TryBuildCalcGrade Beam Steel CalculatorGrade beam reinforcement estimator
Calculate concrete, steel, and shuttering quantity for a grade (plinth) beam tying the foundation together.
🕒 Last updated: August 12, 2026
Grade Beam Dimensions
ℹ️Sum of every grade beam run in the building — around the perimeter and any internal ties — not a single span.
ℹ️Commonly matches the wall thickness above it.
Concrete
Reinforcement
ℹ️Commonly 150-200 mm centre-to-centre for a plinth beam.
Lap Splices
ℹ️Commonly 40-50× diameter depending on the applicable code and concrete grade — a grade beam's total run almost always exceeds one 12m stock length.
Shuttering
Cost
For 60.0 m (196.9 ft) of grade beam at 230 × 300 mm, you need approximately 4.35 m³ of concrete and 450.0 kg of reinforcement steel.
Concrete
Concrete volume: 4.35 m³ (153.5 cft)
Cement: 35.1 bags
Sand: 1.83 m³ (64.5 cft)
Aggregate: 3.65 m³ (129.0 cft)
Steel Reinforcement
Top Bars: 2 × 12 mm
Bottom Bars: 2 × 16 mm
Stirrups: 401 × 8 mm
Total steel weight: 450.0 kg
Side Shuttering
Contact area: 36.00 m² (387.5 sqft)
| Bar Type | Diameter | Count / Spacing | Cutting Length | Total Length | Weight |
|---|---|---|---|---|---|
| Top Bars | 12 mm | 2 | 61.840 m | 123.68 m | 109.94 kg |
| Bottom Bars | 16 mm | 2 | 62.480 m | 124.96 m | 197.47 kg |
| Stirrups | 8 mm | 150 mm c/c (401) | 0.900 m | 360.90 m | 142.58 kg |
Assumptions Used
Steel weight: d² ÷ 162 (kg/m) | Stirrup hook allowance: 10 × diameter per end | Concrete dry volume factor: 1.54 | Shuttering (if included) is side-only, since the beam bears on PCC/ground below
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete Grade Beam Calculator.
Grade beam reinforcement schedule with lap splices
This page is set up for grade beam reinforcement — top bars, bottom bars, and stirrups — with lap splices turned on by default, since a grade beam's total run almost always exceeds a standard 12 m stock bar length.
Edit diameter, count, or spacing and the bar schedule, total weight, and worked example update from the active values — concrete and shuttering are still calculated in the same result.
- Splices per bar = ROUND UP(effective length ÷ 12 m) − 1, added automatically once the run exceeds one stock length.
- Stirrup count = ROUND UP(total length ÷ spacing) + 1; cutting length includes a hook allowance of 10 × diameter at each end.
- Top and bottom bars can use different diameters and counts, matching real structural drawings.
How Is the Grade Beam Quantity Calculated?
The calculation happens in three parts — concrete volume, steel reinforcement (with optional lap splices), and shuttering area — then an optional cost estimate on top.
Step 1 — Concrete Volume
Wet Volume = Total Length × Width × Depth
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 — Steel Reinforcement
Effective Length = Total Length − (2 × Concrete Cover)
Splices per Bar (if laps included) = ROUND UP(Effective Length ÷ 12 m) − 1
Cutting Length per Bar = Effective Length + (Splices × Lap Multiplier × Diameter)
Stirrups = ROUND UP(Total Length ÷ Spacing) + 1
Unit Weight (kg/m) = Diameter² ÷ 162
Top and bottom bars run the full length minus end cover; when lap splices are enabled, this calculator estimates how many 12m stock-length splices each bar needs and adds the extra material each splice requires. Stirrups are closed loops sized to the concrete section minus cover, with a hook allowance added at both ends.
Step 3 — Shuttering Area (Optional)
Side Area = 2 × Depth × Total Length
Only the two vertical side faces need formwork — a grade beam typically bears on PCC/blinding at the bottom, the same reasoning used for footing and raft edge shuttering on this site.
Worked Example
This example walks through your current inputs above, using the same steps as the Formula section.
Input Values Used
| Input | Value | Why it is used |
|---|---|---|
| Total plinth beam run length | 60 m | Sets concrete volume and every bar's base length |
| Beam width × depth | 230mm × 300mm | Sets the concrete cross-section and the shuttering side area |
| Mix ratio / wastage | 1:1.5:3, 5% wastage | Converts wet volume to cement bags and adds a buffer for site losses |
| Cover / bar diameters / stirrups | 40 mm cover, 12 mm top × 2, 16 mm bottom × 2, 8 mm @ 150 mm | Sets bar cutting length and stirrup count/size |
| Lap multiplier | 40× diameter | Adds splice length for every 12m stock length exceeded |
Step 1 — Concrete
| Calculation | Substitution | Result |
|---|---|---|
| Wet volume | 60.00 × 230mm × 300mm | 4.140 m³ |
| With 5% wastage | 4.140 × 1.05 | 4.347 m³ (35.1 bags) |
Step 2 — Steel
| Bar Type | Substitution | Weight |
|---|---|---|
| Top Bars | 2 × 61.840 m × 12²÷162 | 109.94 kg |
| Bottom Bars | 2 × 62.480 m × 16²÷162 | 197.47 kg |
| Stirrups | 401 × 0.900 m × 8²÷162 | 142.58 kg |
| Total steel | Sum of all rows | 449.98 kg |
Therefore, 60.0 m of grade beam needs approximately 4.35 m³ of concrete and 450.0 kg of steel, plus 36.0 m² of side shuttering.
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.