cement sand stone of stone 1 2 3 16 0.5 0.8 1 2.5 4 13 0.5 0.8 1 3 5 11 0.5 0.9 *Slab thickness in mm. 3. Decide whether to use: (a) Premix concrete from a readymix supplier (b) Bagged cement, sand and stone (c) Bagged concrete Estimating how much cement, sand and stone to order The Ready Reckoner for concrete is a general guide only.