算BuildCalc

Strip Footing Calculator

Concrete, blinding, formwork and base area for strip footings.

Quick answer

With the default inputs: Total length 60 · Section shape Rectangular · Top width 0.37 etc.Footing concrete 11.02 m³

Edit the inputs below to recalculate.
Top width mBottom width mFooting height mBlinding thickness m
Top width is the wall or column width and bottom width sets the bearing pressure. Blinding projects 100 mm past the base each side, typically 100 mm thick.

Inputs

Sum of all strip lengths
For rectangular sections the bottom width is used and top width ignored
Set 0 for no blinding
Usually 100 mm each side
%

Result

Footing concrete
11.02m³
Concrete per metre0.1836m³/m
Section area0.1800m²
Net concrete10.80m³
Blinding volume4.80m³
Blinding width0.80m
Footing side formwork36.0m²
Blinding side formwork12.0m²
Base area36.0m²
Base area per metre0.60m²/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 volumeV = A × total length × (1 + waste)
BlindingV = (bottom + 2 × projection) × thickness × length
Side formworkS = 2 × side length × total length
Sloping lengthL = √(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.

How to work it out

  1. Pick the section formula: rectangular A = base width × depth; trapezoidal A = (top + bottom) ÷ 2 × depth.
  2. Concrete V = section area × total length × (1 + waste). Strip footings keep a constant section along their run, which makes them the simplest class to measure.
  3. Formwork is sides only: rectangular 2 × depth × length; trapezoidal on the batter, with slope length L = √(depth² + ((base − top) ÷ 2)²).
  4. Blinding = (base width + 2 × projection) × thickness × length, with a 100 mm projection each side.
  5. Base area = base width × total length, used for the bearing check.

Where it goes wrong

Material and cost

C25-C30 concrete runs 400-500 per m³, formwork 45-70 per m², C15 blinding 350-420 per m³. Cost per metre of strip footing is a common shortcut for scheme estimates: 300-600 per m for housing, depending on depth and ground conditions.

On site

Basis

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.

Cite this page

Use this format in reports, method statements or coursework. The link is permanent.

Building Calculator. Strip Footing Calculator. 2026-10-25. https://jianzhujisuan.com/en/strip-footing

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.