Craft Quantities
Plan & Takeoffs

By trade

Concrete calculators

Concrete is ordered by volume and almost every mistake starts with an area. The pour, the steel in it and the shutter around it scale differently from each other: double a slab's length and the volume and the mesh double, the perimeter does not, and the thickening under a wall does not move at all.

  • 56Calculators
  • 3Parts of the site

How concrete is measured

Cubic metres for the pour, tonnes or metres for the reinforcement, square metres of contact face for the formwork — and the pour is the only one of the three that a supplier will refuse to part-deliver. Bagged mixes are a fourth unit again: a bag's yield is a volume of finished concrete, not a weight of powder.

Where concrete sits on this site56 across 3
56

Materials & Quantities53

Sustainability & Compliance2

Heavy Civil & Infrastructure1

What gets left off a concrete order

  • The thickenings: a slab with a perimeter beam or a load-bearing wall under it holds far more concrete than its nominal thickness suggests.
  • Over-dig and uneven ground. Concrete poured against excavated faces takes what the ground gives it, which is always more than the geometry.
  • The waste from part-loads. Ordering 7.3 m³ means taking 7.5, and the extra is paid for whether it is placed or not.
  • Curing: blankets, compound or water for days after the pour, which is labour and material nobody puts on the concrete line.

Job takeoffs8

Where concreters meet the rest of the job: each runs one of these calculators, with every other trade in the same job beside it.

Worked examples4

A real job estimated step by step, with this trade's steps counted.

Comparisons22

Two ways of doing the same work, weighed against each other.

Planners2

Work this trade out from a space rather than from a job.