Footing Size Calculator Guide - Width, Depth, Concrete
Use a footing size calculator guide to plan width, depth, length, cubic yards, rebar, excavation, soil, frost, and contractor quote checks.
A footing size calculator can estimate concrete volume from width, depth, and length, but it cannot decide the correct footing size by itself. Soil, load, frost depth, wall type, pier spacing, reinforcement, and code requirements matter before a footing is poured.
Use the Concrete Footing Calculator for volume and the Concrete Footing Calculator Guide for examples. Compare contractor bids in the Concrete Quote Reviewer.
Competitor pages such as ConcreteCalculator.pro's footing calculator and ConcreteCalculatorMax's footing calculator target volume. This page adds the size and quote questions.
Quick answer
For footing volume:
cubic yards = length ft x width ft x depth ft / 27
Example: a 40 ft continuous footing that is 16 in wide and 8 in deep needs about 1.32 yd3 before waste, or about 1.45 yd3 with 10% waste.
Footing width, depth, bearing, frost, reinforcement, and inspection requirements should be confirmed with a qualified local professional.
Footing size inputs
| Input | Why it matters |
|---|---|
| Total run length | Sets the length of the footing. |
| Width | Affects bearing area and concrete volume. |
| Depth | Affects volume and frost or design requirements. |
| Soil condition | Poor soil may require a different design. |
| Load | Walls, decks, posts, and additions differ. |
| Reinforcement | Rebar size and placement should be written. |
| Excavation | Trench depth and access can drive labor. |
For cost, see Concrete Footing Cost per Linear Foot and Footing Cost Calculator Guide.
Common footing volume examples
| Footing run | Width x depth | Concrete before waste | With 10% waste |
|---|---|---|---|
| 20 ft | 12 in x 8 in | 0.49 yd3 | 0.54 yd3 |
| 40 ft | 16 in x 8 in | 1.32 yd3 | 1.45 yd3 |
| 60 ft | 18 in x 10 in | 2.78 yd3 | 3.06 yd3 |
| 80 ft | 24 in x 12 in | 5.93 yd3 | 6.52 yd3 |
Use these as volume checks only. They are not footing design recommendations.
Quote checklist
| Quote line | Confirm |
|---|---|
| Footing dimensions | Width, depth, total run, and sections. |
| Excavation | Spoils, trench depth, access, and cleanup. |
| Rebar | Size, quantity, laps, chairs, and dowels. |
| Inspection | Who schedules and who pays. |
| Concrete order | Yards, delivery, pump, buggy, or wheelbarrow. |
| Exclusions | Rock, water, unsuitable soil, engineering, permits. |
Size vs estimate risk
A footing size calculator is useful after the planned dimensions are known. It is not the tool that should choose dimensions for a structural footing. Treat searches such as "footing size calculator" as two separate jobs: first confirm the required width, depth, frost, soil, load, and reinforcement path; then use the calculator to estimate concrete, delivery, rebar, excavation, inspection, and quote scope.
FAQ
How do I calculate footing concrete?
Multiply footing length by width by depth, keep all dimensions in feet, divide by 27 for cubic yards, then add waste.
Can a calculator choose footing width?
No. A calculator can estimate volume, but footing size depends on loads, soil, frost, code, and structural requirements.
What is the difference between footing size and footing volume?
Footing size is the design dimension. Footing volume is the concrete quantity created by those dimensions.
Should rebar be included in a footing quote?
If reinforcement is required, the quote should state bar size, spacing, laps, dowels, chairs, and inspection responsibility.
When should I get professional help?
Use a qualified local professional for structural loads, retaining walls, additions, poor soils, frost depth, permits, or inspections.
Next step
Calculate volume in the Concrete Footing Calculator, then compare scope in the Concrete Quote Reviewer. Contractors can prepare line items in the Concrete Proposal Kit.
Quote planning next step
Turn this guide into a concrete buying check
Run the matching calculator, then compare ready-mix, bagged concrete, delivery fees, access needs, and quote gaps before you buy materials or approve a contractor number.