Every result on Calcupine comes from the formulas below. We publish them so you can check our work. All lengths are in feet unless marked in inches, and every quantity is rounded up to a whole unit you can buy.
Areas
Rooms and beds are built from sections. Each section is a rectangle (length × width), a triangle (½ × base × height) or a circle (3.1416 × radius²). Cut-out sections are subtracted. Feet and inches are combined as feet + inches ÷ 12.
Paint
| Step | Formula or figure |
|---|
| Wall area | 2 × (length + width) × height − 21 sq ft per door − 15 sq ft per window |
| Gallons | area × coats ÷ coverage (default 350 sq ft per gallon) |
| Ceiling | length × width, listed as separate ceiling paint |
| Primer | one coat over walls (and ceiling if chosen) |
| Buying | whole gallons; a leftover of 1/4 gallon or less becomes 1 quart, more becomes another gallon |
| Painter's tape | 2 × perimeter + 17 ft per door + 16 ft per window, in 180 ft rolls |
Concrete
| Step | Formula or figure |
|---|
| Slab | length × width × thickness (in) ÷ 12 |
| Footing | length × width (in) ÷ 12 × depth (in) ÷ 12 |
| Round hole | 3.1416 × (diameter (in) ÷ 24)² × depth (in) ÷ 12 × count |
| Waste | 10% by default |
| Bag yields | 80 lb = 0.60 cu ft, 60 lb = 0.45 cu ft, 40 lb = 0.30 cu ft |
| Ready-mix | cubic yards (cubic feet ÷ 27) rounded up to the next 1/4 yard; suggested from 1 cubic yard |
Tile
| Step | Formula or figure |
|---|
| Waste | straight 10%, diagonal 15%, herringbone 20%, or your own figure |
| Space per tile | (length + joint) × (width + joint) ÷ 144 sq ft |
| Grout | 144 × (L + W) × joint × thickness ÷ (L × W) cubic inches per sq ft, at 0.065 lb per cubic inch, plus 10% |
| Thinset (50 lb bag) | 95 sq ft (1/4 × 1/4 in notch), 70 sq ft (1/4 × 3/8 in), 45 sq ft (1/2 × 1/2 in) |
Flooring
| Step | Formula or figure |
|---|
| Waste | straight 10%, diagonal 15%, herringbone 20%, or your own figure |
| Boxes | area with waste ÷ square feet per box |
| Underlayment | area × 1.05 ÷ square feet per roll |
| Trim | length × 1.10 ÷ 8 ft pieces |
Mulch, soil, gravel and sand
| Step | Formula or figure |
|---|
| Volume | area × depth (in) ÷ 12 cubic feet; ÷ 27 for cubic yards |
| Default bags | mulch 2 cu ft, topsoil 0.75 cu ft, gravel and sand 0.5 cu ft |
| Weight | topsoil 1.1, gravel 1.4, sand 1.35 tons per cubic yard |
| Bulk | rounded up to the next 1/2 cubic yard or 1/2 ton |
Square footage and cubic yards
| Step | Formula or figure |
|---|
| Square yards | square feet ÷ 9 |
| Square meters | square feet × 0.0929 |
| Acres | square feet ÷ 43,560 |
| Cubic yards | area × depth (ft) ÷ 27 |
| Cubic meters | cubic feet × 0.0283 |
Drywall
| Step | Formula or figure |
|---|
| Board area | wall area (as for paint) + ceiling if chosen |
| Sheets | board area × (1 + waste, default 10%) ÷ 32, 40 or 48 sq ft |
| Screws | about 1 per sq ft of sheets bought |
| Joint compound | about 9 gallons per 1,000 sq ft, in 4.5 gallon buckets |
| Tape | about 380 ft per 1,000 sq ft, in 250 ft rolls |
| Corner bead | outside corners × wall height ÷ 8 ft, rounded up |
Wallpaper
| Step | Formula or figure |
|---|
| Strips | perimeter (in) ÷ roll width, rounded up, minus full strips over 36 in doors |
| Strip length | wall height + pattern repeat + 4 in |
| Strips per roll | roll length ÷ strip length, rounded down |
| Rolls | strips ÷ strips per roll, rounded up |
Fence and deck
| Step | Formula or figure |
|---|
| Posts | length ÷ spacing, rounded up, + 1 |
| Pickets | length (in) ÷ (picket width + gap), rounded up |
| Post concrete | hole volume minus a 3.5 in square post, + 10%, in 0.6 cu ft bags |
| Deck rows | deck width (in) ÷ (board width + gap), rounded up |
| Deck boards | rows × deck length × (1 + waste) ÷ board length |
| Joists and screws | length (in) ÷ spacing + 1; 2 screws per board per joist |
Roofing
| Step | Formula or figure |
|---|
| Roof area | (length + 2 × overhang) × (width + 2 × overhang) × √(1 + (pitch ÷ 12)²) |
| Waste | 10% gable, 15% hip |
| Bundles | 3 per square (100 sq ft) |
| Nails | 320 per square |
| Underlayment | roof area × 1.1 ÷ roll size |
Pavers, stairs and lawn
| Step | Formula or figure |
|---|
| Pavers | area × (1 + waste) ÷ paver area |
| Paver base | (area + edge length × depth) × depth; 1.4 tons per cubic yard |
| Bedding sand | area × depth, in 0.5 cu ft bags |
| Stair risers | total rise ÷ maximum riser (7 3/4 in), rounded up |
| Stair treads and run | risers − 1; treads × tread depth |
| Stringer | √(rise² + run²) |
| Sod | area × 1.05 ÷ piece size (2.67 sq ft slab) or pallet size |
| Grass seed | area ÷ 1,000 × seeding rate |
Prices
Shopping-list prices are rough US starting points so you can see a total. They are not quotes. Type your local prices into the list; your browser remembers them on that device only.
Limits
These are planning estimates. Products differ, so always check the coverage printed on what you buy. For structural concrete, follow local codes and an engineer's or contractor's specification.
Last reviewed: October 15, 2026.