Concrete Footing Calculator

Last updated: June 2026

Footing length

Footing width

Footing depth

Waste

Concrete volume

1.485 m3

25kg bags

124 bags

40kg bags

79 bags

Formula

footing concrete = length x width x depth x waste allowance.

About this calculator

The Concrete Footing Calculator estimates concrete volume for strip footings, trench fill, garden walls, outbuildings, and simple foundation runs using length, width, depth, and waste allowance.

Concrete Footing Calculator method

The calculator uses metric project dimensions, applies the material formula shown below, and then adds any waste or allowance entered. Quantities are rounded up where materials are normally purchased as whole boards, sheets, blocks, rolls, bags, or packs.

footing volume = length x width x depth
total volume = footing volume x number of runs
order volume = total volume x (1 + waste percentage)

How to use the Concrete Footing Calculator

Measure the footing length, width, and depth in metres.
Enter the number of identical footing runs if applicable.
Add waste for uneven trench sides, spillage, and level variation.
Review cubic metres and bag or delivery estimates if shown.
Check whether the project needs building regulations, structural advice, or inspection.

Worked examples

Garden wall footing

Input: 8m long, 0.45m wide, 0.3m deep, 10% waste

Calculation: 8 x 0.45 x 0.3 x 1.10

Result: About 1.19m3 of concrete.

Two footing runs

Input: Two runs, each 5m x 0.4m x 0.25m

Calculation: 5 x 0.4 x 0.25 x 2

Result: About 1.00m3 before waste allowance.

When this calculator is useful

The Concrete Footing Calculator estimates concrete volume for strip footings, trench fill, garden walls, outbuildings, and simple foundation runs using length, width, depth, and waste allowance.

Use it before ordering materials, comparing supplier pack sizes, or checking whether a first estimate is realistic. Keep the result with your measured dimensions so you can update the calculation if the project size changes.

Inputs that affect the result

Ground conditions: Soil type, frost depth, load, trees, and drainage can change footing requirements.
Trench shape: Uneven sides and soft spots often increase actual concrete used.
Delivery size: Ready-mix minimum loads and bag yields can affect buying decisions.

Common mistakes to avoid

Check 1: Structural foundations should not be sized only from a material calculator.
Check 2: Water in the trench can affect concrete quality and volume.
Check 3: Local building control or engineer input may be needed for load-bearing work.

Material planning notes

Planning point	Why it matters
Measure finished area	Use the actual finished dimensions after allowing for openings, edges, posts, slopes, or returns.
Allow for waste	Cuts, breakages, joins, pattern matching, awkward shapes, and site handling usually mean ordering more than the exact calculated amount.
Round purchase quantities up	Most materials are bought as full boards, sheets, bags, blocks, rolls, packs, or bulk deliveries.
Check supplier specifications	Coverage, density, sheet size, block size, and pack size vary by product and supplier.

Limitations and safety

This calculator is for general project planning only. It does not replace a structural design, building regulations advice, manufacturer instructions, supplier specifications, or a competent tradesperson. Projects involving structure, roofs, retaining walls, foundations, drainage, electrics, gas, or safety-critical work should be checked properly before buying materials or starting work.

Frequently asked questions

Should I order exactly the calculated quantity?

Usually no. Order in the nearest practical pack, board, sheet, bag, roll, or delivery quantity, and keep a sensible waste allowance for cuts and mistakes.

What waste allowance should I use?

Simple rectangular jobs may only need 5-10%. Patterned, angled, fragile, or irregular projects may need more. The right allowance depends on the material and layout.

Why might my supplier quantity differ?

Suppliers use specific product sizes, densities, coverage rates, and pack quantities. Use the calculator as a planning estimate, then compare it with the product label or datasheet.

Can I use this for professional building work?

It can help with a rough take-off, but professional work should be checked against drawings, specifications, site conditions, and relevant UK rules or standards.

What measurements should I double-check?

Check length, width, depth, height, spacing, openings, pitch, and units. A small unit mistake can change a material order by a large amount.

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What does this mean?

This calculator is designed to help you understand the likely number before you make a decision or start an application.

Your result should be checked against official UK guidance, especially if your circumstances include dependants, exemptions, prior leave, or a complex immigration history.

Treat the figure as a planning tool rather than legal advice. Where the answer affects an application deadline or major payment, speak to an authorised adviser.