Calculators
Free Online Calculators
33 free calculators and everyday tools for home projects, money and work. Each one runs in your browser, explains the math behind its answer and lists its sources. No sign-up and nothing to install.
Home improvement and construction calculators
Work out materials before you buy: paint, drywall, tile, lumber, gravel, roofing, decking and fencing, plus room sizes, stairs, pool volume and air conditioner size. Enter feet and inches or metric, add your own prices and get a shopping list.
Board Foot Calculator
Board feet for a lumber list in nominal or hardwood 4/4 sizes, board feet to linear feet, cubic meters, waste, cost and log scale.
BTU Calculator
Size a room air conditioner from square feet with the ENERGY STAR table, adjust for sun, people and kitchens, and see watts and tons.
Cubic Yard Calculator
Yards of dirt, topsoil, mulch, gravel, sand or concrete from length, width and depth in any units, plus bags, tons and cost.
Deck Calculator
Deck boards, screws, joists, beams and posts, footing concrete, railing and balusters, with a materials list and cost from your prices.
Drywall Calculator
How many sheets for walls and ceilings, with doors, windows, sheet sizes, waste, joint compound, tape, screws, corner bead and cost.
Fence Calculator
Posts, pickets, rails, panels, chain link or wire, post-hole concrete bags, gates and a materials list with cost from your prices.
Gravel Calculator
Cubic yards, tons and bags of gravel, crushed stone, pea gravel or sand for any area and depth, with compaction and cost.
Paint Calculator
Gallons or liters of paint for a room, walls, ceiling, accent wall or house exterior, with coats, primer, doors, windows, trim and cans.
Pool Volume Calculator
Gallons and liters for round, oval, kidney, L-shaped and sloped pools or hot tubs, plus fill time, pump turnover and dose math.
Roof Pitch Calculator
Convert pitch to degrees and slope, find rafter and hip lengths, use the pitch chart, or measure a roof from a photo or your phone.
Roofing Calculator
Roof area and squares from footprint and pitch, shingle bundles, underlayment, rafter length and a cost estimate. Nothing uploaded.
Square Footage Calculator
Square footage calculator for rooms, houses and lots of any shape. Add areas, subtract cut-outs, and get sq ft, m², sq yd and acres, plus flooring cost.
Stair Calculator
Risers, treads, total run, stringer length and layout, headroom and landings from your total rise, checked against the 2024 IRC.
Tile Calculator
Tiles laid out one by one in grid, offset, diagonal or herringbone, with boxes, grout and thinset.
Wallpaper Calculator
Rolls of wallpaper for a room, walls or an accent wall, strip by strip, with pattern repeat, half-drop, doors, windows and cost.
Money, pay and business calculators
Savings, debt, investing and pay: CD interest, credit card payoff, dividend income, FIRE targets, markup and margin, and overtime pay. They are educational tools that show their formulas and sources, not financial advice.
CD Calculator
A certificate of deposit’s maturity value, interest and APY, after-tax and real returns, CD ladders and early withdrawal penalties.
Credit Card Payoff Calculator
Months to pay off, the payment for a target date, minimum vs. fixed payments, avalanche vs. snowball and balance transfers.
Dividend Calculator
Dividend income, dividend yield and yield on cost, DRIP reinvestment growth year by year, and how much to invest for monthly income.
FIRE Calculator
Your FIRE number, years and age to financial independence, savings rate, and Lean, Fat, Barista and Coast FIRE targets.
Markup Calculator
Get selling price, markup, gross margin and profit from any two values, convert margin to markup, and test discounts and break-even.
Overtime Calculator
Time and a half and double time pay, a weekly timesheet with federal and California daily overtime, and salaried overtime.
Developer and security tools
Convert colors, generate UUIDs and create strong passwords. Everything is generated in your browser, so nothing you make is sent anywhere.
Hex to RGB Converter
Turn #rrggbb or 8-digit hex into rgb(), rgba(), HSL, OKLCH and more, convert whole lists and check WCAG contrast in your browser.
Strong Password Generator
Random passwords of any length, word passphrases and PINs, plus a strength checker. Runs in your browser; nothing is sent.
UUID Generator
Make v4, v7 and GUIDs, one or 10,000 at a time, then validate and decode any UUID. Runs in your browser; nothing is sent.
Writing and text tools
Count sentences and words, translate Morse code, and make small Unicode text you can paste anywhere.
Morse Code Translator
Text to Morse and Morse to text as you type. Hear it or flash a light, set WPM and Farnsworth, save a WAV, and use the full chart.
Sentence Counter
Count sentences, words, characters and paragraphs as you type, spot long sentences and check readability. Nothing is uploaded.
Small Text Generator
Type once and copy tiny small caps, superscript and subscript letters. Real Unicode characters, with missing letters flagged.
Tests, printables and classroom tools
Test your speakers and your reaction time, print graph paper at true scale, pick random letters and build seating charts.
Printable Graph Paper
1/4 in, 5 mm or custom squares, dot grid, isometric, polar, log and lined paper. Print at true scale or get a PDF.
Random Letter Generator
Pick 1 to 1,000 letters, vowels or consonants, with no repeats, a letter wheel, a classroom big display and other alphabets.
Reaction Time Test
Click, tap or press Space when the box turns green. Visual, sound and choice modes, average, median, history and charts.
Seating Chart Maker
Seating chart maker for classrooms, weddings and events. Paste names, drag them onto desks or tables, shuffle with rules, then print or save a PNG.
Spacebar Counter
How many times can you press Space in 5, 10, 30 or 60 seconds? Holding the key doesn’t count. Presses per second, bests and a chart.
Speaker Test
Check left and right audio, phase, bass and subwoofer, run a 20 Hz to 20 kHz sweep, play tones and noise. All sound is made in your browser.
Quick answers
The short version of the questions people ask most. Each calculator page has the full method, worked examples and sources.
How much paint do I need?
A gallon of paint covers about 400 sq ft per coat. A 12 × 12 ft room with 8 ft walls, one door and two windows has 340 sq ft of wall to paint, so two coats need 1.70 gallons: buy 2 gallons. Open the Paint Calculator.
How do I calculate square footage?
Measure the length and the width in feet and multiply them. A room 15 ft long and 12 ft wide is 15 × 12 = 180 square feet. Open the Square Footage Calculator.
How much gravel do I need?
Multiply the length by the width in feet, multiply by the depth in inches divided by 12, and divide by 27 to get cubic yards. A 54 by 12 foot driveway 4 inches deep is 216 cubic feet, or 8.00 cubic yards. Open the Gravel Calculator.
How many squares is my roof?
Divide the roof’s sloped surface area in square feet by 100. If you only know the footprint, multiply the plan area, overhangs included, by the pitch factor first. Open the Roofing Calculator.
How is overtime pay calculated?
Multiply your hourly rate by 1.5 to get the overtime rate, then multiply that by your overtime hours. At $20 an hour the overtime rate is $30.00, so 5 hours of overtime pays $150.00 and a 45-hour week pays $950.00 before taxes. Open the Overtime Calculator.
How do I calculate board feet?
Multiply the thickness in inches by the width in inches by the length in feet and divide by 12, then multiply by the number of pieces. A 2 × 6 that is 12 ft long is 2 × 6 × 12 ÷ 12 = 12 board feet. Open the Board Foot Calculator.
How these calculators are made
Every calculator is built and maintained by Raju, founder of MicroPlugins. The formulas follow published references, such as building codes, standards and government guidance, and each page links to the sources it uses and shows when it was last updated.
The math runs on your device, in your browser. What you type stays there, and there is no account to create. Found a mistake or want a calculator we don’t have yet? Tell us.
Looking for file tools instead? See all MicroPlugins tools, including the 3D viewers and converters, image tools and the screen recorder.