TryBuildCalcRaft Foundation Cost CalculatorRaft foundation cost estimator
Calculate concrete, two-way mesh steel, and shuttering quantity for an RCC raft (mat) foundation.
🕒 Last updated: August 12, 2026
Raft Dimensions
ℹ️Overall raft footprint length, usually the building's outer plan dimension.
ℹ️Rafts are typically 300-1000+ mm thick depending on soil bearing capacity and building load — confirm from the structural drawing.
Concrete
ℹ️Foundation cover is typically higher than a suspended slab's — commonly 50 mm or more, confirm against your applicable code and exposure class.
Bottom Mesh (resists upward soil pressure)
Top Mesh (resists hogging near columns)
Lap Splices
Shuttering
Cost
Please enter a valid shuttering rate
Enter the raft dimensions and reinforcement details to calculate concrete, steel, and shuttering quantities.
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete Raft / Mat Foundation Calculator.
Raft foundation cost estimate
This page pre-selects cost estimation, so concrete cost (rate × final volume), steel cost (rate × total weight), and shuttering cost (rate × contact area, if included) are all shown together with a combined total.
Edit the rates above to match your local supplier and labour pricing — the underlying concrete, steel, and shuttering quantities are calculated exactly the same way as the main calculator.
- Concrete cost = final wastage-adjusted volume × your entered rate per m³ (or per cft).
- Steel cost = total mesh weight × your entered rate per kg.
- Shuttering cost (if included) = edge contact area × your entered rate per m² (or per sq ft).
How Is the Raft Foundation Quantity Calculated?
The calculation happens in three parts — concrete volume, two-way mesh steel, and shuttering area — then an optional cost estimate on top.
Step 1 — Concrete Volume
Wet Volume = Length × Width × Thickness
Dry Volume = Wet Volume × 1.54
Cement Bags = Cement Volume ÷ 0.0347 m³/bag (50 kg bags)
Dry volume accounts for the voids between aggregate particles that disappear once the concrete is mixed and compacted. The dry volume is split into cement, sand, and aggregate using the selected mix ratio, and wastage is applied once to the final quantities.
Step 2 — Two-Way Mesh Steel
X-direction bar length = Length − (2 × Cover)
X-direction bar count = ROUND UP((Width − 2×Cover) ÷ Spacing) + 1
Y-direction bar length = Width − (2 × Cover)
Y-direction bar count = ROUND UP((Length − 2×Cover) ÷ Spacing) + 1
Unit Weight (kg/m) = Diameter² ÷ 162
Bars running along the length are spaced out and counted across the width, and vice versa — the same convention used on this site's Slab Steel calculator, applied once for the bottom mesh and again for the optional top mesh.
Step 3 — Edge Shuttering (Optional)
Perimeter = 2 × (Length + Width)
Contact Area = Perimeter × Thickness
Only the vertical edge strip around the raft's perimeter needs formwork — the underside rests on PCC/blinding and the top is finished open, the same logic used for isolated/strip footings.
Worked Example
This example walks through your current inputs above, using the same steps as the Formula section.
Enter valid inputs above to generate the worked example.
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Disclaimer: This calculator provides approximate results for planning and estimation purposes only. Actual requirements may vary based on site conditions, materials, workmanship, and local building regulations. Always consult a qualified engineer, architect, or construction professional before making final decisions.