Footing concrete is measured in cubic units, while formwork is usually planned from the surface that touches the fresh concrete. A footing can have the same volume but a different formed area when its length, depth, free ends, earth contact or pour sequence changes.
List the physical faces before applying a perimeter formula. Count each side, end, step, key or blockout only when form sheathing will contact that face during the stated pour.
How do you calculate footing formwork area?
Multiply the length of each formed face by its vertical or sloping contact dimension, then add the face areas. For a rectangular footing with all 4 vertical faces formed, multiply the perimeter by the formed depth.
Rectangular footing contact area = 2 × (length + width) × formed depth × quantity
Strip contact area = [2 × length × formed depth + formed ends × width × formed depth] × quantity
The top is normally open for placement and finishing. The bottom usually bears on accepted ground, rock, blinding or another surface. Exclude either face unless physical form sheathing contacts it.
A geometric face belongs in the quantity only when the planned form system creates that concrete surface at the stated construction stage.
Which faces belong in a footing formwork schedule?
| Face | Include when | Exclude when |
|---|---|---|
| Long side | Form sheathing contains the fresh concrete along that side | The approved concrete is cast directly against ground, rock or existing work with no form |
| Free end | A stop-end or end board closes the concrete section | The run continues into monolithic concrete with no physical stop form |
| Top | A top form physically contains an approved sloping, closed or special surface | The top remains open for placement and finishing |
| Bottom | A suspended or specially supported bottom form physically contacts the concrete | The footing bears on accepted ground, rock, blinding or existing concrete |
| Step riser | A vertical or sloping step face uses a form | The face is cast against an accepted excavated or permanent boundary |
| Shared interface | A construction-stage stop form separates pours | Connected concrete is placed monolithically without a form at the interface |
| Key, rebate or blockout | A formed insert creates the specified surface | The feature is absent or produced by another approved method without contact sheathing |
Record the drawing, detail, pour stage and boundary decision beside every exception. A final square-metre or square-foot total cannot show which physical faces were assumed.
How do you calculate strip-footing side and end forms?
Calculate the 2 long faces separately from the free ends. The width affects the end area, but it does not affect the area of the long side faces.
A 12 m strip footing is 0.60 m wide and 0.30 m deep. Both long sides and both free ends use forms:
- First long side: 12 × 0.30 = 3.600 m².
- Second long side: 12 × 0.30 = 3.600 m².
- Two ends: 2 × 0.60 × 0.30 = 0.360 m².
- Total contact area: 3.600 + 3.600 + 0.360 = 7.560 m².
| Formed face group | Calculation | Area |
|---|---|---|
| 2 long sides | 2 × 12 × 0.30 | 7.200 m² |
| 2 free ends | 2 × 0.60 × 0.30 | 0.360 m² |
| Total | 7.200 + 0.360 | 7.560 m² |
Use the Strip Footing Length guide to confirm whether the entered run is a centreline, outside, inside or clear length. Formwork needs the actual length of each contact face, not an unlabelled foundation perimeter.
How do you calculate pad-footing formwork area?
For a rectangular pad with all 4 vertical faces formed, multiply its concrete perimeter by the formed depth. Multiply the unrounded area by the number of pads only when their geometry and face conditions are identical.
Six pad footings each measure 1.80 m by 1.40 m by 0.45 m:
- One pad perimeter: 2 × (1.80 + 1.40) = 6.40 m.
- One pad contact area: 6.40 × 0.45 = 2.880 m².
- Six pads: 2.880 × 6 = 17.280 m².
Combining these pads with the 7.560 m² strip fixture gives 24.840 m² of cumulative contact area. That sum does not state how much reusable formwork must be owned or rented at one time.
Worked imperial example: 4 rectangular pads
Four identical pads measure 4 ft by 3 ft with a formed depth of 14 in. All 4 vertical faces use forms.
| Stage | Calculation | Result |
|---|---|---|
| Depth conversion | 14 ÷ 12 | 1.166666667 ft |
| One pad perimeter | 2 × (4 + 3) | 14 ft |
| One pad area | 14 × 1.166666667 | 16.333333 ft² |
| Four pads | 16.333333 × 4 | 65.333333 ft² |
Keep the unrounded depth through the multiplication. Rounding 1.166666667 ft to 1.17 ft before calculating would show 65.52 ft², adding 0.186667 ft² to this small fixture.
What changes when one side is cast against earth?
Remove the face from the formwork schedule only when the approved construction method places concrete directly against an accepted ground or rock boundary and no sheathing occupies that face.
If one 12 m long side of the metric strip is earth-contact and the other side plus 2 ends are formed, the contact area becomes:
- One long side: 12 × 0.30 = 3.600 m².
- Two ends: 0.360 m².
- Total formed contact: 3.960 m².
The excluded side is 3.600 m², but excavation volume and concrete volume may still change if the earth boundary is irregular. Use the Footing Excavation vs Concrete Volume guide to keep those boundaries separate.
Loose soil, collapse, water, unsuitable bearing material or an unapproved enlarged face needs field resolution. A contact-area deduction cannot approve concrete placement against that condition.
Do connected footing runs need end forms?
Count an end only where a physical form stops the concrete during that pour. A strip that continues into a pad, crossing or another strip can have no formed end at the shared monolithic interface.
| Connection | Contact-area treatment | Record needed |
|---|---|---|
| Free strip end | Add width × depth | End location and formed dimensions |
| Monolithic strip into pad | Exclude the internal interface when no stop form exists | Pour plan and connected geometry |
| Construction joint between pours | Add the actual stop-end contact face for the applicable pour | Joint detail, pour ownership and any key or waterstop forms |
| Strip crossing placed together | Trace the external boundary; do not add 4 internal ends | Plan union and section depths |
| Existing concrete interface | Exclude where new concrete contacts existing work without a form | Interface preparation and actual limits |
Calculate the union of the concrete plan when several runs meet. Then identify the external vertical boundary and any real internal stop forms. Adding a 2-end formula to every schedule line can place fictional forms inside monolithic concrete.
How do stepped footings change the area?
Split the long sides at every depth change. Add a step riser only when physical form sheathing creates that surface.
A stepped strip has Section A at 6 m long, 0.60 m wide and 0.25 m deep. Section B is 4 m long, 0.60 m wide and 0.40 m deep. Both long sides and the 2 outside ends are formed.
| Face group | Calculation | Area |
|---|---|---|
| Both long sides | 2 × [(6 × 0.25) + (4 × 0.40)] | 6.200 m² |
| Section A free end | 0.60 × 0.25 | 0.150 m² |
| Section B free end | 0.60 × 0.40 | 0.240 m² |
| Optional formed bottom riser | 0.60 × (0.40 - 0.25) | 0.090 m² |
| Total with formed riser | 6.200 + 0.150 + 0.240 + 0.090 | 6.680 m² |
If the 0.090 m² riser is cast against an accepted permanent or excavated boundary with no form, exclude it and record 6.590 m². If the step has a slope, key, haunch or changed width, measure its actual contact geometry.
How should sloping and curved faces be measured?
Use the true contact length along the face. A sloping face needs its slant dimension, and a curved face needs the applicable arc length, not a straight plan chord.
Sloping rectangular face area = face run × slant height
Vertical cylindrical face area = circumference × formed height
Break a compound face into shapes whose dimensions can be verified. Battered, trapezoidal, circular, combined and irregular footings can require drawing, model or survey geometry beyond the rectangular schedule used by the Concrete Footing Calculator.
Do keys, rebates and blockouts add formwork area?
Add the surfaces created by a form insert, box-out or stop-end, then subtract any base face that the feature replaces when the takeoff method requires net contact area.
For a rectangular recess, list its vertical sides and its closed top or bottom contact separately. A timber insert can use more material than its net contact area because it also needs thickness, joints, fixing and extraction clearance.
Do not infer key or blockout dimensions from the footing size. Use the current detail and preserve the feature ID so the quantity can be revised without altering unrelated faces.
Is contact area the same as plywood sheet quantity?
Contact area is the concrete surface touched by the form facing. Sheet procurement also depends on available panel sizes, grain or strength direction, joints, cut layout, repeated dimensions, edge losses, holes, damage, stripping sequence and permitted reuse.
Gross sheet quotient = contact area ÷ gross sheet face area
The quotient is only a lower-bound area comparison. It does not include offcuts, panel orientation, support spacing, ties, stakes, walers, braces, corners, release agent, fasteners, labour or design loads.
ACI describes formwork as the contact mold or sheathing plus the supporting members, hardware and bracing. A square-metre takeoff covers only one part of that system.
How does form reuse change the required set area?
Separate cumulative contact area from the maximum area that must be formed at the same time. Reusable panels can serve several pours only when the approved sequence allows stripping, cleaning, repair and re-erection before the next pour.
| Quantity | Meaning | Example use |
|---|---|---|
| Cumulative contact area | Sum of all formed concrete faces across the work | Takeoff, productivity or payment record under its stated rules |
| Pour-group contact area | Faces needed for one scheduled placement | Set preparation and inspection |
| Maximum simultaneous area | Largest total held in active or strength-gain stages at one time | Initial system quantity planning |
| Gross panel face area | Nominal reusable facing area available | Layout input before cuts and exclusions |
| Net usable panel area | Area remaining after layout, damage and system constraints | Procurement or rental check |
The 24.840 m² metric contact total could require 24.840 m² of simultaneous facing if the strip and all pads are formed together. A sequenced plan could need less reusable face area, but only after timing, strength, stripping, access, inspection and panel compatibility are confirmed.
How should contact area be checked against concrete volume?
Use the same footing marks and dimensions in both schedules, but compare the results as different units. Concrete volume is length × width × depth. Side-form area is face length × formed depth.
| Field | Concrete schedule | Formwork schedule |
|---|---|---|
| Footing mark | Identifies the concrete solid | Identifies its formed faces |
| Length and width | Set plan volume | Set side and end lengths |
| Depth | Sets concrete thickness | Sets vertical contact height where formed |
| Count | Repeats identical solids | Repeats only identical face conditions |
| Intersection | Removes duplicated concrete volume | Removes internal faces without forms |
| Earth contact | May change accepted concrete boundary | Removes the applicable contact face when no form is used |
The Concrete Footing Volume guide explains strip, pad, step and intersection solids. Match its section IDs to the formwork schedule instead of deriving one quantity from a generic volume-to-area ratio.
What should a footing formwork takeoff record contain?
- Project, footing mark, drawing, detail, model and revision.
- Pour group, sequence, planned joint and existing-work interface.
- Concrete length, width, depth, count and units.
- Every formed side, end, top, bottom, riser, slope, key, rebate and blockout.
- Earth-contact, existing-concrete, monolithic-interface and open-face exclusions.
- Unrounded face areas, exclusion areas and net contact total.
- Cumulative area, pour-group area and maximum simultaneous set area.
- Selected form system, panel layout, cut plan, reuse assumption and supplier record.
- Design, inspection, release, stripping, repair and acceptance records.
Common footing formwork quantity mistakes
- Multiplying concrete volume by a generic m²-per-m³ ratio.
- Counting the open top and supported bottom as formed faces.
- Adding 2 ends to every connected strip section.
- Counting an internal monolithic interface as 2 formed faces.
- Using centreline length for both side faces without checking their actual paths.
- Ignoring changed depths, risers, keys, rebates and blockouts.
- Removing an earth-contact face without confirming the approved method and actual condition.
- Multiplying a cumulative contact total directly into whole plywood sheets.
- Assuming every panel can be reused through every pour.
- Using one pad count when face conditions differ by location.
- Rounding each face before the schedule is added.
- Using a quantity result to design or approve formwork.
What safety and design limits apply?
Contact-area arithmetic does not design a form system. For covered U.S. construction work, OSHA 29 CFR 1926.703 requires formwork to support reasonably anticipated vertical and lateral loads and addresses jobsite plans, inspections and removal conditions within its scope.
Form design and erection depend on concrete pressure, placement rate, temperature, vibration, member geometry, materials, ties, anchors, stakes, walers, braces, bearing, wind, equipment, access and qualified design. Follow the current drawings, specifications, form-system information, applicable rules and responsible people.
Forms and shores must remain until the required removal conditions are met. A reuse plan cannot set stripping time from contact area or a desired production date.
Return to the Concrete Planning hub for published footing, concrete-supply, reinforcement and joint resources.
Sources and source scope
- American Concrete Institute, ACI Resources: Formwork for Concrete: formwork definition, contact sheathing, supporting members, hardware, bracing and formwork purpose.
- ACI SP-004: (8TH) Formwork for Concrete: current ACI formwork reference scope and alignment with ACI 347R-14.
- OSHA 29 CFR 1926.703: covered U.S. formwork load, plan, inspection and removal requirements.
- Penn State architectural engineering structural takeoff: one project example recording concrete volume and formwork contact area as separate quantities.
- NIST Handbook 133 (2026), Appendix E: length and area unit relationships used in the fixtures.
Source scope: ACI supports the formwork-system and contact-sheathing distinction. OSHA supports the cited U.S. workplace boundary. The Penn State report is one project example, and NIST supports unit arithmetic. These sources do not set this page's independent face formulas as a payment rule, choose a form system, provide a universal material factor, design the forms, set reuse, or approve stripping.
Review note: Saleem Sial owns the research and editorial record. Formula fixtures, source checks, build validation and rendered QA form the internal publication gate. Waseem Sial, External Reviewer and Engineer, is listed for ongoing external review; no completed review date is claimed.
