# Footing Concrete Calculator

Length, width and depth to yards and bags.

- Page: https://jianzhujisuan.com/en/footing-concrete
- Category: Concrete (https://jianzhujisuan.com/en/c/concrete)
- Chinese version: https://jianzhujisuan.com/zh/footing-concrete.md
- Data checked: 2026-10-25

## Quick result

With the default inputs (Length (total per run) 40 ft, Footing width 16 in, Footing depth 8 in, Number of runs 1 strips, Waste 10%): **Concrete required 1.45 yd³**

## Inputs

| Parameter | Type | Default | Unit | Note |
|---|---|---|---|---|
| Length (total per run) | number | 40 | ft |  |
| Footing width | number | 16 | in |  |
| Footing depth | number | 8 | in |  |
| Number of runs | number | 1 | strips |  |
| Waste | number | 10 | % |  |

## Formula

- **Volume = L × (W/12) × (D/12) × runs**: width and depth inches to feet
- **Cubic yards = volume ÷ 27**: 
- **Yards per ft = (W/12 × D/12) ÷ 27**: multiply by total length

## Worked example

One 40 ft run at 16 in wide and 8 in deep with 10% waste: 40 × 1.333 × 0.667 = 35.6 ft³, 39.1 ft³ with waste = 1.45 cubic yards, about 66 bags of 80 lb. That is 0.033 cubic yards per linear foot.

## Questions

### How wide and deep should the footing be?

A single-storey house strip footing commonly runs 16 in wide by 8 in deep with two #4 continuous bars; two storeys or heavier loads go to 20 in wide and 10-12 in deep. The actual size comes from the drawings and local code, and poor bearing soil needs more width or depth. The governing check is that the base area keeps soil pressure below bearing capacity - a stronger mix will not fix an undersized footing.

### Why is a gravel blinding layer needed?

The gravel layer spreads the load, gives a flat dry surface to work on, and breaks capillary rise. Pouring straight onto soil lets cement paste bleed into the ground, so the effective thickness drops and strength with it, and cover to the reinforcement cannot be controlled. Four to six inches is enough and it does not need heavy compaction.

### Do I need to correct for corner overlaps?

No. Adding the run lengths double counts the intersection, but the corner is the same concrete in practice, so that volume is not real. Overlap typically runs 3-8% of the total against a 10% waste allowance, so the two broadly cancel and the answer stands. On very short runs with many corners the overlap share rises - drop the waste to 5% in that case.

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