Free Online Construction Calculators
Work out square footage, gravel, concrete, roofing, stairs and air conditioner size for home projects.
Area and materials
Measure the space and order materials.
Square Footage Calculator
This square footage calculator works out the area of a room, floor, wall, patio or yard in square feet.
Gravel Calculator
This gravel calculator tells you how much gravel to order for a driveway, path, patio base or garden bed.
Concrete Calculator
This concrete calculator works out how much concrete you need for a slab, patio, sidewalk, footing or round column.
Building
Roofs, stairs and cooling.
Roofing Calculator
This roofing calculator estimates how much roofing material you need.
Stair Calculator
This stair calculator works out the layout of a straight staircase from the total rise, the height from one floor to the next.
BTU Calculator
This BTU calculator tells you what size air conditioner a room needs.
Free construction calculators
Start every project by measuring the area with the Square Footage Calculator, then order materials with the Gravel Calculator and Concrete Calculator. Estimates are a guide: check local building codes and ask your supplier.
Questions
Are these calculators free?
Yes, all of them, with no sign-up.
Which units do they use?
Feet and inches by default, with metric results where useful.
Should I order extra material?
Yes. Most jobs need 5% to 15% extra for waste.
Do these replace a contractor?
No. They give estimates; check codes and get quotes for large jobs.