Material quantities per IS 456:2000Table 9 — shown in the code's actual mass basis, alongside the conventional 1:2:4-style equivalents sites have batched for decades.
Route 1 —
bags cement
Route 2 —
bags ·
IS 456 Table 9 prescribes nominal mixes by mass: total dry aggregate per 50 kg of cement (M5: 800 kg → M20: 320 kg), fine-to-coarse aggregate 1:2 by mass (adjust 1:1½–1:2½ for grading and MSA), and a maximum water content per 50 kg (60 L at M5 down to 30 L at M20). Route 1 converts that batch to per-m³ quantities by absolute volume (cement 3.15, aggregate 2.65 specific gravity).
Route 2 converts the familiar 1:5:10 … 1:1½:3 ratios with the usual 1.54 dry-volume factor. For M5–M10 the two agree closely. For M15 and M20 the conventional ratios run noticeably richer in cement than Table 9 — a real divergence you should know about when comparing estimates. We show both rather than quietly pick one.
Verified against IS 456:2000 (AMD 5) — see our verified constants table.
Given: M20, 1 m³, FA:CA 1:2.
Route 1 (Table 9): one batch = 50 kg cement + 320 kg agg + 30 L water → 0.167 m³ → per m³: 300 kg cement (6 bags), FA 640 kg, CA 1280 kg, water ≤ 180 L.
Route 2 (1:1½:3): dry 1.54 m³ → cement 0.28 m³ = 8.1 bags, sand 0.42 m³, CA 0.84 m³.
IS 456 Cl 9.3 permits nominal (recipe) mixes only up to M20, and only for minor plain works. M25+ needs a designed mix proportioned per IS 10262:2019 for your actual materials — that is what the CMD App does.
In principle IS 456 restricts nominal mixes to plain concrete minor works. Design mixes are preferred for everything structural; site-batched 1:1½:3 "M20" for RCC is a legacy practice, not a code endorsement.
The 1:1½:3 ratio descends from old volume-batched recipes and, converted by mass, sits at about 400 kg/m³ cement versus Table 9's roughly 300 kg/m³. Table 9 is the code's prescription; the ratio is the tradition. For structural work neither replaces a designed mix.
Often used together with this calculator — pick the next step in your design or QA loop.
Deep dive: read the full significance guide — the code clauses, assumptions and site meaning behind these numbers.