About this calculator
This calculator takes off the materials for column (pad) footings: identical rectangular concrete pads, each carrying a square or round pier. It gives the concrete for the pads and piers, the blinding under the pads, the formwork area, and the reinforcement (pad mesh, pier bars and ties) with the number of stock bars to buy.
Lay the footings out in one of three ways:
- Grid — columns × rows at a centre-to-centre spacing in each direction;
- Around a building perimeter — a footing at every corner, then along each side at no more than the maximum spacing (the same rule as the pile foundation calculator);
- Number of footings — just a count, when the layout is irregular.
It is a quantity take-off only. The pad size, founding depth and reinforcement are your inputs, taken from the structural design — the calculator checks none of them against loads or the ground.
Formula
For one footing with pad A × B × H and pier size C, height P:
pad concrete = A × B × H
pier concrete = C² × P (square)
= π/4 × C² × P (round)
blinding = (A + 2o) × (B + 2o) × t o = projection, t = thickness
pad formwork = 2 × (A + B) × H (when the pad sides are formed)
pier formwork = 4 × C × P (square)
= π × C × P (round, the tube surface)
Totals are one footing × the number of footings; the waste % is added to the concrete.
Number of footings: grid = columns × rows; perimeter = 2 × (ceil(L / S) + ceil(W / S)).
Reinforcement (c = cover, d = bar diameter):
pad bar along A = A − 2c
pad bar along B = B − 2c
pier bar = (H − c_pad − 2 d_pad) + P − c_pier + leg
tie (square) = 4 × (C − 2 c_pier − d_tie) + 20 d_tie
tie (round) = π × (C − 2 c_pier − d_tie) + 20 d_tie
ties per pier = floor((P − 2 c_pier) / spacing) + 1
bar mass = length × π/4 × d² × 7850 kg/m³ (LST EN 10080, 7.3.2)
Stock bars are counted by packing every cut piece of the same diameter into stock lengths (first-fit decreasing).
Worked example
A 3 × 2 grid (6 footings), pads 1000 × 1000 × 300 mm, square piers 300 × 300 mm, 1200 mm high, 50 mm blinding projecting 100 mm, 5% waste. Pads: 6 + 6 bars Ø12, cover 50 mm. Piers: 4 bars Ø12 with a 300 mm leg, cover 40 mm, Ø6 ties at 200 mm.
pad = 1.0 × 1.0 × 0.3 = 0.300 m³
pier = 0.3 × 0.3 × 1.2 = 0.108 m³
6 footings = 6 × 0.408 = 2.448 m³ + 5% = 2.570 m³ to order
blinding = 1.2 × 1.2 × 0.05 × 6 = 0.432 m³
formwork = 6 × (2 × 2.0 × 0.3) + 6 × (4 × 0.3 × 1.2) = 7.20 + 8.64 = 15.84 m²
pad bars = 1000 − 100 = 900 mm, 72 bars, 64.8 m × 0.888 kg/m = 57.5 kg
pier bars = 300 − 50 − 24 + 1200 − 40 + 300 = 1686 mm, 24 bars = 40.5 m → 35.9 kg
ties = 4 × (300 − 80 − 6) + 120 = 976 mm, 6 per pier, 36 ties = 35.1 m → 7.8 kg
steel in total ≈ 101.3 kg; stock bars: 10 × Ø12 and 4 × Ø6 of 11.7 m
FAQ
How deep should a column footing be? Its underside should normally be below the design frost depth at the site, unless the ground is not frost-susceptible or the footing is insulated against frost. The frost depth calculator gives Lithuanian figures with their sources. The structural engineer decides the final depth from the geotechnical report.
How big should the pad be and how much steel does it need? That depends on the load on the column and the bearing capacity of the ground, which this calculator does not know. Enter the pad size and reinforcement from your structural design.
Why is there a separate blinding volume? Blinding (a thin lean concrete layer under the pad) is usually ordered as a lower-strength mix and poured first, so it is kept apart from the footing concrete.
Can a round pier be cast in a tube? Yes — round piers are usually cast in cardboard or plastic formwork tubes. The parts list gives one tube per pier at the pier height.
Which standard does this follow? LST EN 206 for the concrete class designation, LST EN 10080 (clause 7.3.2) for the nominal mass of reinforcing bars, and LST EN 1992-1-1 (4.4.1.3(4)) for the two cover warnings: a recommended minimum cover of 40 mm on blinding or prepared ground and 75 mm when the pad is cast directly against soil. The sizes and the reinforcement themselves are a structural design matter (Eurocode 2 and Eurocode 7), which this calculator does not perform.
Assumptions and limits
- Every footing is the same: one pad size, one pier size and one reinforcement layout.
- The grid is regular; a perimeter layout follows a rectangular outline with footings on its centrelines, oriented with A along the building length. Internal footings in perimeter mode are not added — use the count mode for an irregular layout.
- Pad reinforcement is a single bottom mesh. Pier bars are L-shaped: a straight vertical plus a leg into the pad; bends, laps, top mesh, spacers and tie wire are not counted. Ties carry a 20 × diameter hook allowance (trade practice).
- Formwork is the contact area of the pad sides (when formed) and the pier; no board count.
- A pier bar's leg must fit inside the pad: half the smaller pad side, less the pad cover, less the bar's offset from the pier axis; a longer leg is an error.
- No excavation, backfill or concrete mass is calculated (see the excavation calculator).
- The default sizes, covers, spacings and the 11.7 m stock bar are examples, not design values.