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Structural Design
Rebar Calculator
Calculate rebar areas, number of bars, spacing, beam layouts and development lengths for any bar size. Covers common metric reinforcing-bar diameters (labelled T6-T40, a widely-used convention, not a formal Eurocode designation) and US customary bar sizes (#3-#18), with SI and Imperial units.
Eurocode Bar Reference
| Bar | Diameter (mm) | Area (mm²) | Weight (kg/m) |
|---|---|---|---|
| T6 | 6 | 28.274 | 0.222 |
| T8 | 8 | 50.265 | 0.3946 |
| T10 | 10 | 78.54 | 0.6165 |
| T12 | 12 | 113.1 | 0.8878 |
| T14 | 14 | 153.94 | 1.208 |
| T16 | 16 | 201.06 | 1.578 |
| T20 | 20 | 314.16 | 2.466 |
| T25 | 25 | 490.87 | 3.853 |
| T28 | 28 | 615.75 | 4.834 |
| T32 | 32 | 804.25 | 6.313 |
| T40 | 40 | 1256.6 | 9.865 |
| T50 | 50 | 1963.5 | 15.413 |
1. Total Area from Number of Bars
Total area (As)
804.25 mm²
2. Minimum Bars for Required Area
| Bar | Bar area (mm²) | Min. bars | Provided (mm²) |
|---|---|---|---|
| T6 | 28.274 | 43 | 1215.8 |
| T8 | 50.265 | 24 | 1206.4 |
| T10 | 78.54 | 16 | 1256.6 |
| T12 | 113.1 | 11 | 1244.1 |
| T14 | 153.94 | 8 | 1231.5 |
| T16 | 201.06 | 6 | 1206.4 |
| T20 | 314.16 | 4 | 1256.6 |
| T25 | 490.87 | 3 | 1472.6 |
| T28 | 615.75 | 2 | 1231.5 |
| T32 | 804.25 | 2 | 1608.5 |
| T40 | 1256.6 | 1 | 1256.6 |
| T50 | 1963.5 | 1 | 1963.5 |
3. Area per Meter Width
As per meter width
1340.4 mm²/m
- The Beam Reinforcement tab checks single-layer minimum clear-spacing only — minimum/maximum reinforcement ratios and bundled-bar rules are not checked.
- Development-length formulas use simplifying, code-permitted conservative defaults rather than every possible refinement — your actual required length may be shorter with those effects properly included.
- ACI’s general development-length equation additionally needs clear cover and center-to-center bar spacing, since both feed its confinement term directly.
- The PASS/FAIL check on the Slab Reinforcement tab compares As,provided against As,required directly — it doesn’t check crack-width, deflection, or any other serviceability limit.
- Switching between Eurocode and ACI resets a few default values (e.g. fy, fck) on the Development Length tab to that unit system’s typical starting point — re-check these against your actual project materials.
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