Enter the member size in feet and inches, pick the grade, and get cement in 50 kg bags with sand and aggregate in cubic feet and brass — computed by the standard 1.54 dry-volume method.
The method, in the open
dry volume = length × width × thickness × 1.54
The dry volume is split in the nominal mix proportions — M15 = 1:2:4, M20 = 1:1.5:3, M25 = 1:1:2 (cement : sand : aggregate). Cement volume converts to bags at 34.7 litres per 50 kg bag; sand and aggregate convert to cubic feet, and to brass at 100 cft per brass — the unit most Indian suppliers actually quote.
Worked example — 10 ft × 10 ft × 5″ slab
That slab is 1.18 m³ wet, 1.82 m³ dry. In M20 it needs about 9.5 bags of cement, 17.5 cft of sand and 35 cft (0.35 brass) of aggregate. The calculator defaults show this exact slab.
Nominal mix vs design mix
These quantities are for nominal mixes, the ratio-based batching used on small residential sites. Larger structures use designmixes proportioned in a lab for a target strength. If your drawings specify a design mix or ready-mix concrete (RMC), follow the engineer's batching, and use this page only to sanity-check order quantities.
Frequently asked questions
How many cement bags are needed for 1 m³ of M20 concrete?
About 8 bags of 50 kg cement per cubic metre of M20 (1:1.5:3) by the nominal-mix method, together with roughly 15 cft of sand and 30 cft of aggregate.
What does the 1.54 dry-volume factor mean?
Dry cement, sand and aggregate compact when mixed with water — voids between particles fill up. To end with 1 m³ of placed concrete you must batch about 1.54 m³ of dry material, so every nominal-mix calculation starts by multiplying wet volume by 1.54.
Which grade should I use — M15, M20 or M25?
As a rule of thumb on small residential jobs: M15 for levelling courses and non-structural beds, M20 for slabs, beams and columns of ordinary houses, M25 where the structural engineer asks for it. The grade for any structural member is the engineer's decision, not a calculator's.
How much does 1 brass of sand or aggregate weigh?
One brass is 100 cubic feet. Dry river sand runs about 4.5–5 tonnes per brass and crushed aggregate about 4.2–4.8 tonnes, varying with moisture and gradation — suppliers bill by volume precisely because weight varies.
Reviewed on 15 August 2026. These are preliminary planning quantities from standard methods — actual consumption varies with workmanship, wastage and site conditions. VastuCalc does not provide structural design; sizes, grades and reinforcement must come from a qualified engineer.