How much concrete for a 10x12 shed slab?
1.5 cu yd of concrete for a 10x12 shed slab, at the settings most people start with. Below the calculator are the same numbers for the alternatives you are likely to choose, and what each one does to the total.
Reviewed · Method: measured dimensions, industry coverage rates, rounded up to real package sizes · How the numbers are calculated
Values are pre-filled for this page. Change anything and hit Recalculate.
The answer, and what it is made of
A 12 x 10 ft slab at 4 in thick is 1.5 cu yd of concrete. That is 70 bags at 80 lb each, which is why this size usually goes ready-mix: 70 bags is a long day with a mixer, and the truck arrives at a consistent slump instead of however you happened to mix the fortieth bag.
Planning figure for everything on that list: $521 to $863, with $670 as the realistic middle for the products most people actually buy. These are estimates for budgeting, not quotes. Prices move by region and by season, and the middle figure assumes a mid-range product rather than the cheapest thing on the shelf.
Thickness is the expensive variable: 1.5 cu yd at 4 in becomes 2.2 cu yd at 6 in, a jump of 47%. That extra concrete does less for crack resistance than a properly compacted base, which costs a fraction as much.
What changes if you change one thing
| Change the slab thickness | You buy |
|---|---|
| 4 in slab, the usual for a shed | 1.5 cu yd |
| 5 in slab, heavy mower or lathe | 1.9 cu yd |
| 6 in slab, vehicle or lift | 2.2 cu yd |
Every row is a live calculation, not an estimate. The shaded row is what this page defaults to.
What goes in the cart
| Item | Quantity |
|---|---|
| Concrete mix, 80 lb | 70 bags |
| Concrete mix, 60 lb (alternative) | 94 bags |
| Crushed gravel base | 2.1 tons (40 cu ft) |
| 6 mil vapor barrier | 120 sq ft |
| Form boards + stakes | 44 ft |
| Control joints | 2 runs |
Above 1 cubic yard, call the truck. 70 bags is 5,600 lb to haul and mix before it sets. A short-load fee beats a failed pour.
What this size actually changes
Forty cubic feet is right at the awkward boundary: 70 bags of 80 lb is too much for one person in a day, and 1.5 cubic yards is under most ready-mix minimums, which usually sit at 1 or 2 yards with a short-load charge below that. On a slab this size the delivery fee often costs more than the concrete, so many people buy bags and accept the labour.
Figure. 10x12 shed slab at 4 in thick over a compacted base. Thickness sets the volume; the base sets whether it cracks.
How the quantity is worked out
Concrete is ordered by the cubic yard and sold in bags by weight, and the gap between those two units is where most estimates go wrong. A yard is 27 cubic feet, so a 10x12 slab at 4 in thick is 40 cu ft, or 1.5 cu yd. Rounded to whole yards at the ready-mix plant, that is 1.5 or 2 — and the shortfall shows up as a slab that is an inch thin at one corner.
Thickness is the expensive variable. Going from 4 in to 5 in on the same footprint adds 25 percent to the volume and 25 percent to the bill. Depth of the compacted base is the cheap variable: a proper 4 to 6 in base costs far less than an extra inch of concrete and prevents most of the cracking that a thicker slab would not have fixed anyway.
How to measure this job
Measure the shed footprint and then add the overhang. A slab for a 10x12 shed is normally poured at 11x13 so the frame sits fully on concrete and the edges can be trowelled clean. If the shed is a kit with a stated base size, use that number — kit manufacturers size the base to the frame, not to the floor area.
Then measure the drop from the intended slab level to the ground. A slab that finishes more than about 8 in above grade needs the edges built up and compacted, or the concrete will run out under the formwork. Set the formwork with a level across the diagonals before ordering concrete — a slab that is out of square is a shed that never sits flat.
Mistakes that cost real money
Ordering exactly the calculated volume
Ready-mix is delivered in whole yards and you cannot add half a yard on site. Order 5 to 10 percent over, because spillage, an uneven subgrade and a slightly deeper edge all consume concrete. Running short mid-pour produces a cold joint, which is a permanent weak line.
Pouring the slab before the base is compacted
A shed slab carries a static load, so it does not need to be thick, it needs to be even. Four inches over loose fill cracks under its own weight. Compact in 4 in layers with a plate, and check the level again afterwards, because compaction moves the surface.
Pouring 1.5 yards in one go without help
Forty cubic feet placed and screeded is a two-person job at minimum, and a third person on the float makes it easier. Concrete does not wait: once it is out of the truck or the mixer you have about an hour before it stops being workable.
Setting the slab level below the surrounding ground
A shed slab should finish at least 2 in above grade with the ground falling away from it. A slab flush with the soil holds water at the edges all winter, and the bottom of the timber frame sits in it.
Frequently asked questions
How many 80 lb bags of concrete make a yard?
Forty-five. An 80 lb bag yields about 0.6 cu ft, and a cubic yard is 27 cu ft. That means a 1.5 cu yd slab needs roughly 68 bags, which is why anything past about one yard usually goes ready-mix: 68 bags is a long day with a mixer and a lot of lifting.
How thick should a shed slab be?
Four inches over 4 in of compacted base is standard for a garden shed, and it will carry a ride-on mower. Five inches if you keep a trailer or heavy equipment inside. Thickness beyond that buys very little; a flat, well-drained base buys a lot.
Is 1.5 cubic yards enough for a 10x12 shed slab?
At 4 in thick, yes, with a little to spare. Order 1.6 to 1.7 yards, or 72 to 76 bags, because the subgrade is never perfectly flat and a low corner eats the margin. Running short mid-pour creates a cold joint.
Can I pour a shed slab in two halves?
You can, but the joint between them is a permanent weak line and it will show. If you must, pour against a keyed edge or use a construction joint with dowels. On 40 cu ft, one pour with two people is far better than two pours with one.
What will the materials for this cost?
A planning range of $521 to $863 for everything in the shopping list, with $670 as the realistic middle. That is materials only: it excludes labour, delivery, tool hire and disposal of the old surface. Treat it as a budgeting figure, not a quote.