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Concrete Formwork Calculator

Estimate the edge-form board footage and surface area needed to contain a concrete slab pour.

Computed in your browser — nothing you enter is uploaded. Figures are presented in United States units and terminology, and each formula’s basis is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax
13 ft10 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Form boards needed

7 x 8 ft boards

Check your inputs

This estimates edge-form board footage only — it doesn't include stakes, bracing, or release agent, and assumes a simple rectangular pour with no interior forms or curves.

Formwork surface area
15.33 sq ft
Perimeter (with waste)
50.6 linear ft

For the dimensions entered, expect a form boards needed of 7 x 8 ft boards. Moderate confidence — sound arithmetic, but allow for the variation any real site introduces. Set for United States. The market selector changes the units and the trade terminology; any standard behind the formula is cited under sources.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.

Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Regulatory standards & verification citations

  • Formwork surface area = perimeter x form height (2 x [length + width] x thickness); board count = perimeter / stock board length, with a waste allowance for stakes and cuts

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Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Frequently asked questions

Why does form board height need to match slab thickness?
The form's job is to hold wet concrete in place until it cures — if the board is shorter than the slab thickness, concrete will spill over the top edge during the pour.
Do I need stakes too?
Yes — forms are held in place with stakes driven into the ground roughly every 2-3 ft along the form, a small separate material not included in this board-footage estimate.
Can I reuse formwork boards for future projects?
Yes, especially if you avoid nailing directly through them and coat them with a release agent (like vegetable oil or a commercial form-release product) to prevent concrete from bonding to the wood.