Dry Pour Concrete Calculator
Size a dry-pour (pour-and-soak) concrete slab — enter your slab dimensions to get the number of 40, 60 or 80 lb bags you need to spread dry and then wet, plus an estimated cost.
What is dry pour concrete?
Dry pour — also called pour-and-soak — skips mixing: you spread dry concrete mix into a form, screed it level, then wet it down with a fine mist so it hydrates and sets in place. It's a popular DIY shortcut for small, light-duty slabs like garden pads, shed floors, walkways and stepping stones. Because it's based on the same volume as a normal pour, the bag count is the same — the calculator above sizes it from your slab dimensions.
bags = (length × width × thickness ÷ 12, in cu ft) ÷ bag yield
How to dry pour a slab
- Build and level a form, and compact the subgrade.
- Spread the dry mix and screed it to your thickness (most DIY slabs are 2–4 inches).
- Mist the surface evenly with a fine spray — soak it through without washing channels in it.
- Keep it damp while it cures over the next few days.
Dry pour works for non-structural slabs, but it generally reaches lower strength and cures less evenly than properly mixed concrete, so keep it to light-duty projects. For load-bearing work or a precise cost comparison, use the concrete calculator and the concrete cost calculator.
Frequently asked questions
What is dry pour concrete?
Dry pour (also called pour-and-soak) is a method where you spread dry concrete mix into a form, screed it level, and then wet it down with a fine mist so it hydrates and sets in place — skipping the usual mixing. It is popular for small DIY pads, walkways and stepping stones.
How many bags do I need for a dry pour slab?
The bag count is the same as a normal pour, since it is based on volume: spread enough dry mix to fill the form to your thickness. Using the standard yields (80 lb ≈ 0.60 cu ft, 60 lb ≈ 0.45, 40 lb ≈ 0.30), the calculator works out how many bags to buy for your slab size.
Does dry pour concrete actually work?
Dry pour can work for light-duty, non-structural slabs like garden pads, shed floors and walkways, but it generally reaches lower strength and more uneven curing than properly mixed concrete. For anything load-bearing or structural, mixed concrete is the reliable choice. Treat dry pour as a convenience method for small projects.
How thick should a dry pour slab be?
Most DIY dry-pour slabs are poured 2 to 4 inches thick. Thicker slabs are harder to wet all the way through, which is a common dry-pour failure point. The calculator lets you set the thickness so the bag count matches your plan.