Concrete Slab Calculator
Pouring a pad for a shed, grill, hot tub or fire pit? Enter the slab dimensions to get the concrete volume in cubic yards and the number of bags — with a little extra built into the guidance.
Concrete Slab Calculator
Why use the Concrete Slab Calculator
Come up short mid-pour and the slab sets with a weak cold joint. This gets the concrete amount right.
How to get your numbers
- Slab length & width in feet.
- Thickness in inches (4 is standard for patios).
- Order about 10% extra.
Recommended for this job
How to use it
- Enter the slab length and width in feet.
- Enter the thickness in inches (4 inches is standard for patios).
- Order about 10% extra, and consider ready-mix delivery above ~1 cubic yard.
Frequently asked questions
How much concrete do I need?
Multiply length × width × thickness (in feet) for cubic feet, then divide by 27 for cubic yards. A 10×10 slab at 4 inches is about 1.2 cubic yards.
How many bags of concrete are in a cubic yard?
About 60 bags of 60 lb or 45 bags of 80 lb — which is why bulk delivery wins on anything larger than a small pour.
How thick should a concrete slab be?
Four inches suits patios and sheds; go to 5–6 inches for heavy loads like a hot tub or vehicle, and add rebar or wire mesh.
How much concrete for a 10×10 slab?
About 1.2 cubic yards at 4 inches thick — roughly 74 sixty-lb bags or 56 eighty-lb bags. Order about 10% extra.
Do I need rebar in a concrete slab?
For heavy loads or large slabs, yes — rebar or wire mesh controls cracking. Small, lightly loaded pads can often use fiber-reinforced mix.
Should I use ready-mix or bagged concrete?
Bagged is convenient for small jobs; ready-mix delivery is usually cheaper and easier above about one cubic yard.
How long does concrete take to cure?
It is walkable in 24–48 hours and reaches most of its strength in about 7 days, with full cure at 28 days. Keep it moist while curing.
