How Much Cement, Sand and Aggregate for Concrete?

Slab, footing, or column — once you know the wet volume of concrete, the rest is arithmetic. This guide walks through how Indian estimators split that volume into cement bags, sand (cft), and aggregate (cft), and how to ballpark the material cost before you call the supplier.

What you need

Three dimensions (or the volume if you already have it):

1. Length
2. Width
3. Depth / thickness

Plus the concrete grade from your drawing — M20 for many house slabs, M25 for heavier loads, M15 or M10 for lean concrete (PCC) under floors.

Keep units consistent. Convert feet and inches to metres (or work entirely in feet) before multiplying.

Step 1: Wet volume

Wet volume = length × width × depth

Example: a 3 m × 3 m slab, 100 mm (0.1 m) thick.

Wet volume = 3 × 3 × 0.1 = 0.9 m³ (~31.8 cft)

That is the space the finished concrete fills — not the loose pile of sand and stone you order.

Step 2: Dry volume (× 1.54)

Materials are measured dry. Site practice multiplies wet volume by 1.54:

Dry volume = wet volume × 1.54

For 0.9 m³: 0.9 × 1.54 = 1.39 m³ dry volume

The 1.54 factor covers voids between particles, shrinkage when water is added, and a small wastage allowance. Without it, you under-order every time.

Step 3: Split by mix ratio

Each grade has a fixed nominal ratio (cement : sand : aggregate by volume):

| Grade | Ratio | Total parts | |-------|-------|-------------| | M10 | 1 : 3 : 6 | 10 | | M15 | 1 : 2 : 4 | 7 | | M20 | 1 : 1.5 : 3 | 5.5 | | M25 | 1 : 1 : 2 | 4 | | M30 | 1 : 0.75 : 1.5 | 3.25 |

For M20 (common for residential slabs):

• Cement = dry volume × (1 ÷ 5.5) = 1.39 × 0.182 ≈ 0.25 m³
• Sand = dry volume × (1.5 ÷ 5.5) ≈ 0.38 m³
• Aggregate = dry volume × (3 ÷ 5.5) ≈ 0.76 m³

Step 4: Convert to bags and cft

Indian cement bags are 50 kg. At ~1440 kg/m³ bulk density, one bag ≈ 0.0347 m³.

Cement bags = ceil(cement m³ ÷ 0.0347)

0.25 ÷ 0.0347 ≈ 7.2 → 8 bags

Sand and aggregate are usually ordered in cft from local suppliers:

cft = m³ × 35.3147

• Sand: 0.38 × 35.3 ≈ 13.4 cft
• Aggregate: 0.76 × 35.3 ≈ 26.8 cft

Step 5: Rough material cost

Cost is not fixed — it moves by city, season, and haul distance. A simple first pass:

Cost ≈ (bags × ₹/bag) + ((sand cft + aggregate cft) × ₹/cft)

If cement is ₹400/bag and sand/aggregate combined rate is ₹55/cft:

8 × 400 + (13.4 + 26.8) × 55 ≈ 3,200 + 2,210 ≈ ₹5,410 for materials only

Steel, shuttering, labour, and pump hire are all separate. This number is for ordering cement, sand, and stone — not turnkey slab cost.

Worked summary (3 m × 3 m × 100 mm, M20)

| Item | Value | |------|--------| | Wet volume | 0.9 m³ (~31.8 cft) | | Dry volume (×1.54) | 1.39 m³ | | 50 kg cement bags | 8 bags | | Sand | ~13 cft | | Aggregate | ~27 cft | | Rough material cost | ~₹5,000–6,000 (rates vary) |

Skip the manual math — use our Cement Sand Aggregate Calculator to get this instantly. Enter dimensions in m or ft, pick M10–M30, edit ₹/bag and ₹/cft to match your local rates.

When to use this vs the slab calculator

Both tools overlap for a simple rectangular slab. Use this calculator when you want sand and aggregate broken out separately with editable per-material rates, or when the shape is still a box but the job is a footing, column, or beam rather than a floor slab. For a quick slab estimate with a ready-mix ₹/m³ cost range, see how to calculate cement for a slab.

Practical tips

• Round cement bags up, never down.
• Confirm the grade on the structural drawing — do not swap M20 for M25 without engineer approval. See M20 vs M25 if you are comparing.
• Order sand and aggregate from a supplier who can deliver separate stacks on site — mixing ratios go wrong when materials are short.
• Add 5–10% extra on irregular shapes, steps, or uneven shuttering.

FAQ

Can I use this for a footing or column?

Yes. Any rectangular wet volume works: footing length × width × depth, or column as a square/rectangle in plan × height. Irregular shapes: break into boxes, add volumes, then apply 1.54 and the grade ratio.

Why is aggregate almost double the sand for M20?

The nominal mix 1:1.5:3 gives aggregate twice the sand volume (3 vs 1.5 parts). That matches how lean the mix is on site — concrete is mostly stone, not cement.

Does this include steel and labour?

No. This is material quantity and a material-only cost hint. RCC slab cost on site is often 60–70% labour, steel, and formwork, with materials as one line item.

M15 vs M20 — how much difference in bags?

For the same volume, M15 (leaner) uses fewer cement bags than M20 because cement is a smaller fraction of the mix. Always match the drawing grade; saving bags by downgrading grade is not safe.

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Want the cement-only shortcut for slabs? Read how to calculate cement for a slab. Browse all construction guides, or compare grades in M20 vs M25 concrete.