Free UK construction calculators Metric and imperial 2026 UK prices
Work out the concrete, the steel cage and the formwork for round, square or rectangular concrete columns. Enter the size, the number of columns and the bars, press Calculate, and see the cubic metres, the main bars and links, the tie wire, the column formers or plywood, and the cost, with quick checks against the usual detailing rules.
Concrete Needed
0m³
Check the measurements above. The result updates once they look right.
| Method | What To Order | Cost |
|---|
Typical 2026 UK prices including VAT. Ready-mix includes a 1 m³ minimum and the part-load charge under 4 m³.
| Item | Cost |
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Labour, cutting and bending, and pump hire are extra.
You get the concrete in cubic metres with three ways to buy it, the main bars and links with their lengths and weight, the tie wire, the column formers or plywood, and the material cost. A drawing shows the column and a section through the cage, and six quick checks flag anything outside the usual detailing limits.
| Column | Area | Concrete per metre | Weight per metre |
|---|---|---|---|
| Ø 200 mm round | 0.031 m² | 31 litres | 75 kg |
| Ø 250 mm round | 0.049 m² | 49 litres | 118 kg |
| Ø 300 mm round | 0.071 m² | 71 litres | 170 kg |
| Ø 400 mm round | 0.126 m² | 126 litres | 302 kg |
| 200 × 200 mm square | 0.040 m² | 40 litres | 96 kg |
| 250 × 250 mm square | 0.063 m² | 63 litres | 150 kg |
| 300 × 300 mm square | 0.090 m² | 90 litres | 216 kg |
| 400 × 400 mm square | 0.160 m² | 160 litres | 384 kg |
Multiply by the height and the number of columns. Four 300 mm square columns 2.4 m high need 4 × 0.09 × 2.4 = 0.86 m³, or about 0.9 m³ with 5% extra. A round column holds about 21% less concrete than a square column of the same width.
A reinforced concrete column has vertical main bars, which carry load with the concrete, and links (also called ties or stirrups), which wrap round the main bars and stop them buckling outwards. The cage sits inside a layer of concrete called the cover, which protects the steel from rust and fire.
At the bottom, the main bars lap onto starter bars cast into the foundation. The calculator adds a lap of 40 bar diameters to each main bar, which is 640 mm for an H16 bar; your engineer may ask for a different lap. Each link includes about 24 link diameters for its hooks. For a full cutting list, or for slabs and walls, use our rebar calculator.
| Rule | Usual limit |
|---|---|
| Number of main bars | At least 4, one in each corner; usually 6 or more in a round column |
| Main bar size | At least 12 mm in the UK |
| Link size | At least 6 mm and a quarter of the main bar size |
| Link spacing | No more than 20 × the smallest main bar, the column width or 400 mm, whichever is least |
| Steel area | Between about 0.2% and 4% of the column section |
| Cover | Typically 30–40 mm, 50 mm or more against the ground |
These are the common detailing limits from Eurocode 2 and its UK National Annex, which the calculator checks. Passing them does not mean a column is strong enough: that depends on the load, the height and the concrete, and needs a structural engineer.
| Bar | Weight per metre | Typical use in columns |
|---|---|---|
| H8 | 0.395 kg | Links |
| H10 | 0.617 kg | Links for bigger bars |
| H12 | 0.888 kg | Main bars in small columns |
| H16 | 1.579 kg | Main bars in most house columns |
| H20 | 2.466 kg | Main bars in heavier columns |
| H25 | 3.854 kg | Main bars in large columns |
Bar weight is 0.00617 × diameter² kg per metre. Bars are sold in stock lengths of 6 m or 12 m, or cut and bent to a schedule. Ready-made links save time on site.
Round columns are usually cast in spiral-wound cardboard column formers. They come in 3 m lengths in diameters from about 150 mm up, are cut to height, braced plumb, then peeled off once the concrete has set. They are single-use, so the calculator counts one per column, or more for columns over 3 m.
Square and rectangular columns are usually boxed in 18 mm shuttering plywood, clamped and braced. The calculator works out the plywood area from the column's outside edge × height × number of columns, plus 10% for cutting. Good plywood boxes can be reused several times, so the cost for many columns may be lower than shown. Our concrete formwork calculator covers boxing for slabs, footings and steps.
Structural columns are normally specified as C25/30 or C32/40, which is best bought as ready-mix with a certificate. For small piers and posts that are not structural, a site mix of 1 part cement to 4 parts all-in ballast is a strong general mix. Columns hold little concrete, so a few small columns often fall below a ready-mix minimum load; the calculator compares ready-mix, mixing on site and 20 kg bags so you can see the cheapest.
| Item | Typical 2026 UK price |
|---|---|
| Ready-mix concrete, per m³ | £100–£160, plus part-load under the minimum |
| H16 rebar, per metre | £4–£6 |
| H8 links, per metre | £1.50–£2.50 |
| Cardboard column former, 3 m | About £45–£150, by diameter |
| 18 mm shuttering plywood sheet | £40–£55 |
| Tie wire, 1 kg roll | £5–£8 |
Former prices vary a lot between suppliers and diameters, so the calculator's default is only a guide; enter your own quote. Labour, cutting and bending, cranes or pumps are not included.
Columns hold up beams, floors and roofs, so they come under Part A of the Building Regulations. A structural engineer should size the column, its bars and links, and its foundation, and Building Control will usually want to see the calculations and inspect the steel before you pour. The government's Approved Document A explains the structural requirements. Use this calculator to price and order materials from an engineer's design, not to design the column.
Concrete = section area × height × number of columns × (1 + extra %) · Round area = 3.1416 × diameter² ÷ 4
Main bar length = height + 40 × bar diameter · Links per column = height ÷ spacing + 1, rounded down then plus one
Link length = cage perimeter inside the cover + 24 × link diameter · Steel (kg) = metres × 0.00617 × d²
Ties are one per crossing of a main bar and a link, at about 250 ties per kilogram of wire. Concrete for site mixing uses a dry volume of 1.25 × the wet volume, cement at 1,440 kg/m³ and ballast at 1.7 t/m³, the same as our concrete calculator. Ready-mix is ordered in 0.25 m³ steps, charged at a 1 m³ minimum, with your part-load charge below 4 m³.
Section area × height. A 300 mm square column 2.4 m high holds 0.3 × 0.3 × 2.4 = 0.216 m³. A 300 mm round column the same height holds 0.170 m³.
At least four, one in each corner of a square or rectangular column. Round columns usually have six or more. The engineer sets the actual number and size.
Main bars are at least 12 mm in the UK, and H16 is common in house columns. Links are often H8, and must be at least a quarter of the main bar size.
Under Eurocode 2 and the UK National Annex, no more than 20 times the smallest main bar, the least width of the column, or 400 mm, whichever is smallest. That is 320 mm for H16 bars.
Typically 30–40 mm to the links for columns above ground, and 50 mm or more where concrete is cast against the ground. The engineer sets it for the exposure.
Structural columns are usually C25/30 or C32/40 ready-mix. For small non-structural piers, a site mix of 1:4 cement to all-in ballast is suitable.
Stand a cardboard column former over the starter bars, drop the cage inside, brace it plumb, then fill it in lifts while vibrating. Strip the tube after a few days.
Yes, for any column that carries a building. The engineer designs it, and Building Control approves the design and inspects the work.
Detailing limits follow Eurocode 2 (BS EN 1992-1-1) and its UK National Annex. Bar weights use 0.00617 × d² kg/m. Concrete figures match the rest of ConstructionMath. Default prices are typical 2026 UK prices including VAT; column former prices vary widely, so check with your supplier. Reviewed November 2026.