How much concrete is a 40×80 slab?
A 40-by-80-foot slab covers 3200 square feet. At the standard 4-inch thickness that's about 39.51 cubic yards of concrete before waste, or roughly 43.46 yards once you add a 10% allowance. At about 43.46 cubic yards you are into multi-truck territory, so line up site access and timing before you schedule delivery. The calculator above is pre-filled to these dimensions; change the thickness or price to match your job.
Concrete for a 40×80 slab by thickness
| Thickness | Concrete to order | 80 lb bags | Material cost |
|---|---|---|---|
| 4″ (standard) | 43.46 yd³ | 1,956 | $6,953 |
| 5″ | 54.32 yd³ | 2,445 | $8,691 |
| 6″ | 65.19 yd³ | 2,934 | $10,430 |
Material cost at $160/yd³ ready-mix, before delivery fees. Cost data updated June 2026.
Planning a 40 × 80 slab delivery
This is a 3,200-square-foot pour: at 4 inches with 10% waste, the planning quantity is 43.46 cubic yards, equivalent to 1,956 standard 80 lb bags. Bag mixing is a substantial handling job at this scale. Give the ready-mix supplier your quantity, access constraints, and placement method so they can plan truck sizes and delivery intervals.
The 4-inch setting is a calculator starting point, not a structural recommendation for a shop or building. Use your project's specified thickness, and account separately for thickened edges and footings. Review the slab preparation guide before scheduling the pour.
Common questions
How many yards of concrete for a 40x80 slab?
A 40x80 slab at 4 inches thick needs about 39.51 cubic yards before waste. Add 5-10% extra so you don't come up short. Change the thickness in the calculator above to see how it affects the total.
How many bags of concrete for a 40x80 slab?
At 4 inches thick that's roughly 1956 eighty-pound bags with a 10% allowance. Past about 1 cubic yard (around 45 bags), ready-mix delivery is usually cheaper and far less work than mixing bags by hand.
What does a 40x80 slab cost?
Material alone is a small share of the total. Installed, slabs this size run a wide range depending on thickness, finish, site prep, and region. Use the calculator's installed-cost range as a ballpark, then compare local quotes for a real price.