Home Improvement Calculators
Measure once, then let these calculators turn your numbers into a shopping list. Enter the sizes in feet and inches and you get cubic yards of concrete with 60 lb and 80 lb bag counts, board feet of lumber with a price total, gallons of paint after doors and windows are taken out, wallpaper rolls that allow for the pattern repeat, tiles and full boxes with a waste allowance, and square yards of carpet on 12, 13.5 or 15 foot rolls with padding and installation cost.
Around the rest of the house, the BTU calculator sizes a window air conditioner or heater from the room, sun, insulation and climate, the fertilizer calculator reads the N-P-K numbers on the bag to tell you how many pounds and bags to spread, and the plant spacing calculator counts how many plants fit a bed in square or staggered rows. Each calculator runs in your browser, so it works on your phone in the store aisle, and the measurements you type are not sent to us. Treat every result as an estimate: round up, check the coverage printed on the product, and buy a little extra from the same batch so colors match.
9 free tools in this category. All run in your browser with no signup.
Concrete and lumber calculators
Get cubic yards of concrete for a slab, footing, column or set of steps, plus the number of 60 lb or 80 lb bags with 10% added for spillage. The lumber calculator totals board feet, linear feet and cost for 2x4s, 2x6s and custom sizes.
Paint and wallpaper calculators
Find how many gallons of paint a room needs for the walls, and the ceiling if you want it, after subtracting doors and windows. For wallpaper, pick a US or European roll size and enter the pattern repeat to get the number of rolls.
Air conditioner and heater size (BTU)
Size a window air conditioner or space heater from the room's floor area and ceiling height, then adjust for sun, insulation, climate, the number of people in the room and kitchen heat.
Tile and carpet calculators
Count tiles and boxes for a floor or wall with the waste percentage you choose, or get square yards of carpet with padding and installation cost. To switch between square feet, square yards and square meters, use the area converter.
Lawn and garden calculators
Turn the N-P-K label on a bag of fertilizer into pounds and bags for your lawn size, and work out how many plants fit a garden bed at the spacing on the seed packet.
Frequently asked questions
How many bags of concrete do I need for a 10x10 slab?
A 10 by 10 foot slab poured 4 inches thick holds about 33.3 cubic feet (1.23 cubic yards) of concrete. With 10% added for spillage and uneven ground, that comes to 62 bags of 80 lb mix or 82 bags of 60 lb mix, using typical yields of 0.60 and 0.45 cubic feet per bag. Check the yield printed on your bag, since it varies by brand and mix.
How much paint do I need for a 12x15 room?
With 8 foot ceilings the walls come to 432 square feet. Take out one door and two windows (about 51 square feet), paint two coats, and at 350 square feet per gallon you need about 2.2 gallons, so buy 2 gallons plus a quart. Add more for the ceiling, a dark color change or rough walls, and use the coverage figure on your can.
How much extra tile should I buy?
Plan on about 10% extra for a straight layout in a simple room, and more, often around 15%, for diagonal or herringbone patterns, rooms with many corners, or large tiles that leave big offcuts. The spare tiles cover cuts, breakage and future repairs, and buying them in the same order keeps the color and shade matched.
How do you calculate board feet?
Multiply the thickness in inches by the width in inches by the length in feet, then divide by 12, using the nominal size. An 8 foot 2x4 is 2 x 4 x 8 / 12 = 5.33 board feet. Lumberyards price hardwood by the board foot, while home centers usually price construction lumber by the piece.