Use these practical guides to measure rooms, estimate materials, plan costs, and avoid common project mistakes.
Measure each wall, multiply width by height, subtract large doors and windows, then multiply by the number of coats. Most interior repainting projects need two coats for an even finish. New drywall, very dark colours, porous surfaces, or dramatic colour changes may need primer or extra paint.
Always check the coverage number on the paint container. Coverage changes by brand, sheen, surface texture, roller type, and wall condition.
Concrete is ordered by volume. For slabs and patios, multiply length by width by depth. Convert inches to feet or centimetres to metres before calculating. Add a small waste allowance to reduce the risk of running short during the pour.
Depth has a major impact on volume. A small depth change across a large slab can add a lot of concrete.
For floors, multiply room length by width. For walls, multiply wall width by height. Break irregular spaces into rectangles and add them together. Add waste for cuts, breakage, layout changes, and pattern matching.
Buy full boxes and keep spare tiles for future repair. Matching shade batches later can be difficult.
Flooring projects need more than the basic room area. Add a waste allowance for cuts, damaged boards, angled walls, and layout direction. Include underlay, trims, thresholds, delivery, removal, and fitting when budgeting.
Compare products using the same unit, such as price per square foot or price per square metre.
Room area is only the starting point. Ceiling height, insulation, sunlight, people, and heat sources can increase or reduce BTU requirements. Oversized and undersized units can both create comfort and efficiency problems.
Use a calculator for early planning, but ask an HVAC professional for whole-home systems or difficult rooms.
Roofing estimates depend on roof area, pitch, complexity, waste, valleys, dormers, tear-off, and material type. Roofing squares are commonly used in the US, where one square equals 100 square feet.
Roofing is safety-sensitive work. Use the calculator for planning, not as a replacement for a contractor estimate.
