paper SAT practice test into scaled section scores and a 400–1600 total, using College Board’s official conversion table for Practice Test #4.

GPA Calculator

Calculate your unweighted or weighted GPA from letter grades and credit hours, using the standard 4.0-scale grade-point chart and the common Honors/AP weighting convention.

Words to Pages Calculator

Convert a word count into an estimated page count (or the reverse), based on font, size, and line spacing. Uses the standard 250-words-per-page, double-spaced convention as the baseline.

BMI Calculator

Calculate BMI from weight and height in US or metric units, see your CDC/WHO category and healthy-weight range, plus an optional Asian-population cutoff.

Calorie Calculator

Find your BMR, maintenance calories (TDEE), and a daily calorie target to lose, maintain, or gain weight, using the Mifflin-St Jeor equation.

Steps to Miles Calculator

Convert steps to miles or kilometers using a stride length estimated from your height and gender, not a flat 2,000-steps-per-mile guess. Also converts a distance back into steps.

Body Surface Area (BSA) Calculator

Calculate body surface area from height and weight using the Mosteller or Du Bois formula, in US or metric units, with both results shown side by side.

FFMI Calculator

Calculate your Fat-Free Mass Index and height-normalized FFMI from weight, height, and body fat percentage, and see how it compares to the documented natural (non-steroid) ceiling of 25.

Coin Flip Simulator & Probability Calculator

This coin flip simulator flips 1-500 virtual coins (fair or weighted) and shows the heads/tails split and longest streak, or use the probability calculator for exact binomial odds on any specific outcome.

Reaction Time Test

Test your simple reaction time over several trials, then compare your average, best, median, and consistency against reaction-time figures from published research.

Click Speed Test

Use this click speed test to check your clicks per second (CPS) and clicks per minute, then compare against the clinical single-finger tapping range from neuropsychology research.

Dice Roller & Probability Calculator

Roll 1-20 dice from d4 to d100 with a modifier, plus D&D 5th Edition advantage/disadvantage on a d20, or switch to the probability calculator for the exact odds of hitting any total.

Length Converter

Convert millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles, with reference tables for heights, tool sizes, and race distances.

Weight Converter

Convert between micrograms, milligrams, grams, kilograms, ounces, pounds, stone, and US tons instantly, with reference tables for body weight, cooking, and dosing.

Time Converter

Convert between seconds, minutes, hours, days, weeks, months, and years instantly, with reference tables and worked examples for ages, projects, and countdowns.

Volume Converter

Convert between teaspoons, tablespoons, fluid ounces, cups, pints, quarts, gallons, milliliters, and liters, plus kitchen and bottle-size reference tables.

Number Base Converter

Convert between binary, octal, decimal, and hexadecimal instantly, with a byte-value reference table and worked examples of the place-value math.

Electrical Converter (Watts, Amps, Volts)

Convert between watts, amps, and volts for DC, AC single-phase, and AC three-phase circuits, with power factor support and worked examples for household and industrial loads.

Percentage Calculator

Find a percentage of a number, calculate percentage increase or decrease, apply a discount, or compare two values with percent difference.

Fraction Calculator

Add, subtract, multiply, or divide two fractions (including mixed numbers), simplify a fraction to lowest terms, or convert between mixed numbers, improper fractions, decimals, and percents.

Shape Volume & Surface Area Calculator

This shape volume calculator finds the volume and surface area of a rectangular prism, cylinder, sphere, or cone. Enter dimensions in ft, in, yd, m, or cm and get both numbers at once.

Rounding Calculator

Round any number to a chosen number of decimal places or significant figures, with a choice of seven rounding methods including banker's rounding, and no binary floating-point rounding errors.

System of Equations Solver

Solve a system of 2 or 3 linear equations by Gaussian elimination, entered as ax + by = c (or ax + by + cz = d). Reports the exact solution, or whether it has none or infinitely many.

Date Calculator

Find the number of days between two dates, add or subtract days from a date, or count down to New Year's Day, Halloween, Thanksgiving, and Christmas.

World Clock & Time Zone Converter

See the current time in dozens of cities worldwide, or convert a specific date and time from one time zone to another, including the day-of-week shift and daylight-saving status.

Time Duration Calculator

Find the elapsed time between two clock times, add or subtract hours and minutes from a time, or calculate the duration between two full dates and times, with automatic overnight rollover.

Age Difference Calculator

Find the exact age gap between two people from their birth dates, in years/months/days and as a percentage of the older person's age, plus the "half your age plus seven" reference rule.

Keg Calculator

Work out how many 12 oz beers, US pints, or custom pours a keg holds for any standard US or metric keg size, plus how many kegs a party needs, using the federally defined keg sizes and standard-drink serving reference.

Pizza Calculator

Work out how many pizzas to order for a group of adults and kids, by appetite and pizza size, plus a slices-per-size reference chart and the reverse question: how many people one pizza feeds.

Rice to Water Ratio Calculator

Find how much water a given amount of dry rice needs, by type (white, brown, jasmine, basmati, arborio, wild rice, and more), using USA Rice's stovetop ratios, plus the estimated cooked yield.

Sentence Counter

Count sentences, words, and characters in text, plus reading time and Flesch readability scores, using Flesch's 1948 formula, its 1975 grade-level version, and Brysbaert's 2019 research.

Wingdings Translator

Convert text to Wingdings two different ways: a Unicode symbol preview that renders on any device, and the real Windows font code. Decode Wingdings-style text back into plain words too.

Words Per Minute (WPM) Average Calculator

Turn a word or character count, time taken, and error count into gross WPM, net WPM, and accuracy, then see it placed against published typing-speed research.

Line Counter

Count lines, non-empty lines, words, and characters in pasted text. Splits on CR, LF, or CRLF the way editors usually number rows.

Em Dash Copy Paste

Copy a real Unicode em dash (U+2014) plus en dash, figure dash, horizontal bar, and ASCII hyphen-minus in one click.

Prorated Rent Calculator

Work out the partial-month rent for a mid-month move-in or move-out, and compare what the three common day-count methods (actual days in the month, a flat 30-day "banker's month," and the rent divided across a 365-day year) would each charge for the same dates.

Dead Pixel Test

Check a monitor, laptop, or phone screen for dead, hot, and stuck pixels with a full-screen color test, plus a pixel-refresh flash mode for stuck sub-pixels.

Keyboard Test

Test every key on your keyboard with a live virtual layout, check how many keys register at once (rollover), and see which keys never registered.

Mouse Test

Test all five common mouse buttons (right-click included), measure your double-click interval against the default Windows setting, estimate the report rate, and count scroll ticks.

Touchscreen Test: Find Dead Zones

Touchscreen test: sweep a finger over a 12x18 grid to spot dead zones, press several fingers to see how many register, and watch a live log of every touch event.

Refresh Rate Test: Check Your Screen's Real Hz

Refresh rate test: measure the Hz your display is actually presenting at right now, with the frame-period spread and slow-frame count behind the number.

Scroll Test: Check Wheel Skips, Direction & Speed

Scroll test for mouse wheels and trackpads: count up/down ticks, flag oversized jumps that look like skips, and read delta mode and speed in this tab.

Sound Test: Left / Right Speaker Check in the Browser

Sound test for PC and phone speakers: play left-only, right-only, and stereo sine tones in this tab, then record Heard or Silent for each channel to spot a mute or swap.

MP3 Converter

Convert WAV, FLAC, Ogg, M4A, and MP3 to MP3 in the browser. Pick 128, 192, or 320 kbps, convert a batch, and download. Audio never leaves this device.

Golf Club Distance Chart

See typical yardage for every club in the bag by skill level, or enter your own driver distance to scale the whole chart to your swing, plus the yard gap between each club.