How thick should a shed slab be?

Four inches is common for a light storage shed. Workshops, compact tractors, masonry walls, or weak soils may require 5–6 inches, reinforcement, or an engineered thickened-edge foundation.

How much concrete is needed for a 10 by 12 shed slab?

At 4 inches thick, the slab contains 40 ft³, or 1.48 yd³ net. With 10% waste, the suggested order is about 1.63 yd³.

Does a shed slab need a footing?

It depends on shed size, wall construction, frost depth, soil, and local code. Some light sheds use a floating slab; larger or conditioned buildings may require thickened edges or frost-depth footings.

Shed Slab Calculator

Estimate concrete for a shed slab or outbuilding pad. Enter the formed dimensions and thickness to calculate cubic yards, bags, weight, waste, and ready-mix material cost.

Shed Slab Dimensions

Results update as you change the formed dimensions.

Length

Width

Slab thickness

Waste allowance

Ready-mix price

$/yd³

Order quantity

1.63yd³ with waste

Slab area

120ft²

Net volume

40ft³

Concrete weight

6,600lb · 3.3 tons

60 lb bags

98bags

80 lb bags

74bags

Estimated ready-mix material cost

$321

Includes $60 short-load fee when the order is under 3 yd³. Labor, base, forms, reinforcement, finishing, tax, and other delivery charges are excluded.

Shed Slab Concrete Thickness and Volume

A 4-inch slab is common for light storage sheds. Workshops, tractors, masonry walls, poor soils, or frost-sensitive construction can require thicker slabs, thickened edges, or footings.

This tool calculates the flat slab only. Thickened perimeter edges, frost footings, piers, and ramps should be calculated separately and added to the order.

How to Calculate Concrete for a Shed Slab

Multiply the formed length by width and slab thickness after converting thickness from inches to feet. Divide cubic feet by 27 for cubic yards, then add the selected waste allowance.

Rectangular slab order

yd³ = length (ft) × width (ft) × [thickness (in) ÷ 12] ÷ 27 × (1 + waste%)

Measure the inside of the forms. Calculate thickened edges, footings, ramps, and separate pads independently.

Shed Slab Planning Checklist

Confirm the slab footprint from the shed manufacturer or framing plan.
Check permit, setback, frost-depth, anchorage, and foundation requirements locally.
Add thickened edges, ramps, and equipment pads as separate volumes.
Prepare a compacted base and keep the finished slab above surrounding grade.