Concrete Footing Calculator

Estimate concrete for strip footings, wall footings and post footings from length, width and depth, with cubic yards, cubic metres, bag checks, waste allowance and a printable footing pour note.

Concrete for footingsConcrete Footing Calculator uses the declared inputs to produce a transparent default result. Footing length: 40 ft; Footing width: 16 in; Footing depth: 12 in; Number of matching footings: 1; primary comparison: 40 and 16.

Footing lengthftFooting widthinFooting depthinNumber of matching footingsWaste / overdig allowance%Bag yieldft³/bag

Live math canvas

Your numbers, formula and explanation together

Concrete Footing Calculator: 79.6 cubic yards with cubic-metre, cubic-foot and bag-count checks. Concrete Footing Calculator uses the declared inputs to produce a transparent default result. Footing length: 40 ft; Footing width: 16 in; Footing depth: 12 in; Number of matching footings: 1; primary comparison: 40 and 16.

Formula applied

The exact method behind this answer

CalculationTime keeps the method visible so the number can be checked instead of blindly trusted.

Width feet = footing width inches ÷ 12. Depth feet = footing depth inches ÷ 12. Base cubic feet = length feet × width feet × depth feet × number of footings. Cubic yards = cubic feet ÷ 27. Order volume = base volume × (1 + waste percent ÷ 100). Cubic metres = cubic yards × 0.764554857984. Bags = ceiling(order cubic feet ÷ bag yield cubic feet).

Apply the formulaWidth feet = footing width inches ÷ 12. Depth feet = footing depth inches ÷ 12. Base cubic feet = length feet × width feet × depth feet × number of footings. Cubic yards = cubic feet ÷ 27. Order volume = base volume × (1 + waste percent ÷ 100). Cubic metres = cubic yards × 0.764554857984. Bags = ceiling(order cubic feet ÷ bag yield cubic feet).79.6 cubic yards with cubic-metre, cubic-foot and bag-count checksConcrete Footing Calculator uses the declared inputs to produce a transparent default result. Footing length: 40 ft; Footing width: 16 in; Footing depth: 12 in; Number of matching footings: 1; primary comparison: 40 and 16.

Your live breakdown

Current inputs in the calculation

These values come from the controls above and update when the calculator changes.

Footing length: 40 ft
Footing width: 16 in
Footing depth: 12 in
Number of matching footings: 1
Waste / overdig allowance: 10 %
Bag yield: 0.6 ft³/bag

Resulting answer

79.6 cubic yards with cubic-metre, cubic-foot and bag-count checks

Concrete Footing Calculator uses the declared inputs to produce a transparent default result. Footing length: 40 ft; Footing width: 16 in; Footing depth: 12 in; Number of matching footings: 1; primary comparison: 40 and 16.

Answer: 79.6 cubic yards with cubic-metre, cubic-foot and bag-count checks
Live support: Concrete Footing Calculator uses the declared inputs to produce a transparent default result. Footing length: 40 ft; Footing width: 16 in; Footing depth: 12 in; Number of matching footings: 1; primary comparison: 40 and 16.

Assumptions used

What this answer assumes

Best for strip footings, garden wall footings, shed footings, small foundation estimates, quote notes and construction math worksheets where the size and waste allowance need to stay auditable.

The calculator treats each footing as a straight rectangular prism; stepped, haunched, belled or irregular excavations need separate checks.
Width and depth are entered in inches and converted to feet before volume is calculated.
The allowance is shown separately so overdig, spillage and ordering margin do not hide the measured concrete requirement.
Bag count is rounded up to whole bags using the entered bag yield; actual bag yield depends on product, water addition and site practice.
This calculator is for quantity estimating only. Footing size, reinforcement, soil capacity, frost depth, inspection and code compliance must be confirmed by qualified local authority or professionals.

Master’s Tip

How to use the result well

Master’s Tip: print the footing dimensions before ordering concrete and keep structural design separate from quantity takeoff. A trench that is only two inches wider than planned can materially change the order on a long run.

Printable record

What belongs in the saved calculation

Save the inputs, result, formula, assumptions, page URL and date together so the calculation can be reviewed later.

Footing length: 40 ft
Footing width: 16 in
Footing depth: 12 in
Number of matching footings: 1

Embeddable calculator

Embed this calculator

Copy a clean iframe version with the required CalculationTime attribution link built in.

Formula

Width feet = footing width inches ÷ 12. Depth feet = footing depth inches ÷ 12. Base cubic feet = length feet × width feet × depth feet × number of footings. Cubic yards = cubic feet ÷ 27. Order volume = base volume × (1 + waste percent ÷ 100). Cubic metres = cubic yards × 0.764554857984. Bags = ceiling(order cubic feet ÷ bag yield cubic feet).

Worked example

For one 40 ft footing that is 16 in wide and 12 in deep, width = 16 ÷ 12 = 1.333 ft and depth = 1 ft. Base volume = 40 × 1.333 × 1 × 1 = 53.33 ft³, or 1.98 yd³. With a 10% allowance, order about 2.17 yd³.

Professional note

Regional and unit assumptions

Standard or basis: rectangular volume arithmetic with 27 cubic feet per cubic yard and 1 cubic yard ≈ 0.764554857984 cubic metres. Use local building codes, permit drawings, engineer details and ready-mix supplier requirements as the authority for structural footing work.

Assumptions and limitations

The calculator treats each footing as a straight rectangular prism; stepped, haunched, belled or irregular excavations need separate checks.
Width and depth are entered in inches and converted to feet before volume is calculated.
The allowance is shown separately so overdig, spillage and ordering margin do not hide the measured concrete requirement.
Bag count is rounded up to whole bags using the entered bag yield; actual bag yield depends on product, water addition and site practice.
This calculator is for quantity estimating only. Footing size, reinforcement, soil capacity, frost depth, inspection and code compliance must be confirmed by qualified local authority or professionals.

Methodology & Accuracy

How this calculator is checked

CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.

Formula used

Standard or basis

Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.

Master's Tip

Questions

How do I calculate concrete for a footing?

Convert footing width and depth from inches to feet, then multiply length × width × depth × number of footings. Divide cubic feet by 27 for cubic yards and add a separate waste allowance.

Should I add waste when ordering footing concrete?

Usually yes. A visible allowance helps cover over-excavation, uneven trench bottoms, spillage and supplier rounding. The right margin depends on site conditions and supplier minimums.

Can this calculator design my footing size?

No. It estimates concrete quantity only. Footing dimensions, reinforcement, soil capacity, frost depth and code compliance need local drawings, inspection or professional advice.

How many bags of concrete do I need for footings?

The page divides the order cubic feet by the bag yield you enter, then rounds up to whole bags. Check the yield printed on the exact bag product.

What should I print for a footing pour record?

Print the length, width, depth, number of footings, base cubic feet, cubic yards or cubic metres, allowance, bag yield, formula, assumptions, page URL, date and site notes.

Calculation note

Footing estimates are simple volume calculations, but the consequences of confusing design and quantity are serious. A useful calculator keeps the concrete takeoff visible while warning that structural adequacy belongs to local code, drawings and professional judgement.

Quantity takeoff is not structural design

Length, width and depth can estimate concrete volume, but they do not prove that a footing is suitable for the load, soil, frost conditions or inspection rules.

The trench controls the pour

Footing concrete is often poured into an excavated trench or form. Real trenches can be wider, deeper or rougher than the drawing, which is why the allowance should remain visible.

A printable pour note protects the order

A one-page record with dimensions, allowance, supplier unit and notes helps compare the measured takeoff with the concrete ordered, delivered and poured.

Sources and further readingNIST Handbook 44 Appendix C — General Tables of Units of Measurement BIPM — The International System of Units International Code Council — International Residential Code information