350 kg of cement per m³, the usual reinforced-concrete mix, with 0.4 m³ of sand and 0.8 m³ of gravel.

How is the steel weight calculated?

By d²/162, in kilos per metre. A 12 mm bar weighs 0.888 kg a metre.

Should I order a margin?

Cement is rounded up to whole bags. For the rest, keep a margin: being 5% short stops the pour and leaves the crew standing.

Volume for a slab, footing or column, the cement / sand / gravel split, and the weight of the steel.

Length (m)

Width (m)

Thickness (m)

Diameter (mm)

Total length (m)

A 350 kg/m³ mix, standard for reinforced concrete. Check your engineer's specification before ordering.