Garage: Concrete Calculator Guide
Plan your garage floor in build order — base, rebar, concrete and cost for your footprint.
A garage floor carries concentrated wheel loads, so it's poured at least 4" (6" for heavy vehicles or a lift) and reinforced. Set your garage footprint and the steps size the base, rebar, concrete and cost for the pour.
Your garage size
This garage needs
7.82 yd³
≈ $3,168 – $6,912 installed
- 1
Measure & mark the area
Set your width and length above. Square off the corners and mark the perimeter. Not a simple rectangle? Work out the area with the square footage calculator first.
Square footage calculator - 2
Excavate & lay the gravel base
Dig down for the slab plus about 4" of base, then lay and compact crushed gravel so the slab drains and won't heave. This is the volume of base to order.
Gravel base calculator - 3
Set forms & add rebar
Build your forms to the finished height, then lay a two-way rebar or wire-mesh grid on chairs to control cracking. Here's the rebar to buy.
Rebar calculator - 4
Pour, screed & finish the concrete
Order or mix the concrete, pour into the forms, screed level, then float and finish. This is the concrete volume and bag count, with 10% waste built in.
Concrete slab calculator - 5
Budget the total cost
See what the finished slab costs — materials if you DIY, or fully installed by a contractor — for your exact size.
Garage slab cost
Typical garage sizes & cost
Volumes use standard bag yields and a 10% waste allowance; costs are national US averages that vary by region, mix and finish. See our methodology for exactly how each figure is worked out, or check the reference sources: