Concrete Calculator
Concrete volume plus cement, sand, and crush quantities by mix ratio
Frequently Asked Questions
Concrete quantity estimation in Pakistan follows the standard dry-volume method — wet (poured) concrete volume is multiplied by a 1.54x factor to get the dry material volume needed, since cement, sand, and aggregate lose volume as they combine and compact, and skipping this factor systematically underestimates every material quantity.
Why dry volume isn't the same as wet volume
When cement, sand, and crushed stone (aggregate) are mixed with water and poured, the combined wet volume ends up smaller than the sum of the loose dry ingredients, because the finer particles fill the voids between the coarser ones. The standard correction factor — 1.54x — converts a target wet (poured) volume back to the dry material volume that needs to be purchased and mixed, and this factor is applied before splitting the total into cement, sand, and aggregate according to the chosen mix ratio (for example 1:2:4 for standard slab and foundation work, or 1:1.5:3 for higher-strength columns and beams). A cement bag is conventionally treated as 1.25 cft of loose volume for this calculation, which is how the bag count is derived from the cement portion of the dry volume.
A worked example
A slab poured to a specific wet volume requires purchasing a noticeably larger dry material volume than the poured figure alone would suggest — anyone ordering materials based on the wet (finished) volume without applying the 1.54x factor will run short partway through the pour, which is both a costly delay and a structural risk if a pour gets interrupted partway.
How this connects to your other construction planning
This is the general-purpose concrete mix calculator — for a roof slab specifically, with steel reinforcement included alongside the concrete mix, use the dedicated Roof Slab Calculator, which applies the same dry-volume logic but adds rebar weight on top. For overall project cost across every material category at once, see the Construction Cost Calculator.
Common mistakes
Beyond forgetting the dry-volume factor entirely, a common mistake is applying the wrong mix ratio for the structural element being poured — using a low-strength 1:3:6 mix ratio intended for flooring or PCC on a structural column or beam undermines strength where it matters most, so always confirm the mix ratio your structural engineer specifies for each specific pour rather than defaulting to whichever ratio was used elsewhere on the same site.