Concrete Mix Ratios — 1:2:4, 1:1.5:3, and 1:1:2 by Strength
Nominal volumetric mixes are still the working language of small and mid-size Philippine projects. Knowing what each ratio delivers — and costs — is basic estimating literacy.
Ratio to strength class
| Nominal mix (C:S:G) | Approx. strength | Typical use |
|---|---|---|
| 1:3:6 | ~13.8 MPa (2000 psi) | Lean concrete, fill, blinding |
| 1:2:4 | ~20.7 MPa (3000 psi) | Slabs on grade, footings, general RC |
| 1:1.5:3 | ~24.1 MPa (3500 psi) | Suspended slabs, beams |
| 1:1:2 | ~27.6 MPa (4000 psi) | Columns, high-load members |
Materials per m³ (1:2:4)
Cement = 1.54 / (1+2+4) × 1 = 0.22 m³ ≈ 6.3 bags (40 kg) — use 7–7.5 with waste
Sand = 0.22 × 2 = 0.44 m³
Gravel = 0.22 × 4 = 0.88 m³
Richer mixes climb fast: 1:1:2 needs about 11–12 bags of cement per m³ versus 7–7.5 for 1:2:4 — a real cost difference across a column-heavy structure.
When to leave nominal mixes behind
- Strength above ~28 MPa, or where the spec calls for a characteristic strength with statistical acceptance.
- Durability requirements (exposure class, low permeability, sulfate resistance).
- Pumped concrete, self-compacting concrete, or tight workability windows.
Then a designed mix from a batching plant, specified by strength class and slump, replaces the volumetric ratio.
EngEst Pro lets you pick the mix per structural element and computes cement bags, sand, and gravel per cubic metre with wastage — the Structural Calculator rolls it into the concrete line items in your BOQ.
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