Slab Reinforcement Estimator
Estimate the rebar needed for a rectangular concrete slab: number of bars in each direction, cutting lengths, total steel weight with wastage, kg per m² and a minimum-steel check, from slab size, cover, bar diameter and spacing.
Input
Slab
Bars Parallel to the Short Side
Bars Parallel to the Long Side
Added to the total weight for cutting waste and laps. 3–5 % is typical.
Output
| Property | Value |
|---|---|
| No data yet | |
More ways to use this tool
REST API
curl -X POST https://api.iotools.cloud/v1/tool/slab-reinforcement-estimator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"slabLength": "5",
"slabWidth": "4",
"thickness": "150",
"cover": "20",
"layers": "1",
"shortDia": "10",
"shortSpacing": "150",
"longDia": "8",
"longSpacing": "200",
"wastage": "5"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `slab-reinforcement-estimator` tool (Slab Reinforcement Estimator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.
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| Cost per API/MCP call | From 5 credits |
|---|---|
| Need more credits? | View pricing |
Also available with
Guides
Estimate the rebar for a rectangular concrete slab. Enter the slab size, thickness and cover, then the bar diameter and spacing in each direction, and get the number of bars, total length, steel weight with wastage, kg per m² and a minimum-steel check.
How to use it
- Enter the slab length, width, thickness and clear cover.
- Choose whether the slab has a bottom mesh only or top and bottom mesh.
- Set the bar diameter and spacing for bars running parallel to the short side and to the long side.
- Adjust wastage for cutting waste and laps.
How the quantities are worked out
- Bars parallel to the short side are spaced along the long side, and the other way around. Number of bars = ⌊(span − 2 × cover) ÷ spacing⌋ + 1.
- Each bar's cutting length is the slab dimension minus cover at both ends (hooks, bends and lap lengths are covered by the wastage allowance).
- Weight per metre = π/4 × d² × 7850 kg/m³, which is the familiar d²/162 kg/m with d in mm.
Minimum steel check
The provided steel area per metre width (π/4 × d² ÷ spacing) is compared with 0.12 % of the gross section (thickness × 1000 mm), the usual minimum for high-strength deformed bars in IS 456 and in the same range as ACI 318 shrinkage steel.
Notes
This is a quantity estimate, not a structural design. Slab thickness, bar size and spacing must come from a structural calculation, and extra bars at supports, openings and bent-up bars are not included.