How To Calculate Quantity of Cement and Sand in Plaster
Following points should be remembered while calculating the quantity of cement, sand for plastering work.
1. For wall plastering, Cement : Sand = 1 : 6
2. For ceiling plastering, Cement : Sand = 1 : 4
3. Thickness of plaster should be in between 12-15 mm. If an additional coat is required then do not do it at one go.
4. Use good quality of cement & Sand.
5. Use measuring box (not head pan) for site mix.
We will calculate cement and sand for 100 m2 plastering area in 1:6 ratio and thickness of 12 mm.
Cement Mortar Required:
Plastering thickness = 12 mm
= 12/1000 = 0.012m
Volume of cement mortar required = ( Plastering Area x thickness )
= 100 m2 x 0.012m = 1.2 m3
(This is wet volume of cement mortar (after mixing water) but we need dry volume. To get dry volume consider 35% bulking of sand and 20% wastages
= 1.2 m3 x (1+0.2+0.35) (Rather than 35% sand bulkage and 20% wastage you can add 1.54 as constant)
= 1.86 m3
Cement : Sand = 1 : 6
Sum of ratio =( 1 + 6) = 7
∴ Cement required
= 1.86 x 1/7
= 0.265 m3
= 0.265/0.0347 ( 0.0347 m3 = 1 bag = 50 kg cement)
= 7.66 bags (≈ 8 Bags)
∴ Sand required
= 1.86 x 6/7
= 1.59 m3
Here we have calculated in Sq.m but you can also calculate it in Sq.ft.