Estimate materials for a dozen home projects with the label’s own coverage rate: paint, primer, flooring, tile, drywall, insulation, siding, fencing, decking, gravel, sod, grass seed, countertops, and wallpaper — units rounded up with waste built in and a cost line for each.
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FORMULA USEDHome Project Materials Calculator
Coverage math, not guesswork
Every member of this family runs the same four-step pattern: measure the area (or let the tool do it from length × width), divide by the package’s label coverage, add the waste allowance, and round up — because nobody sells 0.9 of a box. The detail rows show the un-rounded number so you can sanity-check the round-up, and a cost line prices the order at your per-unit price.
The standard rates, named
Paint: 1 gal per 350–400 sq ft per coat (interior latex label standard). Primer: ~300 sq ft/gal (KILZ-style label). Drywall: 4×8 sheet = 32 sq ft. Insulation: R-13 roll, 15 in × 32 ft = 40 sq ft (Owens Corning standard). Siding: 1 square = 100 sq ft. Fence: posts max 8 ft on center; a 1×6 picket is really 5.5 in wide. Decking: a 5/4×6 board is 5.5 in wide — 16 ft of it covers 7.33 sq ft. Gravel: 1.4 tons per cubic yard. Sod: 9-sq-ft roll, 450-sq-ft pallet. Seed: 5 lb/1,000 sq ft new, 3 lb overseed. Wallpaper: 10 m × 53 cm roll ≈ 56 sq ft.
Worked example
Drywall an 8×10 room with 8-ft walls: 2 × (8 + 10) × 8 = 288 sq ft.
Fence, 100 ft with 5.5-in pickets and ½-in gaps: 1,200 ÷ 6 = 200 pickets.
Posts at 8 ft: ⌈100 ÷ 8⌉ = 13 sections, +1 corner post = 14 posts.
How to use it
Pick the material from the dropdown — the form adapts to it.
Enter your dimensions; the coverage field starts at the label standard, so edit it to match your product.
Check the waste allowance (10% is the default for most materials).
Read units to buy, the exact pre-roundup number, and the cost line.
Adjust the price field to your quote and the cost updates.
Frequently asked questions
Why does the calculator round up?
Stores sell whole gallons, boxes, sheets, and rolls. The rows show the exact figure before rounding — 288 sq ft of drywall is 9.9 sheets — and the headline shows what you actually buy: 10 sheets. Rounding down guarantees a second trip; rounding up guarantees leftovers for repairs, which for paint and flooring is a feature, not a bug.
How much paint do I really need for a 12×12 room?
Two coats over 144 sq ft is 288 sq ft of coverage; at the 350 sq ft/gal label rate that is 0.9 gal with a 10% allowance — one gallon finishes it. Buy a second if the walls are dark red, freshly textured, or you are painting over bare drywall, all of which drink more.
Why 10% waste on flooring, tile, and drywall?
Cuts at the borders, mistakes, damaged pieces, and future repairs. Straight-lay flooring and drywall are fine at 10%; diagonal tile patterns and herringbone need 15%+ because every border piece is cut at an angle. The waste field is editable for exactly this reason.
What is a square of siding?
Industry shorthand for 100 sq ft of wall area. Contractors quote siding by the square; a 1,200-sq-ft house needs 12 squares before waste. Boxes are labeled with the squares they cover — most vinyl boxes hold 1 or 2 squares — so match the coverage field to the box you are buying.
Why 1.4 tons of gravel per cubic yard?
A cubic yard of typical crushed stone weighs about 2,800 lb, i.e. 1.4 short tons. The calculator converts your area × depth into cubic yards, then into tons, and rounds the order up to the half-ton because that is how gravel yards sell it. For a compacted driveway base, order 10–20% more than the loose estimate.
Should I subtract doors and windows?
For siding and drywall, yes — measure the wall area as gross area minus openings (a standard door is ~21 sq ft, a window 10–15 sq ft). For paint and wallpaper, most pros keep the openings in the estimate as free waste allowance, since you will spend that paint cutting in around trim anyway.