Square footage, flooring, roofing, AC sizing and wallpaper.
Good estimates prevent the two classic project headaches: running short on materials and overspending. This guide covers how to measure and estimate common home projects, with a calculator for each.
Most material estimates begin with area. For a rectangular room, multiply length by width; for odd shapes, split the space into rectangles and add the areas. Always add a waste factor — typically 10 percent for straight layouts and 15 percent or more for diagonal or patterned work — to cover cuts and mistakes.
Flooring is sold by the box, each covering a set area, so the job is converting your room's area (plus waste) into boxes, rounded up. The Flooring Calculator does this and estimates material cost. Buying from one batch helps color and lot consistency.
Roofing is measured in squares (100 square feet of roof surface), and because a roof is pitched, its surface is larger than the building's footprint — a pitch multiplier accounts for that. Shingles usually come three bundles per square. The Roofing Calculator estimates area, squares and bundles from your footprint, pitch and waste.
Sizing an air conditioner is about matching capacity to the room. A common rule is roughly 20 BTU per square foot, adjusted for sun exposure and occupancy, and 12,000 BTU equals one ton. The BTU / AC Size Calculator estimates the capacity a room needs. Bigger isn't better — an oversized unit short-cycles and dehumidifies poorly.
Wallpaper estimating has a twist: pattern repeats waste length on every strip, reducing usable strips per roll. The Wallpaper Calculator accounts for wall size, roll dimensions, pattern repeat and waste to give the number of rolls. As with flooring, order a little extra and from the same batch.
Measure twice, add the right waste factor, and round up — material is cheaper to buy once than to re-order mid-project. Keep in mind these figures cover materials only; underlayment, trim, fasteners and labor are extra. For complex or structural work, treat the estimate as a starting budget and confirm with a contractor.
About 10 percent for straight layouts, 15 percent or more for diagonal or patterned work.
100 square feet of roof surface; shingles usually come three bundles per square.
Roughly 20 BTU per square foot, adjusted for sun and occupancy; 12,000 BTU is one ton.
Pattern repeats waste length on each strip, lowering usable strips per roll.
No — they cover materials; trim, underlayment and labor are extra.