For standard UK blocks (440 × 215mm face) with 10mm mortar joints, whatever their thickness.
Page last reviewed 26 October 2026 by the UkToolCalc team
10 blocks per m² of wall. Buy about 11 per m² to allow 5% for cuts. This is the same for 100mm, 140mm and 215mm blocks, because the face size is the same.
Thicker blocks need the same count but more mortar and are much heavier to move. The block calculator handles dense and aircrete blocks in every thickness.
Frequently asked questions
Why exactly 10 blocks per m²?
A 440 × 215mm block with 10mm joints takes up 450 × 225mm of wall, which is 0.10125m², so 9.88 blocks per m². The trade rounds it to 10.
How heavy are 100 concrete blocks?
100mm dense blocks weigh about 19.5kg each, so 100 blocks are nearly 2 tonnes. Aircrete blocks of the same size are about 7kg each.
How much mortar per m² of blockwork?
About 20kg of dry mortar per m² of 100mm blockwork: roughly 16kg of building sand and 4kg of cement in a 4:1 mix.
