How to Calculate Rebar Weight: Steel per Meter & the D²÷162 Formula (2026 Guide)
Reinforcement steel is the second-largest cost item in reinforced concrete after the concrete itself, and calculating its weight accurately determines the project budget and the steel order from the mill. An estimation error means either a shortage that halts work or a costly surplus that rusts on site. In this guide you will learn step by step: the bar weight-per-meter formula (D²÷162), the weight table for every diameter from T8 to T32, how to convert the number and length of bars into kilograms and tons, roughly how much steel a cubic meter of concrete needs, and the Saudi SBC code angle (yield stress, laps, and minimum reinforcement). Every value here matches exactly the free Steel Calculator on “Site Engineer”.
🧮 The Rebar Weight Formula
D² ÷ 162 — where D is the bar diameter in millimeters.
- Derived from steel density (7850 kg/m³): weight = section area (π/4 × D²) × 1m × 7850, which simplifies in units to D²÷162.
- Example: T12 = 12²÷162 = 144÷162 = 0.888 kg/m · T16 = 256÷162 = 1.578 kg/m.
Then: total weight = weight/m × total length, where total length = number of bars × bar length. Add a 5–7% waste allowance for offcuts and lap splices. The commercial bar length is 12m (sometimes 6m).
📋 Steps to Calculate Steel Weight
- Determine the bar diameter: Read the required reinforcement diameter (T8 to T32) from the structural drawings for each element.
- Calculate weight per meter: Apply weight/m = D²÷162, or take the ready value from the reference table below.
- Calculate total length: Multiply number of bars × single bar length for each diameter separately to get the total length in meters.
- Calculate net weight: Multiply total length × weight/m = net weight in kilograms for each diameter.
- Add waste: Increase the weight by 5 to 7% to cover offcuts and lap splices between bars.
- Sum and convert to tons: Sum the weights of all diameters and divide by 1000 to get the weight in tons for the mill order.
✅ Worked Example
50 bars of T16 at 12m length with 5% waste:
Enter the same inputs in the Steel Calculator and you'll get the exact same result — these values come from the calculator's own formula (D²÷162).
📊 Rebar Weight Table (D²÷162)
| Diameter | Area (mm²) | Weight (kg/m) | 12m bar (kg) |
|---|---|---|---|
| T8 | 50.3 | 0.395 | 4.74 |
| T10 | 78.5 | 0.617 | 7.40 |
| T12 | 113.1 | 0.888 | 10.66 |
| T14 | 153.9 | 1.208 | 14.50 |
| T16 | 201.1 | 1.578 | 18.94 |
| T18 | 254.5 | 1.998 | 23.98 |
| T20 | 314.2 | 2.466 | 29.59 |
| T25 | 490.9 | 3.853 | 46.24 |
| T32 | 804.2 | 6.313 | 75.76 |
🛡️ The Saudi Angle: SBC Code & Reinforcement
The D²÷162 weight formula is physical and does not change with the code, but design properties do change with the chosen code. The Saudi SBC 304 code (aligned with ACI 318) uses a yield stress of fy = 420 MPa for deformed bars.
Practical code points: minimum reinforcement (ρmin) prevents sudden cracking and is checked by the calculator; concrete cover is 25mm internally, rising to 40–75mm in foundations and exposed conditions to protect the steel from rust; and the lap (splice) length depends on the diameter and the concrete strength and is computed automatically by the calculator.
🚫 Common Steel Calculation Mistakes
- Confusing nominal and actual diameter: use the nominal diameter (T16 = 16mm) in the D²÷162 formula.
- Forgetting laps: lap splices alone can add 8–12% of the weight in columns and long bars — don't rely on offcut waste only.
- Wrong bar length: the commercial 12m bar is standard; confirm it before converting weight to a bar count.
- Ignoring stirrups and dowels: include them in the steel weight — stirrups are a large separate item in columns and beams.
- Mixing tons and kilograms: when ordering steel, remember 1 ton = 1000 kg to avoid a tenfold error.