Pile Cap Calculator — m, m³, rebar
How to use this calculator
A pile cap ties a group of bored or driven piles together and spreads the column load over the whole group. Enter the cap shape, number of caps, plan size in m/cm/mm, depth, and pile count — the diagram updates with pile positions and a cross-section. Cap depth drives punching shear and column-bar anchorage, so most caps land between 600 mm and 1 200 mm.
Cost — ready-mix per m³, 50 kg bags, or 25 kg bags.
Reinforcement — bottom mat with bars in both directions per EC2 §9.8.1, 75 mm cover over piles.
Labor — rate per cap, per m³, or flat price.
Saved Calculations
| Time | Caps | Size | Piles | Vol m³ | Cost | Rebar | Labor | Total |
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How to Calculate Concrete for Pile Caps (Metric)
A pile cap ties a group of bored or driven piles or piers together and spreads a column or grade-beam load over the whole group. Enter the plan size in m, cm, or mm, the cap depth, and the pile count. Cap thickness is governed by one-way and punching shear and by anchorage of the column starter bars — roughly 600 mm for a 2-pile cap, 900 mm for a 4-pile cap, and 1 200 mm+ for heavily loaded 6- or 9-pile groups. Volume is the gross rectangular block; pile heads embed only ~75–100 mm and are ignored.
How to use it
Choose square or rectangular, set the number of identical caps, then enter width, length, and depth. Enable the optional cost, reinforcement, and labour panels as needed — the grand total sums only the enabled panels, and the currency selector covers EUR, GBP and other European currencies. Size the columns above with the grade beam calculator and the slab over the caps with the slab calculator.
Reinforcement per EN 1992-1-1 (Eurocode 2)
EC2 §9.8.1 treats a pile cap with a strut-and-tie model: the principal reinforcement is a bottom mat both ways, concentrated over the piles, with 75 mm nominal cover and full anchorage beyond the inner face of the outer piles. This tool reports bars each way at the chosen spacing (Ø12–Ø20 B500B at 100–250 mm) and adds a percentage for lap splices (40·Ø) and cutting waste. Confirm bar anchorage and minimum steel against your engineer's tie model before ordering.
Formulas
Volume = Width × Length × Depth × Caps × (1 + Waste%) in m³. Mass ≈ Volume × 2 400 kg/m³. Bars each way = (span − 2 × cover) ÷ spacing + 1; total length = (nW·W + nL·L) × Caps × (1 + lap/waste%); bar mass uses 0.888, 1.578, 2.466 kg/m for Ø12/Ø16/Ø20.
FAQ
How thick should a pile cap be? Depth is set by shear and by the anchorage length of the column bars hooked into the cap, commonly 1.5–3× the pile diameter and never less than the required anchorage. Use the depths above as starting points only.
Do I deduct the pile embedment? No. Piles project only ~75–100 mm into the cap; the displaced volume is negligible and conventionally ignored, so this calculator uses the gross block.
Bagged or ready-mix? Almost all pile caps exceed 1 m³ and should be ready-mixed; 50 kg / 25 kg bag modes (≈0.024 / 0.012 m³ each) are only for cross-checking small isolated caps with the concrete bag calculator. Where piles are not required, compare with a spread footing or a strip footing for continuous wall loads.
On pour day
Three things estimators forget on pile-cap pours. Pile cut-off level — confirm every pile is trimmed 75–100 mm into the cap before the cage drops; an over-cut pile means field-welded rebar extensions, an under-cut pile means breaking concrete back. Column starter bars — set the column dowels in a plywood template before the pour so they are plumb and on the column grid; misplaced dowels cost more than the cap concrete. Short-load and pump — a 1.8×1.8×0.9 m cap is ~2.9 m³, so most plants charge a short-load fee under 3 m³ and €250–500 for a line pump if access is tight. Ready-mix C25/30 runs roughly €110–160/m³ in 2025 Europe; Ø16 B500B lands near €1.80–2.80/m installed. EC2 §9.8.1 (strut-and-tie / mat reinforcement) and §8.4 (bar anchorage into the cap) govern — keep the structural drawing on site.
