Free calculators that just give you the number

Work out cubic yards of concrete and how many 60 lb or 80 lb bags a slab, footing or pad needs.

Convert a roof footprint and pitch into roofing squares, shingle bundles and underlayment rolls.

Count decking boards, linear feet and board feet for a deck, including the gap between boards.

Work out how many gallons of paint a room needs from its dimensions, coats and openings.

Count drywall sheets for a room, plus screws, joint tape and compound.

Turn room dimensions into boxes of tile or flooring, including a waste allowance for cuts.

Find the R-value your climate zone calls for and how many inches of a given insulation reach it.

Work out riser height, tread count and total run from a total rise, with IRC code checks.

Count posts, rails, pickets and concrete bags for a run of fence at any post spacing.

Convert a bed area and depth into cubic yards, bags and approximate tons of mulch, gravel, sand or topsoil.

Count pavers for a patio or walkway and estimate the bedding sand and gravel base beneath.

Count studs for a wall at 16 or 24 inches on centre, including corners, openings and plates.

Work out gutter sections, hangers and how many downspouts a roof area needs.

Convert kitchen cabinet runs into linear feet, countertop square footage and a rough budget.

Work out linear feet of baseboard for a room and how many stock lengths to buy.

Work out carpet in square yards for up to three room sections, with a waste allowance and a roll-width seam check.

Work out carpet for a straight flight from the step count, tread, riser and stair width.

Boxes of plank flooring plus underlayment, transition strips, and a check on how wide the final row lands.

Build up a flooring project cost from area and your own rates for material, fitting and removal.

Convert between millimetres, centimetres, metres, kilometres, inches, feet, yards and miles.

Convert between grams, kilograms, tonnes, ounces, pounds, stone and US tons.

Convert between millilitres, litres, teaspoons, cups, pints, quarts, gallons and cubic units.

Convert between Fahrenheit, Celsius and Kelvin, with all three shown at once.

Convert cups, tablespoons and millilitres to grams and ounces, using the density of the actual ingredient.

Convert between square feet, square metres, square yards, acres, hectares and square miles.

Convert between miles per hour, kilometres per hour, metres per second, feet per second and knots.

Convert between psi, bar, pascals, kilopascals, atmospheres and mercury column units.

Convert between US mpg, imperial mpg, litres per 100 km and kilometres per litre.

Convert between bytes, kilobytes, megabytes, gigabytes and their binary equivalents.

Add or subtract two durations in hours, minutes and seconds, with decimal hour totals.

Convert oven temperatures between Celsius, Fahrenheit and gas mark, with fan oven adjustments.

Convert a decimal to the nearest simple fraction, or a fraction to a decimal and percentage.

Convert numbers to Roman numerals and Roman numerals back to numbers, with a validity check.

Convert a value between metric prefixes, from pico through tera, for any SI unit.

Find a percentage of a number, work out what percentage one number is of another, or calculate percentage change.

Work out the tip, the total and the amount per person, with an option to round the total up.

Work out a sale price, the amount saved, and what stacked discounts really come to.

Calculate body mass index from height and weight in either metric or imperial units.

Work out an exact age in years, months and days from a birthdate, plus days until the next birthday.

Count the days, weeks, months and business days between any two dates.

Calculate a term GPA on the 4.0 scale, weighted by the credit hours of each course.

Estimate a monthly loan payment, total interest and total repaid from the amount, rate and term.

Add sales tax to a price, or work backwards from a tax-inclusive total to the pre-tax amount.

Convert a date and time between any two time zones, with daylight saving handled automatically.

Work out the concentration you get from a given vial size and diluent volume, and what one syringe mark is worth.

Convert a dose you already have into millilitres and syringe units at a known concentration.

Convert between grams, milligrams and micrograms, with an optional IU conversion using the potency from your own label.

Work backwards from a concentration you want to the amount of diluent that produces it.

Vial size, diluent volume and dose in one form — the syringe reading without doing two steps.

Multiply a per-kilogram figure from your own prescription by body weight, in either pounds or kilograms.

Lay a dose schedule you have been given onto calendar dates, so you can see what falls when.

What actually affects how long a reconstituted solution lasts, why sterility and potency are separate questions, and why no calculator can give you a date.

Enter your lifts, pick an animal, and find out what fraction of it you could theoretically fight. You cannot fight it.

Your lifts, lined up against every animal on the list at once. Sobering in one direction, encouraging in the other.

Ten questions of no diagnostic value whatsoever, scored out of 100.