Continuous Footing Concrete Volume — m³ + Cement Bags
A continuous footing (strip footing) is a shallow foundation that runs along the base of every load-bearing wall, spreading the structure's weight over a long, narrow band of soil. Before you pour or order concrete, you need to know the exact volume. The formula is simple: V (m³) = Length (m) × Width (m) × Depth (m) This calculator applies that formula instantly and also estimates cement bags. It is used by contractors, structural engineers, and self-builders for residential walls, retaining walls, and perimeter foundations — any time a continuous strip of reinforced or plain concrete must be poured at a consistent rectangular cross-section.
Continuous footing concrete volume: **V (m³) = Length × Width × Depth**. A 20 m footing at 0.40 m wide × 0.30 m deep needs **V = 20 × 0.40 × 0.30 = 2.40 m³**, which equals roughly 24 cement bags (50 kg each). Add 5–10% for waste before ordering.
When to use this calculator
- Estimating concrete volume and cement bags before purchasing materials for a house perimeter foundation
- Calculating how much ready-mix concrete to order for a retaining wall footing
- Verifying a contractor's material quote by independently computing the strip footing volume
- Planning a garage or workshop foundation to size the concrete truck delivery
Worked Example
- Length = 20 m, Width = 0.40 m, Depth = 0.30 m
- V = 20 × 0.40 × 0.30 = 2.40 m³
- Cement bags = 2.40 × 10 = 24 bags (50 kg each)
How it works
2 min readHow to Calculate Continuous Footing Concrete
A continuous (strip) footing is a rectangular prism. Its concrete volume is:
V = L × A × h
Where:
V = Volume of concrete (m³)
L = Total length of the footing (m)
A = Width of the footing cross-section (m)
h = Depth (height) of the footing cross-section (m)Example: A single-story house perimeter of 20 m, footing width 0.40 m, depth 0.30 m:V = 20 × 0.40 × 0.30 = 2.40 m³
Cement Bag Estimation
This calculator uses 10 bags (50 kg) per m³, a conservative estimate suited for structural 1:1.5:3 or 1:2:3 mixes standard in footings. For a lighter 1:2:4 mix, the figure drops to about 7–8 bags/m³.
Bags = V × 10 (1:1.5:3 structural mix — conservative)
Bags = V × 7 (1:2:4 lean mix — residential, low load)Always add 5–10% waste to both concrete volume and cement bag count before placing the order.
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Reference Table — Concrete Volume per Linear Meter
| Width (m) | Depth (m) | m³ per Linear Meter | Bags/m (1:1.5:3) | Bags/m (1:2:4) |
|---|---|---|---|---|
| 0.30 | 0.20 | 0.060 | 0.60 | 0.42 |
| 0.40 | 0.25 | 0.100 | 1.00 | 0.70 |
| 0.40 | 0.30 | 0.120 | 1.20 | 0.84 |
| 0.50 | 0.35 | 0.175 | 1.75 | 1.23 |
| 0.60 | 0.40 | 0.240 | 2.40 | 1.68 |
| 0.70 | 0.50 | 0.350 | 3.50 | 2.45 |
| 0.80 | 0.60 | 0.480 | 4.80 | 3.36 |
Multiply volume/meter × total length to get total m³. Add 5–10% for waste.
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Typical Cases
Case 1 — Single-story residential perimeter (small house)
V = 20 × 0.40 × 0.30 = TOK0 Case 2 — Garden retaining wall footing
V = 8 × 0.50 × 0.35 = TOK0 Case 3 — Two-story house, heavier load
V = 48 × 0.60 × 0.45 = TOK0 ---
Common Errors to Avoid
1. Double-counting corners — Measure each wall's footing length using the centerline, or subtract one footing width per corner. For a simple 4-corner rectangle: corrected length = external perimeter − 4 × footing width.
2. Forgetting the waste factor — Never order exactly the calculated volume. Add 5–10% for spillage, form irregularities, and residual concrete in the truck drum.
3. Confusing footing width with wall width — A 0.20 m thick wall may sit on a 0.40 m wide footing. Use the footing's own cross-section dimensions.
4. Wrong mix for load — A 1:2:4 mix reaches roughly 15–20 MPa, adequate for lightly loaded one-story walls. Two-story or poor-soil conditions call for 1:1.5:3 (≈ 25–30 MPa).
5. Unit confusion — This calculator uses meters. Enter 0.40 m, not 40 cm.
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Related Calculators
Frequently asked questions
What is the formula for continuous footing concrete volume?
V (m³) = Length × Width × Depth. For example, a 20 m long footing at 0.40 m wide and 0.30 m deep gives V = 20 × 0.40 × 0.30 = 2.40 m³. This rectangular-prism formula applies regardless of reinforcement.
How many cement bags do I need per cubic meter of concrete?
For a structural 1:1.5:3 mix (cement:sand:gravel by volume), approximately 9–10 bags (50 kg each) per finished m³. For a lighter 1:2:4 residential mix, about 7–8 bags/m³. This calculator uses 10 bags/m³ as a conservative structural estimate. Always add 5–10% for waste.
How do I measure the total footing length correctly?
Measure using the centerline of each footing segment, not the outer wall face. At corners, two footings overlap — the standard correction is to subtract one footing width per inside corner. For a simple rectangular house with 4 corners: corrected length = external perimeter − 4 × footing width.
How deep should a continuous footing be to avoid frost heave?
The footing bottom must sit below the local frost depth. NOAA and IRC frost maps show depths ranging from near 0 in southern Florida to over 60 inches (1.52 m) in Minnesota. Chicago's requirement is about 42 inches (1.07 m). Check your local building department for the frost depth in your specific area.
What is a typical footing width for a one-story house?
IRC Section R403.1 requires a minimum of 12 inches (≈ 0.30 m) wide and 6 inches (≈ 0.15 m) thick for a one-story structure on adequate soil. For two-story buildings, minimums rise to 15 inches (≈ 0.38 m) wide and 7 inches (≈ 0.18 m) thick. Poor soil bearing capacity may require wider footings regardless of story count.
Can I use this calculator for ready-mix concrete ordering?
Yes. Add 5–10% to the calculated volume before ordering. To convert m³ to cubic yards (common in the U.S.), multiply by 1.308: e.g., 2.40 m³ × 1.308 = 3.14 yd³. Most ready-mix suppliers charge a short-load fee for orders under about 3 m³, so it can be more economical to order slightly more.
What concrete strength should I specify for strip footings?
The IRC (R402.2) requires a minimum of 2,500 psi (≈ 17 MPa) for footings in most climates, and 3,000 psi (≈ 21 MPa) in areas subject to freeze-thaw cycles. For structural loads, specify the f'c designation to your ready-mix supplier rather than relying on field-mixed ratios.
Does this calculator apply to reinforced concrete footings?
Yes. Rebar displaces less than 1–2% of the total concrete volume, so no adjustment is needed for material estimation. Order concrete by the V = L × A × h formula and buy rebar separately, per the structural engineer's rebar schedule.
How much extra concrete should I order as waste?
The industry standard is 5–10% overage. For volumes under 2 m³ (hand mixing), add 10%. For ready-mix truck deliveries, add 5–8%. Example: a calculated 2.40 m³ becomes a 2.65 m³ order at 10% waste.