Steel Rod Weight Calculator - Diameter, Length & Material
Steel rod weight calculator: enter diameter, length, quantity, and material to get weight per meter, per rod, and total weight, in metric or imperial units.
Steel Rod Weight Calculator
Input Parameters
Results
Formula
m = ρ × (π / 4) × d² × L
Densities: carbon steel 7850 kg/m³ (0.2836 lb/in³); stainless steel 304 8000 kg/m³ (0.2890 lb/in³). This matches the industry rule of thumb for steel: kg/m ≈ d² / 162.2, with d in mm.
Visualization
Documentation
What is a steel rod weight calculator?
A steel rod weight calculator finds the weight of a solid round steel bar from its diameter, length, and the number of rods. It works out the weight per unit length, the weight of one rod, and the total weight for the whole batch. It also reports the density used, so the result can be checked by hand.
The calculator on this page supports two materials, carbon (mild) steel and stainless steel 304, and both metric units (millimetres and metres) and imperial units (inches and feet).
How to calculate steel rod weight
A steel rod is a cylinder, so its weight comes from ordinary cylinder geometry. Multiply the cross-sectional area of the rod by its length to get the volume, then multiply the volume by the density of steel to get the mass.
Steel rod weight formula
- m — mass of one rod (kilograms in metric, pounds in imperial)
- ρ (rho) — density of the steel (kilograms per cubic metre, or pounds per cubic inch)
- d — diameter of the rod (metres in metric, inches in imperial)
- L — length of the rod (metres in metric, feet in imperial)
- π/4 × d² — cross-sectional area of the round rod
To find the weight of several identical rods, multiply the weight of one rod by the quantity.
Steel densities used
- Carbon steel (mild steel): 7850 kg/m³ (0.2836 lb/in³). The Iowa Department of Transportation computes structural steel weight with a density of 490 lb/ft³ (7850 kg/m³). One pound per cubic inch equals 27,679.90 kg/m³, so 7850 kg/m³ is 0.2836 lb/in³.
- Stainless steel 304: 8000 kg/m³ (0.2890 lb/in³), about 1.9% denser than carbon steel.
A common shortcut used on building sites estimates the weight of carbon steel rebar as diameter squared divided by about 162, with the diameter in millimetres, giving kilograms per metre. This shortcut comes directly from the density formula above and gives the same answer to within rounding.
Worked example
Take a carbon steel rod, 12 mm in diameter and 6 metres long, with only one rod ordered.
- Convert the diameter to metres: 12 mm = 0.012 m.
- Find the cross-sectional area: (π/4) × 0.012² = 0.0001131 m².
- Multiply by the density: 0.0001131 × 7850 = 0.8878 kg per metre of length.
- Multiply by the length: 0.8878 × 6 = 5.327 kg for one rod.
- Multiply by the quantity (1): the total weight is also 5.327 kg.
So a single 12 mm x 6 m carbon steel rod weighs about 5.33 kg.
For a batch order, the quantity field scales this up. Ten rods of 20 mm diameter and 6 metres length, in carbon steel, weigh 2.4662 kg/m each, 14.797 kg per rod, and 147.97 kg in total.
Imperial example
A carbon steel rod 0.5 inches in diameter and 20 feet long weighs about 0.668 lb per foot, so one rod weighs about 13.36 lb. The calculation is the same physics as the metric case; only the input and output units change. The 0.668 lb/ft figure matches the nominal weight that the California Department of Transportation lists for a #4 reinforcing bar, nominal diameter 0.500 in.
Steel rod weight chart
Weight per metre for common round bar diameters, calculated with the formula above.
| Diameter (mm) | Carbon steel, 7850 kg/m³ (kg/m) | Stainless 304, 8000 kg/m³ (kg/m) |
|---|---|---|
| 6 | 0.222 | 0.226 |
| 8 | 0.395 | 0.402 |
| 10 | 0.617 | 0.628 |
| 12 | 0.888 | 0.905 |
| 14 | 1.208 | 1.232 |
| 16 | 1.578 | 1.608 |
| 20 | 2.466 | 2.513 |
| 25 | 3.853 | 3.927 |
| 32 | 6.313 | 6.434 |
| 40 | 9.865 | 10.053 |
| 50 | 15.413 | 15.708 |
These figures assume a plain round bar with no ribs. Ribbed (deformed) rebar is sold by nominal diameter, and its published nominal weight matches a plain bar of that diameter. The ribs make the bar wider than its nominal size: a #4 bar is 0.500 in nominal but 0.56 in across the ribs. Measuring over the ribs would overstate the weight.
Why these numbers matter
Builders and fabricators use rod weight to order the right amount of material, to price a job by weight, and to check that a delivery matches what was invoiced. Structural engineers use the self-weight of reinforcement bars as part of the load carried by a beam, column, or slab. Because steel is usually priced and shipped by weight rather than by length, an accurate weight figure affects both cost and logistics.
Frequently asked questions
How much does a 16 mm steel rod weigh per metre?
A 16 mm carbon steel rod weighs about 1.578 kg per metre. A 6-metre length of it weighs about 9.47 kg.
What is the density of steel used in this calculator?
Carbon (mild) steel is calculated at 7850 kg/m³. Stainless steel 304 is calculated at 8000 kg/m³. Both are standard handbook values.
Does the calculator work with imperial units?
Yes. Switching to imperial changes the diameter input to inches, the length input to feet, and the results to pounds per foot, pounds per rod, and pounds in total. The underlying physics does not change; only the units do.
How do I get the total weight for more than one rod?
Enter the number of rods in the quantity field. The calculator multiplies the weight of a single rod by that quantity to give the total weight.
Is this calculator accurate for rebar?
It gives the theoretical weight of a smooth round bar of a given diameter and density, which is very close to the nominal weight published for carbon steel rebar. Enter the nominal bar diameter, not the diameter measured over the ribs. Actual delivered weight can vary slightly because of manufacturing tolerances and, for ribbed rebar, the exact rib profile.
How much heavier is stainless steel 304 than carbon steel of the same size?
About 1.9% heavier, because stainless 304 has a density of 8000 kg/m³ against 7850 kg/m³ for carbon steel. A rod's weight scales directly with density, so multiplying a carbon steel result by 8000/7850 gives the stainless steel weight for the same diameter and length.
References
- Iowa Department of Transportation. Materials IM 569: Computing Structural Steel Weight (Mass). Computing Structural Steel Weight (Mass) — steel density of 490 lb/ft³ (7850 kg/m³) for weight calculations.
- National Institute of Standards and Technology. NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically. NIST SP 811, Appendix B.8 — 1 lb/in³ = 27,679.90 kg/m³.
- California Department of Transportation. Bridge Design Details, Chapter 13: Reinforcement. Table 13.1.1 ASTM Standard Reinforcing Bar Data — #4 bar: nominal diameter 0.500 in, deformation diameter 0.56 in, weight 0.668 lb/ft.