Weight of a solid round steel bar from its diameter, length and density, with weight per metre and per foot.
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A steel bar's weight is its volume times the density of the steel. For a solid round bar the volume is the cross-section π d² ÷ 4 times the length, so the weight grows with the square of the diameter: double the diameter and the bar is four times as heavy. Enter the diameter, the length and the steel grade, in millimetres and metres or inches and feet; the calculator returns the total weight in kilograms and pounds, the weight per metre and per foot, and the volume. The guide below gives the one-line shortcut for carbon steel, a weight table for common metric bars and US rebar sizes, the density of different steels, and how to handle square, flat and hexagonal bars.
Select SI (mm, m, kg) or Imperial (in, ft, lb).
Enter the bar diameter — for rebar, the nominal diameter of the bar number (#4 = 0.5 in).
Enter the bar length.
Select the steel type — carbon and low-alloy steel at 7,850 kg/m³ is the default.
Press Calculate. For an order, add an allowance for saw cuts and end trimming — ask the supplier how they cut.
By O.E. — Partner, chairman of the board and CEO of a metal products manufacturer for 21 years; the company exports to 45 countries.
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Weight = (π × d² ÷ 4) × L × ρ. For carbon steel at 7,850 kg/m³ with d in millimetres the formula reduces to kg per metre = d² × 0.006165 (because 7,850 × π ÷ 4 × 10⁻⁶ = 0.006165); in US units, lb per foot = d² × 2.673 with d in inches. A 20 mm bar: 400 × 0.006165 = 2.466 kg/m, so a 6 m length weighs 14.80 kg.
| Symbol | Meaning |
|---|---|
| d | Bar diameter (mm or in) |
| L | Length (m or ft) |
| ρ | Steel density, kg/m³ (7,850 for carbon and low-alloy steel) |
120 mm carbon steel, 6 m.
20² × 0.006165 × 6
14.797 kg · 2.4662 kg/m
A typical stock length.
212 mm, 12 m.
0.8878 kg/m × 12
10.654 kg
350 mm stainless 304 (7,900 kg/m³), 3 m.
π × 0.025² × 3 × 7,900
46.535 kg · 15.5116 kg/m
About 0.6% heavier than carbon steel of the same size.
41 in carbon steel, 20 ft.
1² × 2.673 × 20
53.457 lb · 2.6729 lb/ft
| Diameter | kg/m | Diameter | kg/m |
|---|---|---|---|
| 8 mm | 0.395 | 20 mm | 2.466 |
| 10 mm | 0.617 | 25 mm | 3.853 |
| 12 mm | 0.888 | 32 mm | 6.313 |
| 16 mm | 1.578 |
Carbon steel, 7,850 kg/m³.
Rebar is sold by bar number — the nominal diameter in eighths of an inch. Its nominal weight is that of a plain round bar of the nominal diameter, so the calculator reproduces the standard figures:
| Bar | Nominal diameter | Calculator (lb/ft) | ASTM A615 table (lb/ft) |
|---|---|---|---|
| #3 | 0.375 in | 0.376 | 0.376 |
| #4 | 0.500 in | 0.668 | 0.668 |
| #5 | 0.625 in | 1.044 | 1.043 |
| #6 | 0.750 in | 1.504 | 1.502 |
| #7 | 0.875 in | 2.046 | 2.044 |
| #8 | 1.000 in | 2.673 | 2.670 |
| #9 | 1.128 in | 3.401 | 3.400 |
| #10 | 1.270 in | 4.311 | 4.303 |
| #11 | 1.410 in | 5.314 | 5.313 |
For a bundle, multiply lb/ft by length and count: twenty #5 bars 20 ft long weigh 20 × 20 × 1.043 ≈ 417 lb. The full chart is on the Rebar Size Chart page.
Carbon and low-alloy steels — A36, S275, S355, 1045, 4140, 4340 and rebar — are all designed with 7,850 kg/m³. Austenitic stainless steels are 1–2% heavier: 7,900 kg/m³ for 304 and 8,000 kg/m³ for 316. Ferritic 430 is about 7,750 kg/m³. Tool steels are not heavier by default: Uddeholm's data sheets give 7,800 kg/m³ for the hot-work steel H13 (Orvar Supreme) and 7,700 kg/m³ for the cold-work steel D2 (Sverker 21), whose high chromium and carbon content make it slightly lighter than mild steel.
For an order or a lifting plan the actual bar size matters more than the grade: hot-rolled bars have a diameter tolerance, so weigh a sample or ask for the mill's theoretical weight if precision matters, and add an allowance for saw cuts and end trimming.
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