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Formwork Brace & Kicker Force Calculator

The axial load in a wall-form brace (kicker) from the lateral pressure on its tributary strip, and the horizontal and vertical reactions at its anchor.

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Full height of the form panel that the lateral pressure acts against.

Measure the panel, not the pour. A form standing taller than the concrete still catches wind over its whole height, and on a windy site that is often the case that governs the kicker rather than the concrete pressure.

Centre-to-centre spacing of the kickers, which is also the width of form tributary to one of them.

Every kicker carries the strip of form halfway to its neighbours in each direction, so the tributary width equals the spacing for a regular run. An end brace with no neighbour on one side carries less; a brace either side of a gap carries more, and neither case is covered by a uniform spacing.

Lateral load per unit of form face, taken from the governing construction-loads document.

This is a bracing load, not the concrete's own lateral pressure on the sheathing — the two are separate checks and the bracing one is usually a wind or code-minimum case. ACI 347R and ASCE/SEI 37 between them set the floor and the wind case; use whichever the job is being reviewed against, and the larger of the two where both apply.

Angle the kicker makes with the slab it bears on, measured at the anchorage.

A steep kicker takes a much larger axial load for the same horizontal push, and it dumps a correspondingly larger vertical component into the anchor. A shallow one is gentler on both but needs floor space the job may not have. Somewhere near 45 to 60 degrees is the usual compromise, and the arithmetic here shows exactly what each degree costs.

Height above the base of the form at which the kicker connects to it.

The lower the connection, the larger the force in the brace, because the same overturning moment is being resisted on a shorter lever arm. Attaching near the top of the panel is almost always the efficient choice; attaching at mid-height doubles the brace load.

Axial force in the brace

1.13 kips

Medium confidence

This is one brace resolved by statics. Whether the slab can take it is a separate anchor check against the concrete's age and strength on the day, the embedment available, and the edge distance at the fixing — a young slab is the usual weak link, not the kicker.

Total lateral force on the braced strip
0.9 kips
Horizontal reaction at the anchorage
0.56 kips
Vertical reaction at the anchorage
0.98 kips
Lateral force per unit length of form
150.38 lbf/ft
Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

  • ACI 347R, Guide to Formwork for Concrete, is the document that sets the minimum lateral force wall-form bracing must be designed for; the pressure used here is the one you enter from it, not a figure this page supplies
  • ASCE/SEI 37, Design Loads on Structures During Construction, governs the construction-stage wind and lateral load cases that produce that pressure
  • OSHA 29 CFR 1926 Subpart Q requires formwork to be designed, erected, supported, braced and maintained so that it supports all vertical and lateral loads applied to it
  • Statics only: uniform lateral pressure over the tributary strip, the form taken as pinned at its base, and the resultant resolved along a kicker at the angle entered

Inputs used

Form Height
10 ft
Brace Spacing Along the Form
6 ft
Design Lateral Load on the Form Face
15.04 psf
Brace Angle to Horizontal (degrees)
60
Brace Attachment Height
8 ft

Intermediate steps

Total lateral force on the braced strip
0.9 kips
Horizontal reaction at the anchorage
0.56 kips
Vertical reaction at the anchorage
0.98 kips
Lateral force per unit length of form
150.38 lbf/ft
Final result1.13 kips

Confidence note: This is one brace resolved by statics. Whether the slab can take it is a separate anchor check against the concrete's age and strength on the day, the embedment available, and the edge distance at the fixing — a young slab is the usual weak link, not the kicker.

What this calculation does not cover

  • Single-sided bracing on a form pinned at its base; a form braced from both faces, or one restrained at the base by a kicker plate, distributes the load differently.
  • Does not check the brace member itself for buckling, nor its end connections — a compression kicker at this angle is often governed by slenderness rather than by axial capacity.

Add the equipment this sizes

This result is a specification — 1.13 kips — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

10 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Computed in your browser — nothing you enter is uploaded. 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.

Sources checked 2026-08-30 · in the site-wide review of 2026-09-06 · v1.0.0

Regulatory standards & verification citations4
  1. ACI 347R, Guide to Formwork for Concrete, is the document that sets the minimum lateral force wall-form bracing must be designed for; the pressure used here is the one you enter from it, not a figure this page supplies
  2. ASCE/SEI 37, Design Loads on Structures During Construction, governs the construction-stage wind and lateral load cases that produce that pressure
  3. OSHA 29 CFR 1926 Subpart Q requires formwork to be designed, erected, supported, braced and maintained so that it supports all vertical and lateral loads applied to it
  4. Statics only: uniform lateral pressure over the tributary strip, the form taken as pinned at its base, and the resultant resolved along a kicker at the angle entered

Which documents these citations point at

Standards referenced: ACI 347R (American Concrete Institute, United States).

Cite this page

Your workspace

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.

Tools and safety for this job

To erect formwork. Generic types, no brands, no prices.

Protection this work requires

  • Hardwood dust is a recognised carcinogen: extract at the tool and wear a P2/N95 respirator when cutting or sanding indoors.
  • Saws, grinders and breakers run above 85 dB, where hearing damage accumulates and does not recover: defenders or plugs for every cut, not just the long ones.
  • Boards, blocks and bagged material cause most lasting back injuries on small sites: two people or a lifter for full sheets, and never a bag on one shoulder up a ladder.
Show the 6 tools this job needs

Essential

  • Circular saw

  • Claw hammer

  • Spirit level

  • String line and pins

  • Tape measure

Recommended

  • Cordless drill/driver

Also needed as materials: circular saw blades, drill and driver bits.

what each concrete tool is for, and the spec that decides which to buy where one does.

Now that you have the number

These guides cover the work this quantity is for — the first ones run this calculator inside the section that raises the question.

Called something else where you work? Adjustable props and shoring — the term in each market, how close the equivalence really is, and the standard that governs it.

How to calculate formwork brace & kicker force in 6 steps

  1. Form HeightFull height of the form panel that the lateral pressure acts against.
  2. Brace Spacing Along the FormCentre-to-centre spacing of the kickers, which is also the width of form tributary to one of them.
  3. Design Lateral Load on the Form FaceLateral load per unit of form face, taken from the governing construction-loads document.
  4. Brace Angle to Horizontal (degrees)Angle the kicker makes with the slab it bears on, measured at the anchorage.
  5. Brace Attachment HeightHeight above the base of the form at which the kicker connects to it.
  6. Axial force in the braceThe tool computes the axial force in the brace from those figures and shows the formula, its sources, and a confidence rating alongside it.

Frequently asked questions

Is the concrete's lateral pressure the load I should enter here?
Usually not. The concrete's pressure is what sizes the sheathing, studs, walers and ties — it acts inward on the form face and is largely balanced by the ties. What the kicker resists is the load that would push the whole assembly over: wind on the exposed face, workers and plant leaning on it, and the code minimum that applies when neither is large.
Why does attaching the brace lower down make the force so much worse?
Because the overturning moment stays the same while the lever arm resisting it gets shorter. The wind or code load acts at mid-height of the panel whatever you do; halving the height at which the kicker connects doubles the horizontal reaction it has to develop, and the axial force follows straight along with it.
What does the vertical reaction actually do to the slab?
It presses down where a compression kicker bears and lifts where a tension brace pulls, and at 60 degrees it is nearly twice the horizontal component rather than a small side effect. On a young slab or a thin topping, that vertical component is frequently what governs the anchor rather than the shear.
Does this cover a form braced from both sides?
No. Two-sided bracing shares the lateral load between the two systems and changes the base condition assumed here, so running this once per side would overstate both. Treat the result as the single-sided case, which is the arrangement most site kickers actually are.
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.