Concrete Footing Volume: Strip, Pad and Steps

A footing takeoff starts with the approved concrete dimensions. List each strip, pad, and level change as a defined section, calculate its volume, then check whether any sections cover the same corner or intersection.

Keep the measured concrete volume separate from over-excavation, a planning allowance, package yield, supplier rounding, and commercial minimums. Each stage answers a different quantity question.

How do you calculate concrete footing volume?

Convert length, width, and concrete depth to one unit, multiply them for each rectangular footing section, and add the non-overlapping section volumes. Multiply by the count when several pads have identical approved dimensions.

Rectangular section volume = quantity × length × width × depth

Measured footing volume = sum of section volumes − duplicated intersection volumes

Use cubic metres when the dimensions are in metres. Use cubic feet when the dimensions are in feet, then divide by 27 for cubic yards. NIST Handbook 133 lists 1 yd³ as 27 ft³ and 1 m³ as 1.307951 yd³.

Which footing measurements belong in the takeoff?

Record the dimensions that bound the concrete itself. A wall thickness, reinforcement cage, excavation width, or outside face of formwork may describe a different boundary.

Separate footing concrete from blinding, a mud slab, keyways, pedestals, grade beams, walls, piers, slab thickenings, and backfill. Add one of those items only when its specified geometry belongs to the same order record.

Worked example: a strip footing with 4 pads

An approved imperial schedule has a 36 ft strip footing that is 18 in wide and 10 in deep. It also has 4 pads, each 3 ft × 3 ft × 12 in.

1. Convert strip width: 18 ÷ 12 = 1.5 ft.
2. Convert strip depth: 10 ÷ 12 = 0.833333 ft.
3. Strip volume: 36 × 1.5 × 0.833333 = 45 ft³.
4. Pad volume: 4 × 3 × 3 × 1 = 36 ft³.
5. Total measured volume: 45 + 36 = 81 ft³.
6. Convert to cubic yards: 81 ÷ 27 = 3.00 yd³.

The 3.00 yd³ result is measured geometry. It contains no allowance, supplier increment, bag yield, short-load minimum, or truck-capacity assumption.

How do you calculate a stepped strip footing?

Break the footing into non-overlapping rectangular sections at every change in width or concrete depth. Calculate each section with its own dimensions and add the results.

An approved metric schedule contains these 3 sections:

The NIST conversion gives 2.1325 × 1.307951 = 2.7892 yd³, rounded here to 4 decimal places. Keep 2.1325 m³ in the source schedule so later allowance and supplier calculations use the unrounded measured result.

Can you use average depth for stepped footings?

Use separate sections for discrete steps. One average depth can lose the length assigned to each depth, and the error grows when width also changes.

An average endpoint depth describes a truly linear depth transition only when the width stays constant and the approved shape is a prism with a linearly changing depth. A constructed step has distinct solids. Record the step lengths and dimensions shown by the approved detail.

How should footing corners and intersections be counted?

State the length convention first. Subtract an intersection once when 2 scheduled strip lengths both include the same concrete solid.

Example: 2 perpendicular strips are each 0.50 m wide and 0.25 m deep. Their lengths, measured to the outside ends, are 10 m and 8 m.

1. First strip: 10 × 0.50 × 0.25 = 1.2500 m³.
2. Second strip: 8 × 0.50 × 0.25 = 1.0000 m³.
3. Shared corner: 0.50 × 0.50 × 0.25 = 0.0625 m³.
4. Net volume: 1.2500 + 1.0000 − 0.0625 = 2.1875 m³.

The deduction belongs to this outside-length convention. Centreline lengths, clear non-overlapping segments, and takeoff software can treat intersections differently. Check the model or schedule before changing the total.

Should you use drawing dimensions or field dimensions?

Keep the approved takeoff and the accepted field revision as dated records. Use the revised field geometry for ordering only after the responsible project process confirms that the changed space will receive concrete.

Excavation volume and concrete volume can differ. Side clearance for forms, sloping, benching, working space, drainage, or a protective system may increase excavation without increasing footing concrete.

How do you record a field quantity change?

Preserve the original measured total and add a dated change line. Record the location, old dimensions, revised dimensions, volume difference, reason, approval, and whether the change affects allowance or supplier rounding.

Suppose the 2.1325 m³ stepped-footing fixture receives an approved 0.0800 m³ field addition. The revised measured volume is 2.2125 m³. If the project then approves a 3% planning allowance and the supplier confirms a 0.25 m³ selling increment:

1. Revised measured volume: 2.1325 + 0.0800 = 2.2125 m³.
2. Planning volume: 2.2125 × 1.03 = 2.278875 m³.
3. Supplier order: ceiling(2.278875 ÷ 0.25) × 0.25 = 2.50 m³.

The 3% allowance and 0.25 m³ increment are hypothetical fixture inputs. Obtain the project allowance and current supplier terms for the real order.

How do you convert footing volume to bags or ready mix?

Choose the supply route after the measured volume is checked. Package planning needs the selected product's current mixed yield and whole-package rounding. Ready-mix planning needs the supplier's current selling increment, mixture requirements, delivery details, site access, and placement plan.

• Enter the measured footing volume in the Concrete Bags Calculator when a named packaged product and its current mixed yield control the purchase.
• Use the Ready-Mix Concrete Calculator when a producer will supply the concrete and the project has the required order information.
• Check the Concrete Bag Yield Chart before entering product yield.
• Use the Ready-Mix Cubic-Yard Ordering guide to keep measured volume, allowance, selling increment, and invoice minimum separate.

ACI's ordering checklist includes quantity, delivery location, date and time, delivery rate, and required mixture properties. The project and producer supply those values. A footing-volume formula does not select them.

Common footing-volume mistakes

• Using wall thickness as footing width.
• Multiplying feet by inches without converting units.
• Using one average depth across discrete steps.
• Counting the same corner or crossing volume twice.
• Deducting a corner when the scheduled lengths are already net.
• Multiplying one pad by the wrong repeated quantity.
• Combining blinding, pedestal, wall, pier, grade beam, or slab thickening with the footing line.
• Treating excavation side clearance as footing concrete.
• Subtracting reinforcing-steel volume without an approved estimating method.
• Adding a default waste percentage before recording a field change.
• Rounding every section before the total is calculated.
• Converting to bags or truckloads with an unverified yield or capacity.

Return to the Concrete Planning hub for the related calculators and ordering guides.

Safety and scope limits

Footing work can include excavation collapse, underground utilities, water, loose material, mobile equipment, suspended loads, access, adjacent structures, formwork, reinforcement, and fresh-concrete hazards. OSHA 29 CFR 1926.651 requires expected underground installations to be located before excavation work under its U.S. scope and sets controls for access, water, adjacent structures, loose material, and inspections.

OSHA 29 CFR 1926.652 addresses cave-in protection and protective systems under its stated conditions. Applicable local law, site safety plans, competent-person inspections, project documents, equipment instructions, and qualified supervision control the work.

This quantity guide does not design the footing, excavation, forms, reinforcement, concrete mixture, access, protective system, placement, joints, testing, or curing. Stop the quantity handoff when the dimensions, site boundary, approval, or safety condition is unresolved.