Footing Calculator
Take off a footing pour: continuous (strip) footings from width, depth, and length, or pad footings by size and count — concrete in cubic feet and cubic yards with a waste allowance, plus rebar length and weight for the continuous runs or the bars-each-way mats, at ASTM A615 nominal weights. Then print it as a material order sheet. It quantifies the footing on your drawings; it does not size one. Free, no login.
Footing
Concrete & Rebar
Continuous strip. Includes concrete waste; rebar excludes laps, hooks, cover & dowels. Planning figures — confirm against the structural drawings.
Footing Calculator — Material Order Sheet
Prepared with NORDIX — nordixhq.com/tools/footing-calculator
| Type: Continuous strip | Section: 16" × 8" | Length: 100 ft | Rebar: 2 × #4 | Waste: 10% |
| Material | Qty | Unit | Notes |
|---|---|---|---|
| Ready-mix concrete | 3.62 | yd³ | 97.78 ft³, waste included |
| #4 rebar | 200 | ft | 133.6 lb, before laps |
Method: footing volume including the waste allowance; rebar as continuous runs (strip) or a bars-each-way mat per pad, ASTM A615 nominal weights, excluding laps, hooks, cover, and dowels. Empirical planning figures — confirm against the structural drawings before ordering.
How this calculator works
A footing is a box, so the volume is straight geometry with your waste factor on top — width and depth in inches, length in feet:
ft³ = (W÷12) × (D÷12) × L × (1 + waste%) · yd³ = ft³ ÷ 27
Pad mode figures the same volume per pad and multiplies by the count. The 10% default waste is a planning allowance sized for trench-formed footings, where overdig and rough trench walls soak up concrete — clean formed footings may need only 5%. Rebar is counted as continuous runs × length (strip) or a bars-each-way mat per pad, converted to weight with the ASTM A615 nominal bar weights (#4 = 0.668 lb/ft, #5 = 1.043 lb/ft) — deliberately excluding laps, corner bars, hooks, and dowels, which come off the drawing details. Depth means the concrete thickness, not depth below grade: frost depth affects excavation and wall height, not the footing’s own volume.
Worked example
A 16" wide × 8" deep continuous footing, 100 ft long, two #4 continuous bars, 10% waste:
- Concrete: (16÷12) × (8÷12) × 100 × 1.10 = 97.78 ft³.
- Yards: 97.78 ÷ 27 = 3.62 yd³ — order 4 yards.
- Rebar: 2 runs × 100 ft = 200 ft, at 0.668 lb/ft = 133.6 lb — before laps: 100-ft runs from 20-ft sticks need four lap splices per run, added per the drawings.
Enter the same footing above (the calculator’s defaults) to reproduce it, then print the order sheet.
Reference: concrete per foot for common footing sections
Pure geometry, before waste. Footing dimensions themselves come from the drawings, a prescriptive code table, or the engineer — not from this list.
| Section (W × D) | ft³ per ft | yd³ per 100 ft |
|---|---|---|
| 12" × 6" | 0.5 | 1.85 |
| 16" × 8" | 0.889 | 3.29 |
| 18" × 10" | 1.25 | 4.63 |
| 20" × 10" | 1.389 | 5.14 |
| 24" × 12" | 2 | 7.41 |
Frequently asked questions
How do I calculate cubic yards of concrete for a footing?
Width times depth times length, divided by 27 to go from cubic feet to cubic yards. This calculator takes width and depth in inches and length in feet, so a 16 x 8 in. footing 100 ft long is (16/12) x (8/12) x 100 = 88.9 cubic feet, or about 3.3 yards before waste. Pad mode figures the same volume per pad and multiplies by the pad count.
How much extra concrete should I order for footings?
The calculator defaults to 10% waste, which is reasonable for trench-formed footings — trench walls are never as neat as formwork, and overdig soaks up concrete fast. For clean, formed footings 5% may be enough; for rough or sloughing ground go higher. It is an estimate, and coming up a half-yard short with a truck on site costs more than the cushion.
How much rebar is in a continuous footing?
The calculator multiplies the number of continuous bars by the footing length, then converts to weight using standard nominal bar weights — #4 = 0.668 lb/ft, #5 = 1.043 lb/ft. It deliberately excludes laps, corner bars, hooks, and dowels: bars come in stock lengths, every splice adds lap length per your drawings, and corners and intersections take extra bars. Add those from the plan details before ordering.
What size footing do I need?
That is an engineering and code question — footing width, thickness, and reinforcing come from the soil bearing capacity, the loads, and frost depth, set by the drawings, a prescriptive code table, or an engineer. This calculator does not size footings; it takes the dimensions you already have and turns them into concrete yardage and rebar quantities for the estimate.
Does depth mean footing thickness or depth below grade?
Thickness. The depth input is the vertical dimension of concrete — enter 8 and you get 8 in. of concrete in the volume, no matter how far below grade the footing sits. Frost depth affects excavation and wall height, not the footing's own concrete volume.
How does pad footing mode work?
Enter the pad's width, length, and depth in inches, the number of identical pads, and the bars each way in the mat. The calculator figures volume per pad times the count (plus waste), and the mat steel as that many bars spanning each direction per pad — again excluding laps, hooks, standees, and dowels into piers or columns.
Method: box volume (W × D × L, pad volume × count) plus the entered waste allowance — the waste percentage is a planning figure, not a standard; rebar as continuous runs or bars-each-way mats at ASTM A615 nominal weights, excluding laps, hooks, corner bars, standees, cover adjustments, and dowels into walls or columns. Footing size, depth below grade, and reinforcing are engineering and code questions (soil bearing, loads, frost depth) settled by the drawings or the engineer of record — this tool only prices what they specify.
Pair with the Construction Calculator for slabs and columns on the same pour, the Rebar Calculator for mat steel by spacing, or the Block / CMU Calculator for the foundation wall above.