25 mm Reinforcing Bar - EN / Eurocode
25 mm is a EN / Eurocode reinforcing bar to EN 10080 / EN 1992-1-1. Its nominal diameter is 25 mm, giving a cross-section area As of 490.9 mm² and a mass of 3.853 kg/m. It is supplied in grade B500A / B500B / B500C with characteristic yield f_yk = 500 MPa. The tables below give the total steel area for 1-10 bars and the area per metre of width at common bar spacings.
| d | Nominal diameter | 25 mm |
| As | Cross-section area | 490.9 mm² |
| m | Mass per metre | 3.853 kg/m |
| u | Nominal perimeter | 78.5 mm |
| f_yk | Characteristic yield | 500 MPa |
| Bars | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| As (mm²) | 491 | 982 | 1,473 | 1,964 | 2,455 | 2,945 | 3,436 | 3,927 | 4,418 | 4,909 |
| s (mm) | 75 | 100 | 125 | 150 | 175 | 200 | 250 | 300 |
|---|---|---|---|---|---|---|---|---|
| As/m (mm²/m) | 6,545 | 4,909 | 3,927 | 3,273 | 2,805 | 2,455 | 1,964 | 1,636 |
Source: EN 10080 / EN 1992-1-1. Area = π/4 × d² for metric bars; ASTM areas are the standard's tabulated nominal values. Grades available: B500A, B500B, B500C.
Understanding these values
25 mm is a ribbed reinforcing bar to EN 10080 / EN 1992-1-1, the Eurocode reinforcement standard. It is produced in B500A / B500B / B500C, where the 500 is the characteristic yield f_yk in MPa and the trailing letter is the ductility class rather than a strength difference. Its nominal diameter is 25 mm, which gives a cross-sectional area As of 490.9 mm² from pi/4 times the diameter squared, and a mass of 3.853 kg/m - so a 12 m length weighs about 46.2 kg. The nominal perimeter, used in bond and anchorage calculations, is 78.5 mm.
It is supplied in B500A, B500B, B500C, all sharing f_yk = 500 MPa and differing in ductility class: the trailing A, B or C sets the elongation and hardening requirements, with C required where plastic rotation capacity matters. The grade affects the strength you design to, not the geometry: the area of 490.9 mm² and the mass of 3.853 kg/m are the same whichever grade of EN / Eurocode bar is specified.
For slabs and walls the number you need is area per metre width, which is the bar area times 1,000 divided by the spacing. At 150 mm centres 25 mm gives 3273 mm²/m, at 200 mm centres 2455 mm²/m, and at 250 mm centres 1964 mm²/m. Compare those against the As,req from your slab design, take the first arrangement that satisfies it, and then check the spacing against the maximum bar spacing EN 1992-1-1 allows for crack control - a larger bar at wider centres can meet the area and still fail that limit.
If you are working across standards, the nearest equivalents by area are TCVN (Vietnam) 25 mm at 490.9 mm² (effectively identical), ASTM (US) #8 (No. 8) at 510 mm² (4% larger), BS (UK) H25 (25 mm) at 490.9 mm² (effectively identical). Matching on area is the right first step, but it is not a code-sanctioned substitution: changing standard means re-checking anchorage length, lap length, bond and crack width, because those depend on bar surface geometry and the concrete, not on area alone.