Strip Footing Calculator
Concrete, blinding, formwork and base area for strip footings.
Quick answer
With the default inputs: Total length 60 m · Section shape Rectangular · Top width 0.37 m etc.Footing concrete 11.02 m³
Edit the inputs below to recalculate.Inputs
Result
Footing concrete
11.02m³
| Concrete per metre | 0.1836m³/m |
| Section area | 0.1800m² |
| Net concrete | 10.80m³ |
| Blinding volume | 4.80m³ |
| Blinding width | 0.80m |
| Footing side formwork | 36.0m² |
| Blinding side formwork | 12.0m² |
| Base area | 36.0m² |
| Base area per metre | 0.60m²/m |
Strip footing quantities are measured by the designed volume without deducting reinforcement, cast-in items or holes under 0.3 m². Blinding is measured by volume and typically projects 100 mm each side. Formwork is the contact area, and for trapezoidal sections it follows the sloping face rather than vertical height — an easily missed point worth 10-20% extra. Reinforcement is not covered: footing rebar needs a bending design against the imposed load and soil reaction.
Formula
| Section (rectangular) | A = bottom width × height |
| Section (trapezoidal) | A = (top + bottom) ÷ 2 × height |
| Concrete volume | V = A × total length × (1 + waste) |
| Blinding | V = (bottom + 2 × projection) × thickness × length |
| Side formwork | S = 2 × side length × total length |
| Sloping length | L = √(height² + ((bottom − top) ÷ 2)²) |
60 m of 0.6 m by 0.3 m footing with 100 mm blinding projecting 100 mm: 11.02 m³ of concrete (10.80 net), 4.80 m³ of blinding, 36.0 m² of side formwork, 12.0 m² of blinding formwork and 36 m² of base area.
FAQ
Why not multiply height by length for a trapezoidal footing?
Because the sides are battered and the formwork lies on the slope, whose length is √(h² + ((bottom − top)/2)²) — longer than the vertical height. For 370 top, 600 bottom and 300 high the sloping length is 321 mm, 7.1% more. Small on one section, but 60 m of wall adds 2.55 m², and flatter slopes differ far more. Missing this overruns the formwork budget.
Does blinding need formwork?
Depends on method. Blinding cast directly against undisturbed soil (earth mould) needs no formwork — only concrete is measured. Cast on fill or against brick templates, it needs side formwork. Most footing blinding uses the earth mould, so budgets usually omit it, though a site instruction can claim it if formwork was actually erected. It is listed separately here so you can take it or leave it.
How is the stepped brick footing calculated?
The stepped courses are measured by volume, usually by the equivalent-height method: the step volume is converted to an equivalent height of the same wall width and added from a table. Equal courses (quarter-brick offset every two courses) and alternate courses differ. Brick footing volume = wall width × (design height + equivalent height) × length, less ring beams, tie columns and ground beams.
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.