Shuttering calculator for slabs, beams, columns and footings
This shuttering calculator works out the formwork contact area — the concrete surface that touches the shuttering — for every member of a pour: slabs, beams, rectangular and circular columns, footings and walls. Add a line for each member type with its sizes and how many there are, and it totals the area in m² and sq ft, the plywood sheets needed with a cutting allowance, an estimate of props under slabs and beams, and the cost at your contractor’s rate per sq ft or m².
Shuttering is usually measured and paid by contact area, so the same figure answers “how much plywood do I need?” and “what will the centring and shuttering cost?”. A table under the calculator gives the IS 456 minimum striking times for each kind of formwork.
It is a quantity estimate. The formwork system and the props must be designed by a competent engineer for the weight of wet concrete and construction loads.
How to use the Shuttering Calculator
- Choose metric or imperial units.
- For each member line, pick the type (slab, beam, column, circular column, footing or wall), enter the sizes and how many identical members there are. Use Add member for more lines.
- Untick Include slab edge forms if the slab edges sit on beams or walls instead of side shutters.
- Choose the plywood sheet size and cutting waste, the prop spacing from your falsework design, and your shuttering rate.
- Read the total area, sheets, props and cost; copy the summary or download the table as CSV.
Shuttering Calculator features
Contact-area formulas per member
Slab soffit plus edges, beam sides and bottom below the slab, column perimeter × height, π × diameter × height, footing sides, and both wall faces plus ends.
Plywood sheets
Total area plus waste divided by the sheet size — 8 × 4 ft, 6 × 3 ft, 2500 × 1250 mm or your own.
Props estimate
Props so that no gap between props, or between a prop and a support, exceeds the spacing you set.
IS 456 striking times
Clause 11.3.1 minimum periods for vertical forms, slab and beam soffits and props.
Shuttering calculator formula for each member
Worked example: one 4 × 3 m slab, two beams, four columns and four footings give 13.75 + 7.04 + 16.32 + 10.8 = 47.91 m², or 515.7 sq ft. With 10% cutting waste that is 52.7 m² of 8 × 4 ft plywood (2.977 m² a sheet), so 18 sheets. Props at 1.2 m: the slab needs 3 × 2 = 6 and each 4 m beam 3, so 12 in all.
| Member | Shuttering area | Example |
|---|---|---|
| Slab | L × W + 2(L + W) × t (edges) | 4 × 3 m, 125 mm: 12 + 1.75 = 13.75 m² |
| Beam | L × (b + 2 × (D − slab thickness)) | 4 m, 230 × 450, 125 slab: 3.52 m² |
| Column (rectangular) | 2(b + d) × h | 230 × 450, 3 m: 4.08 m² |
| Column (circular) | π × D × h | 300 mm, 3 m: 2.83 m² |
| Footing | 2(L + B) × depth (sides only) | 1.5 × 1.5 × 0.45 m: 2.7 m² |
| Wall | 2 × L × H + 2 × t × H | 5 × 3 m, 200 mm: 31.2 m² |
Column shuttering and beam shuttering: what to watch
- A beam cast with the slab needs side shutters only below the slab soffit, so the slab thickness is taken off each side. A beam cast on its own (lintel, plinth beam) needs 0 for slab thickness.
- Column formwork is the full perimeter times the height to the beam or slab soffit. Measure the height from the top of the footing or floor to the underside of the beam.
- Footings cast in trimmed earth may need no side forms; footings above ground need all four sides. The sloped top of a trapezoidal footing is usually left unformed.
- Openings, chamfers, kickers and stair waists are not included — add them as extra lines.
Plywood, props and reuse
Film-faced plywood is reused for several pours, so the sheet count here is for the area of one pour. Prop numbers depend on prop capacity, slab thickness and the bearers used; take the spacing from your falsework design or the prop supplier’s load table. IS 14687 gives guidelines for falsework. For the concrete volume use the concrete calculator, and for the reinforcement the steel quantity calculator.
Shuttering Calculator FAQ
What is the formula for shuttering area?
Shuttering area is the concrete surface in contact with the forms. For a slab it is length × width plus the edges; for a beam, length × (width + 2 × depth below the slab); for a column, perimeter × height. The shuttering calculator adds them for you.
How do you calculate column shuttering?
Multiply the column perimeter by its height: 2 × (0.23 + 0.45) × 3 m = 4.08 m² for a 230 × 450 mm column 3 m high. A circular column is π × diameter × height.
How many plywood sheets do I need for shuttering?
Divide the shuttering area plus a cutting allowance by the sheet area. An 8 × 4 ft sheet covers 2.977 m² (32 sq ft), so 50 m² with 10% waste needs 19 sheets.
When can shuttering be removed?
IS 456 clause 11.3.1 gives minimums for ordinary Portland cement above 15 °C: 16–24 hours for column, wall and beam sides, 3 days for slab soffits and 7 days for beam soffits with props refixed, 7–14 days for slab props and 14–21 days for beam props.
Is shuttering measured in sq ft or m²?
Both are used; Indian contractors often quote per sq ft and drawings use m². This tool shows both.