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Concrete Footing Calculator

Size continuous strip footings and spread pad footings by length, width, and depth. Get yardage and bag counts with a waste factor that accounts for over-dug trenches.

Concrete Footing Calculator

The live calculator embeds here. Enter your dimensions to get cubic yards, bag counts, and cost in seconds.

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The basics

How the calculator works

  • 1

    Choose footing type

    Continuous (strip) footings run by linear foot; spread footings are individual pads. Pick the right one so the volume math fits.

  • 2

    Enter width and depth

    Standard residential footings are often 16–24 inches wide and 8–12 inches deep. Enter your print dimensions.

  • 3

    Enter total length or pad count

    For continuous footings, total the linear feet. For spread footings, enter the count and pad size.

  • 4

    Add extra waste for trenches

    Footings over-dig. Bump waste to 15% for hand-dug or backhoe trenches with bulging walls.

Show the math

The formula

Cubic Yards = (Width ft × Depth ft × Length ft) ÷ 27

A continuous footing is a long rectangular prism. Convert width and depth from inches to feet, multiply by total linear length, and divide by 27. Spread footings use length × width × depth per pad, multiplied by pad count.

Worked example

A continuous footing 20 inches wide, 10 inches deep, running 120 linear feet.

  1. 1.20 in = 1.667 ft wide, 10 in = 0.833 ft deep
  2. 2.1.667 × 0.833 × 120 = 166.6 cubic feet
  3. 3.166.6 ÷ 27 = 6.17 cubic yards
  4. 4.6.17 × 1.15 (15% trench waste) = 7.10 cubic yards

Order 7.25 cubic yards.

20+ years in the field

Real contractor tips

Footings always over-pour

Trench walls bulge and the bottom is never flat. A 10–15% waste factor on footings is not padding — it is realistic.

Mind the frost line

Footing depth is driven by local frost depth, not just load. Check your code minimum before you dig — a shallow footing fails inspection.

Keystep at grade changes

Stepped footings on a slope add volume at each step. Save each run as its own area so the total is right.

Pour footings and walls separately

Unless you are doing monolithic, footings and stem walls are separate pours. Keep them as separate areas in the job.

Avoid these

Common mistakes contractors make

  • Using too small a waste factor on over-dug trenches.
  • Forgetting the added volume at stepped footings.
  • Mixing spread and continuous footing math.
  • Ignoring local frost-depth requirements for footing depth.
  • Not counting pad footings under posts and columns.

Versus typical concrete calculators

  • Separate handling for continuous vs spread footings.
  • Higher default waste factor suited to trenches.
  • Save every footing run under one job.
  • Bag counts and yardage in one place.

Versus heavy takeoff software

  • No desktop install or license seat.
  • Works in the trench from your phone.
  • Free to start.
  • Concrete-focused, not a full estimating suite.

Frequently asked questions

Residential footings are commonly 16–24 inches wide, typically twice the wall thickness, sized to the soil bearing capacity and load. Always confirm against your engineered plans and local code.

Stop guessing yardage on the back of a napkin

Run your next pour through the calculator, save the job, and keep every area in one place. Free to start.

Open the App