---
title: "Density of Steel and Stainless Steel: kg/m3 and Weight"
source: "https://www.laxconsteels.com/density-of-steel/"
description: "Steel has a density of 7,850 kg/m3; austenitic stainless 7,930 to 8,000 kg/m3. Values by grade family, unit conversions and weight per metre formulas for bar."
---
# Density of Steel and Stainless Steel: kg/m3, g/cm3 and the Weight per Metre of Bar

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Published 11 September 2026 8 min read

The density of steel is 7,850 kilograms per cubic metre (7.85 g/cm3), the value that Indian and European structural standards fix for carbon steel and that every weight chart for mild steel bar is computed from. Stainless steel is denser than carbon steel or lighter than it depending on the family: the austenitic grades such as [304](https://www.laxconsteels.com/grades/aisi-304/) and [316](https://www.laxconsteels.com/grades/aisi-316/) are 7,930 to 8,000 kg/m3, the ferritic and martensitic chromium grades are 7,700 to 7,750 kg/m3, and the duplex grades sit between the two at about 7,800 kg/m3. The difference across the whole range is under four percent, which is why a single figure of 7,850 serves for structural calculation, and why it does not serve for estimating the mass of a stainless consignment. The density of a grade, multiplied by the cross-section of the bar, gives its weight per metre.

## Density of steel by grade family

Steel is an alloy of iron, and pure iron has a density of 7,874 kg/m3 at room temperature. Carbon, which is light, and the small quantities of manganese and silicon in a plain carbon steel move the figure to 7,850 kg/m3, the value stated in IS 2062, IS 1786, EN 1991-1-1 and EN 10025 for the purpose of computing mass. Alloying with heavier elements raises the density and alloying with lighter ones lowers it. Nickel (8,908 kg/m3) and molybdenum (10,280 kg/m3) are both denser than iron, so the austenitic grades that carry 8 to 14 percent nickel, and 316 with its 2 to 3 percent molybdenum on top, are the densest common steels. Chromium (7,190 kg/m3) is lighter than iron, so a ferritic grade such as [430](https://www.laxconsteels.com/grades/aisi-430/), which is 16 to 18 percent chromium and no nickel, is lighter than carbon steel.

*Density of steel and stainless steel by family and grade*

| Family | Grades | Density, kg/m3 | g/cm3 | lb/in3 |
| --- | --- | --- | --- | --- |
| Pure iron | Fe | 7,874 | 7.87 | 0.284 |
| Carbon and mild steel | IS 2062 E250, S355, C45, EN8 | 7,850 | 7.85 | 0.284 |
| Low alloy steel | EN19, EN24, 4140, 4340, 8620 | 7,850 | 7.85 | 0.284 |
| Austenitic stainless | 304, 304L, 321, 310S | 7,900 to 7,930 | 7.90 to 7.93 | 0.286 |
| Austenitic stainless with molybdenum | 316, 316L, 316Ti | 7,980 to 8,000 | 7.98 to 8.00 | 0.289 |
| Ferritic stainless | 430, 409 | 7,700 to 7,750 | 7.70 to 7.75 | 0.278 |
| Martensitic stainless | 410, 420, 431 | 7,700 to 7,750 | 7.70 to 7.75 | 0.278 |
| Duplex stainless | 2205, 2507 | 7,800 | 7.80 | 0.282 |
| Precipitation hardening | 17-4 PH, 15-5 PH | 7,780 to 7,800 | 7.78 to 7.80 | 0.281 |

The stainless figures are those of EN 10088-1, which lists density per grade to two decimal places in kg/dm3, and of the ASM handbook values that ASTM specifications refer to. A given grade is quoted at 7,930 in one source and 8,000 in another because the composition window of the grade is wide enough to move the density by that much, and because the handbooks round differently. For a weight calculation the mill's own figure for its grade governs, and on a certificate the stated mass is what was weighed, not what was computed.

## Units and conversions

The SI unit is kilograms per cubic metre. The same number expressed in grams per cubic centimetre, kilograms per cubic decimetre or tonnes per cubic metre is divided by one thousand: 7,850 kg/m3 is 7.85 g/cm3, 7.85 kg/dm3 and 7.85 t/m3. In imperial units carbon steel is 0.2836 pounds per cubic inch or 490 pounds per cubic foot; the austenitic stainless grades are 0.286 to 0.289 lb/in3 (494 to 499 lb/ft3). Specific gravity, the ratio of the density to that of water, is the same number as the density in g/cm3 and has no unit.

Density falls slightly with temperature because the metal expands. Austenitic stainless steel expands at about 17 micrometres per metre per kelvin between 0 and 100 degrees Celsius, roughly one and a half times the rate of carbon steel, so its density at 500 degrees Celsius is about two percent below the room temperature value. For weight calculation the room temperature figure is the only one used.

## Weight per metre of bar from the density

The mass of a bar is its density multiplied by its volume, and the volume of a prismatic bar is its cross-sectional area multiplied by its length. With the section dimension in millimetres and the density in kg/m3, the weight in kilograms per metre is the area in square millimetres multiplied by the density and divided by one million. For a round bar of diameter d the area is 0.7854 d2, which at 7,850 kg/m3 gives the factor 0.006165 and the familiar rule that a steel round bar weighs d2 divided by 162 kilograms per metre; at 7,930 kg/m3 the factor is 0.006228 and the divisor is 160.6.

*Weight per metre formulas for bar sections at two densities*

| Section | Dimension | Area, mm2 | kg/m at 7,850 (carbon steel) | kg/m at 7,930 (304) |
| --- | --- | --- | --- | --- |
| Round | diameter d | 0.7854 d2 | 0.006165 d2 | 0.006228 d2 |
| Square | side s | s2 | 0.007850 s2 | 0.007930 s2 |
| Hexagon | across flats s | 0.8660 s2 | 0.006798 s2 | 0.006867 s2 |
| Flat | width w, thickness t | w t | 0.007850 w t | 0.007930 w t |
| Round tube | outside diameter D, wall t | 3.1416 t (D minus t) | 0.02466 t (D minus t) | 0.02491 t (D minus t) |

Worked example: a 50 mm round bar in grade 304. The area is 0.7854 multiplied by 2,500, which is 1,963.5 mm2. At 7,930 kg/m3 the bar weighs 15.57 kg per metre, and a 6 metre length weighs 93.4 kg. Computed at the carbon steel figure of 7,850 it would be 15.41 kg per metre, a difference of one percent, so a theoretical mass worked out for a twenty tonne consignment at the wrong density sits about two hundred kilograms away from what the weighbridge reads. A 32 mm across-flats hexagon in 304 is 0.006867 multiplied by 1,024, or 7.03 kg per metre; a 50 by 10 mm flat in 304 is 0.00793 multiplied by 500, or 3.97 kg per metre.

The [weight calculator](https://www.laxconsteels.com/weight-calculator/) performs this arithmetic for every section and grade the site lists, and the [weight charts](https://www.laxconsteels.com/weight-charts/) tabulate it for the standard sizes. The same formulas underlie every published weight table; where two tables disagree for the same size, they were computed at different densities.

## Unit weight of steel in Indian practice

The term unit weight, common in Indian civil engineering, is the density expressed as a weight per unit volume for load calculation. At standard gravity, 9.80665 metres per second squared, a density of 7,850 kg/m3 is 77.0 kN/m3. The figure met in practice is 78.5 kN/m3, which is the conventional design value IS 875 Part 1 states for the dead load of steel and the upper end of the 77.0 to 78.5 kN/m3 that EN 1991-1-1 tabulates for it; it corresponds to rounding gravity to 10 and is deliberately on the safe side. The arithmetic conversion and the code value are different numbers, and a design uses the one its code states. IS 1786 computes the mass per metre of reinforcing bar from the same density, which is where the d2/162 rule comes from, and a 12 mm rebar is 144 divided by 162, or 0.889 kg per metre. The tolerance IS 1786:2008 allows on that mass varies with the nominal size and is wider on an individual sample than on the batch mean; for a 12 mm bar an individual sample may vary by 5 percent. Structural sections under IS 808 and plates under IS 2062 are tabulated on 7,850 as well. Stainless bar under IS 6603 is not tabulated by mass in the standard, and its weight is computed from the grade's own density as above.

## Steel against other metals

Steel is a dense engineering material but far from the densest metal. Aluminium alloys are 2,700 kg/m3, about a third of steel, and titanium alloys are 4,430 to 4,510 kg/m3, about 57 percent of it; both are chosen where weight, not stiffness, governs the design. Cast iron is 7,100 to 7,300 kg/m3 because of the graphite it contains. Copper is 8,960 kg/m3, brass about 8,500, lead 11,340 and tungsten 19,250. Strength per unit of weight, rather than density alone, decides the material of a part, which is the comparison made in the [steel versus aluminium article](https://www.laxconsteels.com/steel-vs-aluminium-guide/).

## Bar sold by weight

Laxcon Steels supplies [hot rolled round bar](https://www.laxconsteels.com/products/hot-rolled-round-bars/) from 16 to 125 mm and [bright bar](https://www.laxconsteels.com/products/bright-bars/) from 5 to 115 mm in the austenitic, ferritic, martensitic, duplex and precipitation hardening grades of the table above, together with [hexagonal](https://www.laxconsteels.com/products/hexagonal-bright-bars/), square and flat bar. Bar is invoiced by the weighed mass of the consignment, and the mass per metre of a size in a given grade is stated on request against the density of that grade.

## Frequently asked questions

### What is the density of steel in kg/m3?

Carbon steel and low alloy steel have a density of 7,850 kg/m3, the value the Indian and European structural standards use for computing the mass of sections, plates and bars. The figure is 7.85 g/cm3, 0.284 lb/in3 or 490 lb/ft3 in other units.

### Is stainless steel heavier than mild steel?

The austenitic stainless grades are heavier: 304 is about 7,930 kg/m3 and 316 about 8,000, one to two percent above mild steel, because of the nickel and molybdenum they contain. The ferritic and martensitic grades, which have chromium but no nickel, are lighter than mild steel at 7,700 to 7,750 kg/m3.

### How is the weight per metre of a round bar calculated?

The cross-sectional area in square millimetres is multiplied by the density in kg/m3 and divided by one million. For a round bar that reduces to 0.006165 multiplied by the diameter squared for carbon steel, the d2/162 rule, and 0.006228 multiplied by the diameter squared for grade 304.

### Why do weight charts for the same size disagree?

They were computed at different densities. A chart built on 7,850 kg/m3 understates 304 by one percent and 316 by two percent; a chart built on 8,000 overstates a ferritic grade by three percent. The grade's own density from EN 10088-1 or the ASM tables gives the figure a mill weighs against.

## Sources

- EN 10088-1, Stainless steels, list of stainless steels: physical properties per grade, including density.
- IS 2062, Hot rolled medium and high tensile structural steel; IS 1786, High strength deformed steel bars for concrete reinforcement; IS 875 Part 1, Dead loads.
- EN 1991-1-1, Eurocode 1, Actions on structures: densities of construction materials.
- ASM Handbook, Volume 1, Properties and Selection: Irons, Steels and High-Performance Alloys: the physical property tables for wrought carbon, alloy and stainless steels.
- The grade properties in the [Laxcon grade reference](https://www.laxconsteels.com/grades/).

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