17 calculators, in imperial and metric
Construction calculators for home projects
Enter your measurements and get the concrete, gravel, tile or roofing to buy, with bag and box counts and the formula behind every result.
Every calculator shows its working
Pick a calculator, type your sizes and read what to buy. Each result shows the rounded purchase, the exact figure and the formula, in feet or metres. See all 17 calculators
- FlTile12 × 10 ft floor130 tiles
- CoConcrete10 × 10 ft slab, 4 in1.36 yd³
- CoConcrete slab12 × 12 ft, 4 in88 bags
- CoConcrete bags6 × 4 ft pad15 bags
- CoCubic yards10 × 10 ft, 6 in1.85 yd³
- LaGravel20 × 10 ft path, 3 in2.04 yd³
- LaGravel driveway50 × 10 ft, three layers24.1 tons
- LaMulch20 × 4 ft bed, 3 in11 bags
- LaTopsoil20 × 10 ft, 4 in2.72 yd³
- FlShower tileThree walls to 84 in82 tiles
- RoRoof pitchRise 6 in a run of 1226.57°
- RoRoof area40 × 30 ft at 6/1216.5 squares
- CaBoard and batten12 ft wall, 16 in gaps8 battens
17 calculators in five trades
Each with its formula and a worked example.
Concrete calculators
- Concrete Calculatoryd³, m³, bags
- Concrete Slab Calculatorslabs
- Concrete Bag Calculatorbags
- Cubic Yard Calculatoryd³, ft³, m³
Landscaping calculators
- Gravel Calculatortons, yd³
- Pea Gravel Calculatorbags, tons
- Gravel Driveway Calculatorlayers
- Mulch Calculatoryd³, bags
- Topsoil Calculatoryd³, tons
Flooring and tile calculators
- Tile Calculatortiles, boxes
- Shower Tile Calculatorwalls
- Flooring Waste Calculatorboxes
- Grout Calculatorlb, kg
Roofing calculators
- Roof Pitch CalculatorX/12, degrees
- Roof Area Calculatorsquares
Carpentry calculators
- Board Foot Calculatorboard feet
- Board and Batten Calculatorspacing
The formula behind each calculator, tested in code
Every page shows its formula, a worked example and its assumptions. The same functions run in 135 automated tests before each release.
- Exact unit conversions1 in = 25.4 mm
- Bag yields and densities you can edityour product
- Results always rounded upwhole bags
volume V = length × width × thickness
order V × (1 + waste ÷ 100)
bags ⌈ order ÷ yield per bag ⌉
example 10 × 10 × 0.333 ft = 33.33 ft³
+ 10 % = 36.67 ft³ = 1.36 yd³
36.67 ÷ 0.60 ft³ = 61.1 → 62 bags
✓ 135 tests passed · units, rounding, invalid input
How accurate is each calculator?
The maths is exact. The result is only as good as your measurements and the bag yield or density you enter, so measure twice.
How much extra should I order?
Each calculator suggests an allowance: 5 to 10 % for concrete, about 10 % for straight tile, 15 % for showers and diagonal layouts.
How many 80 lb bags make a cubic yard?
About 45, at the common yield of 0.60 ft³ a bag. Check the yield printed on your product.
Can a calculator size my footing or slab?
No. It works out quantities. Thickness and reinforcement come from your plans, an engineer and your local building code.
Is it free, and is my data stored?
It is free and needs no account. Calculations run in your browser and nothing you type is sent to us.