Free construction calculators for the site

How the concrete mix calculator works

Enter a volume in cum or cft and pick the nominal mix grade — M7.5 (1:4:8), M10 (1:3:6), M15 (1:2:4), M20 (1:1.5:3) or M25 (1:1:2). The calculator applies the standard dry-volume factor of 1.54 and splits the dry volume across the mix ratio, giving cement in 50 kg bags (one bag ≈ 0.0347 cum), sand and aggregate in cft, and approximate water at w/c ≈ 0.5. For M25 and above on structural work, follow your lab's mix design sheet — nominal ratios are for estimation and small pours.

Steel weight calculator: the d²/162 rule

Rebar weight per metre is d²/162 kg, where d is the bar diameter in mm — the standard formula used on every Indian site and in every bar bending schedule. A 12 mm bar weighs 12²/162 ≈ 0.89 kg/m; a full 12 m length ≈ 10.7 kg. Enter the diameter (6 to 32 mm), length and number of bars to get the total weight in kg, plus bars per tonne — handy for checking a steel challan against what was ordered. For member-wise cutting lengths and a full schedule, see the BBS calculator.

Brickwork: bricks, cement and sand

For a wall's length, height and thickness, the calculator uses the standard figure of ~500 modular bricks per cum of brickwork and splits the mortar (about 30% of wall volume, with a dry factor) across your chosen cement:sand ratio — 1:4, 1:5 or the common 1:6. You get bricks, cement bags and sand in cft, which is usually what the supplier quotes against.

Plaster quantities

Give the area (sqm or sqft), plaster thickness in mm (12 mm internal, 15–20 mm external are typical) and the mortar ratio. The calculator adds the standard allowance for surface undulation and dry volume, and returns cement bags and sand — so a plastering rate quoted "with material" can be checked in a minute.

When the site needs more than a calculator

These tools answer one question at a time. The SiteHisab app keeps the whole hisab: a BOQ register built from published Schedule-of-Rates items, quantity estimates read from your structural drawings by AI, daily labour and material entries, RA bills with GST and TDS, and project money in one place. Every new subscriber gets a 14-day free trial.