Home project calculators

Pick a project. Each calculator explains its formula, lists its assumptions and links to its sources.

• Concrete Slab Calculator

  Estimate the concrete for a rectangular slab in cubic yards and in 40, 50, 60, 80 or 90 lb bags, with a waste allowance.

  Assumes: The slab is a rectangle with the same thickness everywhere.

• Paint Calculator

  Work out how much paint a room needs from its size, doors, windows, number of coats and the coverage printed on the can.

  Assumes: The room is rectangular with a flat ceiling.

• Mulch Calculator

  Estimate mulch for a rectangular or round bed in cubic yards and bags, and compare the cost of bulk delivery with bagged mulch.

  Assumes: The bed is a rectangle or a circle with an even depth.

• Gravel and Stone Calculator

  Estimate how many cubic yards and how many tons of gravel, crushed stone or sand you need for an area and a depth, with typical weights by material.

  Assumes: The area is a rectangle with an even depth.

• Tile Calculator

  Work out how many tiles and boxes you need for a floor or wall from its size, the tile size, the grout joint and a waste allowance.

  Assumes: The area is a rectangle; use "Area not tiled" for tubs, islands and anything you will not tile.

• Roofing Shingle Calculator

  Estimate the roof area, roofing squares and bundles of shingles from the roof footprint and its pitch, with an allowance for cuts and waste.

  Assumes: Every slope of the roof has the same pitch. For roofs with different pitches, calculate each part separately and add it as extra area.

• Fence Calculator

  Estimate the posts, sections, rails and pickets for a fence from its length, post spacing, gates and picket size.

  Assumes: The fence is a straight line. For corners, calculate each straight run separately and subtract one post for every shared corner.

• Sod Calculator

  Work out how many square feet, rolls or slabs and pallets of sod you need for a lawn, with an allowance for cuts and waste.

  Assumes: The lawn is a rectangle; subtract patios, paths and beds in "Area without sod", or split an irregular lawn into rectangles and add the results.

• Square Footage Calculator

  Find the area of a rectangle, triangle, circle or trapezoid in square feet, square yards, square meters and square inches, from measurements in feet, inches, yards, meters or centimeters.

  Assumes: Shapes are flat and measured straight across. For an L-shaped or irregular area, split it into rectangles, triangles and circles and add the results.

• Deck Calculator

  Estimate the deck boards, joists and fasteners for a rectangular deck from its size, the board width and gap, the joist spacing and an allowance for waste.

  Assumes: The deck is a rectangle. The boards run along the length and the joists run across the width, so every board crosses every joist once.