TryBuildCalcFloor Slab Concrete Calculator (RCC Volume, Cement, Sand & Aggregate)
Calculate slab concrete volume and materials.
Estimate floor slab concrete volume, cement bags, sand, and aggregate. Adjust slab dimensions, thickness, mix ratio, and wastage for your RCC estimate.
🕒 Last updated: August 6, 2026
Inputs
ℹ️Typical: 100–150 mm
Optional Deductions
Deduct staircase openings, ducts, lift shafts, or other voids from the slab area before calculating concrete volume.
Cost
Concrete Volume: 12.000 m³ / 423.8 cft
Wet Volume: 12.000 m³ / 423.8 cft
Dry Volume: 18.480 m³ / 652.6 cft
Sand: 5.280 m³ / 186.5 cft
Aggregate: 10.560 m³ / 372.9 cft
Cement Required (Including 5% Wastage): 80 bags
Extra (Wastage): 3.80 bags
Planning the shuttering and prop layout for this slab? Slab Shuttering Process Guide →
Approximate results for planning only. Verify with a professional.
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete Concrete Slab Calculator.
Floor slab concrete estimate
This page is set up for a larger floor slab with a 100 mm thickness.
The calculator is pre-filled for this slab use case. Edit any input and the worked example updates from the active values.
- Default size: 12 m x 10 m.
- Thickness: 100 mm.
- Mix ratio: 1:2:4.
How does the concrete slab calculator work?
The calculator follows standard civil engineering formulas to estimate concrete volume and material quantities step-by-step, from the net slab area down to cement bags.
Step 1 — Calculate Net Slab Area
For a single rectangular slab this is just Length × Width. Multiple Sections sums each rectangle (for L-shaped/irregular footprints); Optional Deductions subtracts any staircase, duct, or void areas.
Step 2 — Calculate Wet Volume
Step 3 — Convert to Dry Volume
The factor 1.54 accounts for voids, bulking of sand, and material losses during mixing.
Step 4 — Calculate Material Proportions
Step 5 — Convert Cement Volume to Bags
Step 6 — Add Wastage
Step 7 — Cost (Optional)
All three quantities are priced at their wastage-adjusted amount. Sand and aggregate prices can be entered per m³ or per cft — whichever unit you enter is converted to match automatically.
Worked Example: Concrete Slab Calculation
This example uses the active inputs above and follows the same steps as the Formula section.
Input Values Used
| Input | Value |
|---|---|
| Length × Width | 12 m × 10 m = 120 m² |
| Thickness | 100 mm (0.1 m) |
| Concrete Mix | M15 (1:2:4) |
| Wastage | 5% |
Step 1 — Net Area & Wet Volume
| Calculation | Substitution | Result |
|---|---|---|
| Net Area = Gross − Openings | 120 − 0 | 120 m² |
| Wet Volume = Net Area × Thickness | 120 × 0.1 | 12 m³ / 423.8 cft |
Step 2 — Dry Volume
| Calculation | Substitution | Result |
|---|---|---|
| Dry Volume = Wet Volume × 1.54 | 12 × 1.54 | 18.48 m³ / 652.6 cft |
Step 3 — Materials & Cement Bags
| Material | Share of Mix (1:2:4) | Result |
|---|---|---|
| Sand | 2 / 7 | 5.28 m³ / 186.5 cft |
| Aggregate | 4 / 7 | 10.56 m³ / 372.9 cft |
| Cement Bags (with 5% wastage) | 1 / 7 | 80 bags |
Therefore, this slab needs approximately 12 m³ / 423.8 cft of concrete, requiring 80 cement bags, 5.28 m³ / 186.5 cft sand, and 10.56 m³ / 372.9 cft aggregate (including 5% wastage on cement).
Cross-check against the Standard Concrete Mix Ratios table in the complete Concrete Slab Calculator.