Concrete Mix Ratios and Quantity Estimation: How Many Bags of Cement, Sand, and Gravel per Cubic Meter

By Engr. Ruel H. Cepeda, Structural Engineer

Before cement is delivered to site, someone has to answer a simple question: how many bags, how much sand, how much gravel? In the Philippines, that answer starts with a "class of mixture" — AA, A, B, or C — a cement:sand:gravel ratio by volume, paired with an estimating table that converts a member's volume into bags and cubic meters of aggregate. This article covers those classes, the table behind them, the dry-volume logic behind the numbers, and three worked examples — a slab, a footing, and a column.

The Four Philippine Concrete Classes

Philippine construction practice settled on four volumetric mix classes, written cement : sand : gravel — a trade convention popularized by Philippine estimating handbooks (note that the DPWH Standard Specifications define their own Class A/B/C/P by minimum cement content and strength, which is a different scheme) rather than an NSCP 2015 / ACI 318-19 mix design, which specifies concrete by target f’c and water-cementitious ratio instead.

These strength figures are rules of thumb, not guaranteed by mixing alone — actual strength depends on water content, aggregate quality, and mixing control, and should be confirmed by mix design and cylinder testing.

The Standard Estimating Table (Materials per Cubic Meter)

For quick take-offs, Philippine estimators use a commonly cited table giving the 40 kg cement bags, sand, and gravel needed per cubic meter of finished concrete for each class — an estimating table for pricing and ordering, not a laboratory mix design.

Notice sand and gravel stay at 0.5 m³ and 1.0 m³ across every class — only cement changes. That's because all four ratios reduce to the same 1:2 sand-to-gravel split (1.5:3, 2:4, 2.5:5, and 3:6 are identical), so richer mixes simply add more cement to the same aggregate volume.

Where These Numbers Come From: The Dry-Volume Method

The estimating table is a rounded version of the dry-volume method: loose materials settle into a smaller volume once mixed and compacted, so estimators multiply wet concrete volume by a bulking factor — commonly 1.54 — to get the dry volume to batch:

V_dry = V_wet × 1.54

That dry volume then splits among cement, sand, and gravel by the mix ratio's parts. For Class A (1:2:4, parts summing to 7), applied to 1.0 m³ of finished concrete:

• Dry volume: 1.0 × 1.54 = 1.54 m³ (ratio parts 1 + 2 + 4 = 7).
• Cement: volume = (1/7) × 1.54 = 0.220 m³; weight at 1,440 kg/m³ = 316.8 kg; bags (40 kg) = 316.8 ÷ 40 ≈ 7.9 bags.
• Sand: (2/7) × 1.54 = 0.440 m³.
• Gravel: (4/7) × 1.54 = 0.880 m³.

This "raw" figure lands below the 9.0-bag trade-table value for Class A (7.92 ÷ 9.0 = 0.88, i.e. about 12% lower, and the same 12% gap on the sand and gravel lines: 0.44 vs 0.5 m³ and 0.88 vs 1.0 m³). That's not an error — the job-site table already folds in an allowance for spillage, compaction loss, and rounding up to whole bags. Use the trade table for ordering; the dry-volume method explains it and covers a ratio not already tabulated.

40 kg Bags vs. 50 kg Bags

Philippine suppliers package cement in 40 kg bags, lighter than the 50 kg standard in many neighboring countries. Since the figures above are on a 40 kg basis, converting to 50 kg bags is a straight weight ratio (multiply by 40/50 = 0.8):

As a rough reference, a 40 kg bag occupies about 0.028 m³ and a 50 kg bag about 0.035 m³ (assumed cement density ≈ 1,440 kg/m³). The 50 kg column above is the pure arithmetic conversion; some published trade tables round it slightly differently (roughly 9.5, 7.0, 6.0, and 5.0 bags), so quote the table you are actually using. Convert first when pricing imported cement or a foreign 50 kg reference — mixing bag sizes in one take-off is a common source of a 20–25% cement error.

From Member Volume to Material Order: Adding Wastage

The estimating table gives quantities per cubic meter of finished concrete. To turn a member into a shopping list: compute its volume, multiply by the class table's per-m³ figures, then add a wastage allowance before rounding up to whole bags. This article applies 5% wastage on cement (mainly spillage, since bags round up anyway) and 10% on sand and gravel (more loss to spillage and segregation during hauling) — adjust to your own site conditions.

Worked Example 1 — Slab, 100 mm Thick, 4 m × 5 m, Class A

• Step 1 — Volume: 4.0 m × 5.0 m = 20.0 m²; 20.0 m² × 0.100 m = 2.0 m³.
• Step 2 — Base quantities (Class A: 9.0 bags, 0.5 m³ sand, 1.0 m³ gravel per m³): Cement = 9.0 × 2.0 = 18.0 bags. Sand = 0.5 × 2.0 = 1.0 m³. Gravel = 1.0 × 2.0 = 2.0 m³.
• Step 3 — Apply wastage: Cement = 18.0 × 1.05 = 18.9 → round up to 19 bags. Sand = 1.0 × 1.10 = 1.10 m³. Gravel = 2.0 × 1.10 = 2.20 m³.

Worked Example 2 — Isolated Footing, 1.5 m × 1.5 m × 0.40 m, Class A, 6 Footings

• Step 1 — Volume of one footing: 1.5 m × 1.5 m = 2.25 m²; 2.25 m² × 0.40 m = 0.90 m³.
• Step 2 — Total volume, 6 footings: 0.90 × 6 = 5.40 m³.
• Step 3 — Base quantities: Cement = 9.0 × 5.40 = 48.6 bags. Sand = 0.5 × 5.40 = 2.70 m³. Gravel = 1.0 × 5.40 = 5.40 m³.
• Step 4 — Apply wastage: Cement = 48.6 × 1.05 = 51.03 → round up to 52 bags. Sand = 2.70 × 1.10 = 2.97 m³. Gravel = 5.40 × 1.10 = 5.94 m³.

Worked Example 3 — Column, 400 mm × 400 mm × 3.0 m, Class AA, 8 Columns

• Step 1 — Volume of one column: 0.40 m × 0.40 m = 0.16 m²; 0.16 m² × 3.0 m = 0.48 m³.
• Step 2 — Total volume, 8 columns: 0.48 × 8 = 3.84 m³.
• Step 3 — Base quantities (Class AA: 12.0 bags, 0.5 m³ sand, 1.0 m³ gravel per m³): Cement = 12.0 × 3.84 = 46.08 bags. Sand = 0.5 × 3.84 = 1.92 m³. Gravel = 1.0 × 3.84 = 3.84 m³.
• Step 4 — Apply wastage: Cement = 46.08 × 1.05 = 48.384 → round up to 49 bags. Sand = 1.92 × 1.10 = 2.11 m³. Gravel = 3.84 × 1.10 = 4.22 m³.

Running these by hand across many members is repetitive — the free RHCE Tools spreadsheets on the download page carry this logic in one pass, and the sister site's BOQ estimator on RHCES is a good second check.

Assumptions & Limitations

• The Class AA–C ratios and estimating table are a trade convention for volumetric batching, not an NSCP 2015 / ACI 318-19 mix design, which instead specifies concrete by target f’c and water-cementitious ratio verified by trial batches.
• Table quantities are per cubic meter of finished, in-place concrete — not loose dry materials.
• Cement bag figures assume standard 40 kg bags; convert before using a 50 kg reference or imported cement.
• The dry-volume factor (1.54) and cement density (1,440 kg/m³) are common assumed values; actual density varies by brand.
• Wastage allowances (5% cement, 10% sand/gravel) are typical planning figures, not a code requirement — adjust to site conditions.
• These figures size material orders only, not structural design or strength verification against the specified f’c.

Frequently Asked Questions

Are the Class AA/A/B/C ratios an official NSCP 2015 or ACI 318 mix design method?

No. NSCP 2015 and ACI 318-19 specify concrete by target f’c and water-cementitious ratio, verified by trial batches and cylinder testing. The volumetric classes here are a trade convention for pricing and minor works batched by gauge box — structural members need a proper mix design from the engineer of record.

Why do the sand and gravel quantities stay the same across all four classes while only cement changes?

Because all four ratios reduce to the same 1:2 sand-to-gravel split (1.5:3, 2:4, 2.5:5, 3:6 are identical). The table holds that split at 0.5/1.0 m³ per cubic meter and lets cement carry the difference between a lean Class C and a rich Class AA mix.

Should I add wastage to the cement bag count, or just buy exactly what the table says?

Add an allowance. Crews lose cement to spillage, and any fractional bag count rounds up anyway since a bag can't be split. A 5% cement and 10% sand/gravel allowance is reasonable for ordinary conditions; long hauls or inexperienced crews warrant more.

Getting the mix class and quantity take-off right avoids a mid-pour cement run. Browse the free calculators on RHC Engineering's WebTools page, or grab the offline spreadsheets from the download page for site use without internet.