Concrete Footing Calculator
Your estimate
- Without waste
- 1.32 yd³35.6 ft³ · 1.01 m³
- Weight
- 5,202 lb2.6 tons · 2,359 kg
- Estimated cost
- $239
Strip footings for walls, pads for posts and round piers — with as many footings as you need.
Updated 2026-10-20 · Based on: bag yields printed by concrete-mix makers (0.30–0.60 ft³ per bag) and a 1.54 dry-volume factor.
How to use the Concrete Footing Calculator
- Pick strip, pad or round pier.
- Enter the length, width and depth of one footing (or diameter and depth for a pier) and how many there are.
- Add waste — 10–15 % for footings dug straight into soil.
- Read the cubic yards or bags.
Formula
Strip or pad = length × width × depth × count. Pier = π × (diameter ÷ 2)² × depth × count.
A typical strip footing 16 in wide and 8 in deep needs about 0.033 yd³ per foot of wall.
Worked example
With the values preset in the calculator above: (Strip footing)
- Length
- 40 ft
- Width
- 16 in
- Thickness
- 8 in
- Quantity
- 1
- Extra for waste
- 10 %
- Bag size
- 80 lb bags
- Concrete needed (with waste)
- 1.45 yd³ (39.1 ft³)
- Without waste
- 1.32 yd³ (35.6 ft³)
- Bags
- 66
- Weight
- 5,202 lb (2.6 tons)
- Estimated cost
- $239
Footing size rules of thumb
- Width: about twice the wall thickness (16 in for an 8 in wall).
- Depth: at least 6–8 in thick and below the frost line.
- Piers for decks: often 10–12 in diameter, 4 ft deep in cold climates.
- Always follow your local building code and soil conditions.
Frequently asked questions
How much concrete for a 40 ft footing?
A 40 ft strip footing 16 in wide and 8 in deep needs 1.32 yd³ (35.6 ft³) before waste.
How many bags for a deck footing?
A 12 in round pier 4 ft deep takes about 6 bags of 80 lb concrete with 10 % extra.
Do footings need rebar?
Most codes require two #4 bars in continuous footings. Pad and pier footings usually get rebar too — check your plans.
More calculators
Estimates only — check quantities with your supplier and local building code before you order.