How to Calculate Rebar Weight: Steel per Meter & the D²÷162 Formula (2026 Guide)
This guide estimates rebar weight from diameter, length and count. The actual order depends on approved schedules, cutting and splice details; the calculator's yield, cover and minimum-steel presets do not prove code compliance.
🧮 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.
- D²÷162 approximates T12≈0.889 and T16≈1.580 kg/m; the calculator lookup uses T12=0.888 and T16=1.578 kg/m for outputs.
Then: total weight = weight/m × total length, where total length = count × bar length. The example selects 5% waste from calculator options; determine cuts and laps from approved schedules. Its 12m bar is an input, not a specification for every supplier.
📋 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.
- Set a cutting allowance: Choose a calculator estimating allowance, then verify cut and splice lengths in approved schedules.
- 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
D²÷162 approximates weight from steel density; it is not a reinforcement design rule. ASTM A615 covers multiple bar grades, so selecting SBC in the calculator does not make every deformed bar fy=420MPa.
Use approved bar schedules for ordering and verify the actual steel grade certificate before adopting any yield value.
🚫 Common Steel Calculation Mistakes
- Confusing nominal and actual diameter: use the nominal diameter (T16 = 16mm) in the D²÷162 formula.
- Forgetting laps: include splice lengths from approved reinforcement drawings; preset waste does not capture every project detail.
- 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.
📚 Sources and Citation Scope
This page explains the calculator logic and discloses its assumptions. Each link supports only the scope stated beside it; it does not mean the source organization reviewed or approved the calculator. The site does not claim a named engineering review for this page.
- ASTM A615/A615M — Reinforcing BarsScope of reinforcing bars, sizes, and yield grades; element-level quantity rates remain planning assumptions.
- ACI 318 — Structural Concrete Code PortalA reinforced-concrete design and detailing reference, not a source for a fixed steel-per-cubic-metre allowance.