Concrete Calculator

Calculate slabs, footings, walls, columns, and circular pads in US or metric units—with transparent bag yields and allowance.

Five common shapes
Ready-mix and bag totals
50, 60, and 80 lb bags

Project calculator

Concrete Calculator

Estimate concrete volume, ready-mix yards, bags, and cost.

Methodology

From dimensions to bags

Calculate shape volume

Rectangular pours use length × width × thickness. Round pours use π × radius² × depth.

Multiply the quantity

Identical footings, pads, or columns are combined before the planning allowance is applied.

Add an allowance

The default 10% follows Sakrete’s planning guidance for uneven bases, spillage, and jobsite variation.

Round to whole bags

Recommended volume is divided by the selected product yield and rounded up to the next whole bag.

Worked example

A 10 × 6 ft slab, 4 inches thick

20 ft³exact volume

2 ft³10% allowance

37 bags80 lb mix at 0.60 ft³

Without the allowance, the same slab requires 34 whole 80 lb bags. Always confirm product yield and project requirements before ordering.

Buying guidance

Check the order before checkout.

Confirm bag yield on the exact mix data sheet.
Ask the ready-mix supplier about delivery minimums and ordering increments.
Do not use this estimate to choose thickness, reinforcement, or mix strength.

Frequently asked questions

A second look at the estimate.

Why add a concrete allowance?

Uneven bases, form variation, spillage, and inaccessible remnants can increase the volume needed.

Does the tool design the slab?

No. It estimates material volume only; project design and structural requirements need appropriate professional guidance.

Can I compare bags and ready-mix?

Yes. The ticket shows cubic yards and metres alongside whole-bag estimates.

Sources and limitations

This calculator estimates material volume only. It does not determine slab thickness, reinforcement, mix strength, soil preparation, or structural suitability.

Last reviewed: July 16, 2026

Concrete Calculator