Strip Footing Calculator — m to m³, bags, cost
How to use this calculator
Enter the footing run — a straight wall, L-shape (2 legs), U-shape (3 legs), or full perimeter rectangle — and pick the unit (m, cm or mm). Set the cross-section: width is usually twice the wall thickness (40 cm under a 20 cm block wall) and depth is the poured concrete itself, not the trench. The calc returns cubic meters or bag counts for the order, longitudinal rebar lengths with 40db laps, and a labor line so you have a takeoff before the dig. Tap any dimension on the diagram to jump to its input.
Cost — pick ready-mix delivery per m³, 50 kg bags, or 25 kg bags. Select your currency (EUR, PLN, CZK, SEK, etc.) in the settings below.
Reinforcement — longitudinal rebar Ø10–Ø16 (B500B) running lengthwise, plus optional stirrups/ties per EN 1992-1-1, with lap splices at 40db (§8.7).
Labor — rate per linear meter, per m³, or a flat price. Grand total sums all active sections.
Saved Calculations
| Time | Layout | Length | Vol m³ | Cost | Rebar | Rebar | Labor | Total |
|---|
How to Calculate Concrete for a Strip Footing (Metric)
A strip footing (continuous or wall footing) is the concrete band poured under a load-bearing wall to spread the wall load onto the soil. Volume is the cross-section (width × depth) carried along the full run, so a long, slender band absorbs ready-mix quickly — a 12 m × 0.40 m × 0.25 m footing is about 1.2 m³. Order ready-mix above roughly 1 m³; below that, bagged concrete usually wins on price and avoids a part-load surcharge. The 5–10% waste allowance covers over-cut trench faces and uneven blinding — raise it toward 15% for hand-dug trenches in soft ground. When sizing a foundation, work out the wall footing here, then add isolated column bases with the spread footing calculator and deep supports with the concrete pier calculator.
Formulas
Volume: V = total length × width × depth. For a closed rectangle the total length = 2 × (L + W); L and U layouts sum their straight legs. A 50-kg bag of dry concrete mix yields ≈ 0.024 m³ of placed concrete; a 25-kg bag ≈ 0.012 m³ — roughly 42 × 50-kg bags per cubic metre. Concrete weighs 2,400 kg/m³. For a standalone bag count use the concrete bag calculator.
Reinforcement per EN 1992-1-1 (Eurocode 2)
Strip footings carry longitudinal rebar (Ø10–Ø16 B500B) over the full length with lap splices at 40db per EN 1992-1-1 §8.7 — 480 mm for Ø12 bar. Standard 6 m bars set the splice count. Optional Ø6 stirrups at 150–300 mm tie the cage where the footing also works as a grade beam. Minimum cover is 40–75 mm by exposure class (EN 1992-1-1 §4.4.1); 75 mm applies for concrete cast directly against soil without blinding. A reinforced wall footing bridging weak spots is effectively a shallow grade beam; for pile-supported foundations size the cap with the pile cap calculator.
Ordering tips & jobsite notes
Across most of the EU in 2025, C25/30 ready-mix runs €110–160/m³ delivered, residential footing labor sits around €30–50 per linear metre, and B500B Ø12 rebar is €1.80–2.80/m at the merchant. The biggest takeoff mistake is forgetting the part-load surcharge — most batching plants add €60–120 for orders under ~3 m³, so a 12 m × 0.40 m × 0.25 m footing (≈ 1.2 m³) is often cheaper in 50 kg bags. Don't skip the keyway: a 100×40 mm chamfer pressed into the wet top gives the wall a positive shear key. Per EN 1992-1-1, cast against soil without blinding means 75 mm cover; with a 50 mm blinding layer drop to 50 mm. Trench bottoms must be on undisturbed soil below the local frost line.
FAQ
How wide should a strip footing be? Typically twice the wall width — a 0.40 m footing under a 0.20 m block wall. Light single-storey residential loads on firm soil can use 0.30 m.
How deep should a strip footing be? The poured thickness is 0.20 m minimum (0.25–0.30 m standard), but the underside must sit below the local frost line — 0.60–1.20 m in northern Europe. Footing depth here is the concrete thickness, not the trench depth.
Do I need rebar in a strip footing? Eurocode 2 requires minimum reinforcement where the footing is designed as reinforced concrete; two continuous Ø12 bars with Ø6 stirrups at 200 mm is the common residential configuration.
