The density of stainless steel is not a single number. It is a family of numbers, organised by microstructure, and if you use the wrong one, your weight estimates, lifting calculations, and freight classifications will be off by as much as 4%.
I’ve been laser-cutting and processing stainless steel since 2007, across every grade family: austenitic 304 and 316 for food-grade enclosures, ferritic 430 for decorative trim, 2205 duplex for marine equipment, and 17-4 PH for aerospace brackets. Every one of those materials has its own density entry in our quoting system — not because the differences are large, but because they are real, they accumulate across a large assembly, and the number is too easy to get right to justify using an approximation.
This article is the complete reference. One article, all grade families, all unit systems, with the reasons behind every number.
Stainless Steel Density: The Complete Grade Table
This is the reference most articles fail to provide in full. Every major stainless grade family, with the values you need in three unit systems.
Austenitic stainless steel (200 and 300 series)
Austenitic grades are the most widely used stainless family — 304 and 316 alone cover the majority of flat-rolled stainless processed globally. They have a face-centred cubic (FCC) crystal structure at room temperature.
| Grade | UNS | Cr (%) | Ni (%) | Density (kg/m³) | g/cm³ | lb/in³ |
|---|---|---|---|---|---|---|
| 201 | S20100 | 16–18 | 3.5–5.5 | 7,880 | 7.88 | 0.285 |
| 301 | S30100 | 16–18 | 6–8 | 7,880 | 7.88 | 0.285 |
| 304 / 304L | S30400 / S30403 | 18–20 | 8–12 | 7,930 | 7.93 | 0.286 |
| 304H | S30409 | 18–20 | 8–10.5 | 7,930 | 7.93 | 0.286 |
| 309S | S30908 | 22–24 | 12–15 | 7,980 | 7.98 | 0.288 |
| 310S | S31008 | 24–26 | 19–22 | 7,980 | 7.98 | 0.288 |
| 316 / 316L | S31600 / S31603 | 16–18 | 10–14 | 7,980 | 7.98 | 0.288 |
| 317 / 317L | S31700 / S31703 | 18–20 | 11–15 | 7,980 | 7.98 | 0.288 |
| 321 | S32100 | 17–19 | 9–12 | 7,920 | 7.92 | 0.286 |
| 347 | S34700 | 17–19 | 9–13 | 7,920 | 7.92 | 0.286 |
| 904L | N08904 | 19–23 | 23–28 | 7,980 | 7.98 | 0.288 |
| 254 SMO | S31254 | 19.5–20.5 | 17.5–18.5 | 8,000 | 8.00 | 0.289 |
| AL-6XN | N08367 | 20–22 | 23.5–25.5 | 8,060 | 8.06 | 0.291 |
Ferritic stainless steel (400 series)
Ferritic grades contain chromium but no significant nickel. They have a body-centred cubic (BCC) crystal structure — the same as plain carbon steel. The absence of nickel and the BCC structure both pull density below the austenitic range.
| Grade | UNS | Cr (%) | Ni (%) | Density (kg/m³) | g/cm³ | lb/in³ |
|---|---|---|---|---|---|---|
| 409 | S40900 | 10.5–11.75 | ≤0.5 | 7,690 | 7.69 | 0.278 |
| 430 | S43000 | 16–18 | ≤0.75 | 7,720 | 7.72 | 0.279 |
| 439 | S43035 | 17–19 | ≤0.5 | 7,720 | 7.72 | 0.279 |
| 434 | S43400 | 16–18 | ≤0.75 | 7,720 | 7.72 | 0.279 |
| 444 | S44400 | 17.5–19.5 | ≤1.0 | 7,750 | 7.75 | 0.280 |
| 446 | S44600 | 23–27 | ≤0.75 | 7,650 | 7.65 | 0.276 |
Martensitic stainless steel (400 series)
Martensitic grades combine chromium with elevated carbon for hardness. They are heat-treatable and produce a body-centred tetragonal (BCT) lattice in the hardened condition — a distorted BCC. Density sits slightly above ferritic grades because of the carbon-induced lattice distortion.
| Grade | UNS | Cr (%) | C (%) | Density (kg/m³) | g/cm³ | lb/in³ |
|---|---|---|---|---|---|---|
| 410 | S41000 | 11.5–13.5 | ≤0.15 | 7,730 | 7.73 | 0.279 |
| 420 | S42000 | 12–14 | 0.15–0.40 | 7,730 | 7.73 | 0.279 |
| 440A | S44002 | 16–18 | 0.60–0.75 | 7,700 | 7.70 | 0.278 |
| 440B | S44003 | 16–18 | 0.75–0.95 | 7,700 | 7.70 | 0.278 |
| 440C | S44004 | 16–18 | 0.95–1.20 | 7,700 | 7.70 | 0.278 |
Duplex stainless steel
Duplex grades are engineered to contain approximately equal proportions of austenite and ferrite at room temperature. The density reflects this balance: it sits between the ferritic and austenitic values, consistent with the physical mixture of the two phases.
| Grade | UNS | Cr (%) | Ni (%) | Mo (%) | Density (kg/m³) | g/cm³ | lb/in³ |
|---|---|---|---|---|---|---|---|
| LDX 2101 | S32101 | 21–22 | 1.35–1.7 | 0.1–0.8 | 7,800 | 7.80 | 0.282 |
| 2304 | S32304 | 21.5–24.5 | 3–5.5 | 0.05–0.6 | 7,800 | 7.80 | 0.282 |
| 2205 | S32205 | 22–23 | 4.5–6.5 | 3.0–3.5 | 7,805 | 7.81 | 0.282 |
| 2507 (super-duplex) | S32750 | 24–26 | 6–8 | 3–5 | 7,820 | 7.82 | 0.282 |
| Zeron 100 | S32760 | 24–26 | 6–8 | 3–4 | 7,820 | 7.82 | 0.282 |
Precipitation-hardening (PH) stainless steel
PH grades achieve very high yield strength through a controlled ageing heat treatment that precipitates fine intermetallic particles in the matrix. The precipitation does not change density — only mechanical properties. All PH grades have BCC or martensitic matrix structures at room temperature after ageing, giving them densities close to the ferritic/martensitic range.
| Grade | UNS | Cr (%) | Ni (%) | Density (kg/m³) | g/cm³ | lb/in³ |
|---|---|---|---|---|---|---|
| 17-4 PH | S17400 | 15–17.5 | 3–5 | 7,780 | 7.78 | 0.281 |
| 15-5 PH | S15500 | 14–15.5 | 3.5–5.5 | 7,780 | 7.78 | 0.281 |
| 17-7 PH | S17700 | 16–18 | 6.5–7.75 | 7,810 | 7.81 | 0.282 |
| PH 13-8 Mo | S13800 | 12.25–13.25 | 7.5–8.5 | 7,760 | 7.76 | 0.280 |
For data source, please refer to the Metal Density Chart.
Stainless Steel Density in All Common Units
For the four most commonly specified grades:
| Grade | kg/m³ | g/cm³ | lb/in³ | lb/ft³ |
|---|---|---|---|---|
| 304 / 304L (austenitic) | 7,930 | 7.93 | 0.2863 | 495.0 |
| 316 / 316L (austenitic) | 7,980 | 7.98 | 0.2881 | 498.1 |
| 430 (ferritic) | 7,720 | 7.72 | 0.2788 | 481.9 |
| 2205 duplex | 7,805 | 7.81 | 0.2819 | 487.2 |
Weight formula — SI: Weight (kg) = Length (m) × Width (m) × Thickness (m) × density (kg/m³)
Worked example — 1,220 × 2,440 mm sheet, 3 mm thick, in 304: Weight = 1.220 × 2.440 × 0.003 × 7,930 = 70.9 kg
Same sheet in 430 ferritic: 1.220 × 2.440 × 0.003 × 7,720 = 69.0 kg — 1.9 kg lighter.
Same sheet in 316: 1.220 × 2.440 × 0.003 × 7,980 = 71.4 kg — 0.5 kg heavier than 304.
Over a full job lot of 50 sheets, the difference between 304 and 316 is approximately 25 kg — a meaningful difference for freight classification but negligible for structural calculations.
Why Each Stainless Family Has Its Own Density — The Crystal Structure Explanation
The density of stainless steel is not an arbitrary number attached to a grade designation. It emerges directly from the atomic-scale structure of the alloy. Understanding this eliminates guesswork when you encounter an unfamiliar stainless grade.
Austenitic grades: FCC + nickel = highest density
Austenitic stainless steels have a face-centred cubic (FCC) crystal structure. FCC packs atoms more efficiently than BCC — approximately 74% of space is occupied by atoms versus 68% for BCC. The more tightly packed structure means more mass per unit volume.
Nickel (density 8,908 kg/m³) is the key alloying element that stabilises the FCC structure at room temperature and raises bulk density above pure iron (7,874 kg/m³). The standard 304 composition carries 8–11% nickel; 316 carries 10–14%. The high-alloy austenitics — 904L, 254 SMO, AL-6XN — carry 17–28% nickel and push density to 7,980–8,060 kg/m³.
Chromium (7,190 kg/m³) is lighter than iron and partially offsets the nickel contribution. At 18–20% chromium (304), the net effect of Cr and Ni together is a density slightly above pure iron. This is why austenitic stainless falls in the 7,880–8,060 kg/m³ range.
The 200-series substitution effect. Type 201 and related grades substitute manganese (7,210 kg/m³) for much of the nickel to reduce cost. Manganese is slightly lighter than nickel (8,908 kg/m³), which is why 201 stainless (7,880 kg/m³) sits below 304 (7,930 kg/m³). The lower nickel content also shifts the density downward.
Ferritic grades: BCC + no nickel = lighter than austenitic
Ferritic stainless steels have a body-centred cubic (BCC) crystal structure — the same as plain carbon steel and pure iron. They contain 11–27% chromium and typically less than 1% nickel. The BCC structure packs atoms less efficiently than FCC (68% vs. 74%), and the absence of high-density nickel means no upward pull on density.
The result: ferritic stainless steel at 7,650–7,750 kg/m³ is noticeably lighter than austenitic grades. Type 430 (7,720 kg/m³) is approximately 210 kg/m³ lighter than 304 (7,930 kg/m³) — a difference of about 2.7%.
For a large panelling job where both 304 and 430 are candidates, that 2.7% density difference translates directly to a 2.7% weight difference. For thin-gauge decorative trim in 430, it matters. For a heavy structural plate where grade is driven by corrosion requirements, it’s irrelevant.
Martensitic grades: BCT lattice — a small density uptick from hardening
Martensitic stainless steels are hardened by quenching from the austenite region. The rapid cooling traps carbon in a supersaturated solution, producing a body-centred tetragonal (BCT) lattice — a BCC structure stretched along one axis by the forced carbon. The BCT structure in hardened martensite is slightly denser than the annealed BCC structure it transforms from, by less than 1%.
In practice, density data for martensitic stainless is typically given for the annealed or soft-annealed condition, where the structure is BCC: approximately 7,700–7,730 kg/m³ for 410, 420, and 440 grades. The hardened-and-tempered density is the same for any practical weight calculation.
The high carbon in 440C (0.95–1.20%) reduces density slightly below 410, for the same reason carbon reduces density in plain carbon steel. The combined effect of high carbon and high chromium (both lighter than or close to iron in density) brings 440C to approximately 7,700 kg/m³, slightly below 410 at 7,730 kg/m³.
Duplex grades: engineered at the midpoint
Duplex stainless steels are specifically designed to contain approximately 50% austenite and 50% ferrite by volume. The composition is tuned — with nitrogen to stabilize austenite and chromium/molybdenum to build corrosion resistance — so that neither phase dominates.
The density reflects this by design. 2205 duplex (7,805 kg/m³) sits between austenitic 304 (7,930) and ferritic 430 (7,720). The exact position within that range depends on the austenite-to-ferrite ratio, which is set by the Cr/Ni/Mo/N balance. Super-duplex 2507 is slightly denser than 2205 because it carries more nickel (6–8% vs. 4.5–6.5%) and more molybdenum.
For fabrication weight estimates, 7,800–7,820 kg/m³ covers all standard and super-duplex grades without meaningful error.
PH grades: ageing hardens without adding mass
Precipitation-hardening grades begin as austenitic, semiaustenitic, or martensitic alloys that are solution-treated and then aged at intermediate temperature. During ageing, fine intermetallic precipitates (copper-rich particles in 17-4 PH, NiAl precipitates in PH 13-8 Mo) form within the matrix.
These precipitates dramatically increase yield strength — 17-4 PH in the H900 condition reaches approximately 1,170 MPa yield — but they do not measurably change density. The precipitate particles are dispersed at the nanometer scale and make up a small fraction of the total volume. The density of aged 17-4 PH and solution-treated 17-4 PH are identical at 7,780 kg/m³.
17-4 PH, 15-5 PH, and 17-7 PH all have martensitic or martensitic-austenitic structures at room temperature after processing. Their density values (7,760–7,810 kg/m³) reflect this BCC/BCT-dominant microstructure — lighter than austenitic, slightly heavier than plain ferritic because of higher nickel content.
The Density Hierarchy — A Visual Summary
Reading from heaviest to lightest among stainless families:
| Rank | Family | Representative Grade | Density (kg/m³) | vs. 304 |
|---|---|---|---|---|
| 1 | High-alloy austenitic | AL-6XN (N08367) | 8,060 | +130 (+1.6%) |
| 2 | Standard austenitic | 316 / 316L | 7,980 | +50 (+0.6%) |
| 3 | Standard austenitic | 304 / 304L | 7,930 | — Reference |
| 4 | Low-Ni austenitic (200-series) | 201 | 7,880 | −50 (−0.6%) |
| 5 | Duplex | 2205 | 7,805 | −125 (−1.6%) |
| 6 | PH martensitic | 17-4 PH, 15-5 PH | 7,780 | −150 (−1.9%) |
| 7 | Ferritic | 430 | 7,720 | −210 (−2.6%) |
| 8 | Ferritic (high-Cr) | 446 | 7,650 | −280 (−3.5%) |
The total spread across all stainless families is approximately 410 kg/m³ — from 446 ferritic at 7,650 to AL-6XN at 8,060. For most fabrication work, the 304-to-316 comparison (50 kg/m³ difference) is what matters. For assemblies that mix austenitic and ferritic grades, the 210 kg/m³ spread is large enough to appear in careful weight budgets.
Stainless Steel Density vs. Other Structural Materials
| Material | Density (kg/m³) | Compared to 304 SS |
|---|---|---|
| Aluminum 6061 | 2,700 | 34% — steel is 2.9× heavier |
| Titanium Ti-6Al-4V | 4,430 | 56% |
| Carbon steel A36 | 7,850 | 99% — SS is 1% heavier |
| 304 / 304L stainless | 7,930 | — Reference |
| 316 / 316L stainless | 7,980 | +0.6% |
| Nickel (pure) | 8,908 | +12% |
| Copper | 8,960 | +13% |
The headline fact: stainless steel and carbon steel are within 1% of each other in density. 304 stainless at 7,930 kg/m³ is about 80 kg/m³ heavier than A36 at 7,850 kg/m³. For freight calculations on a mixed carbon-and-stainless assembly, you can use 7,900 as a blended approximation for the entire assembly and introduce less than 0.5% error in either direction.
Where “7,900 kg/m³” Comes From — and When to Use It
Some references cite 7,900 kg/m³ as the density of stainless steel without specifying a grade. This is a rounding of the 304 value (7,930) and sits within the range of austenitic stainless steel as a family (7,880–8,060 for standard grades).
Use 7,900 when:
- Grade is unspecified, and the assembly is likely austenitic stainless
- You need a single value for a mixed-grade stainless assembly, and a blended estimate is acceptable
- A quick sanity check is needed, and precision is less important than speed
Use grade-specific density when:
- The assembly includes ferritic stainless (430, 409) — these are 200–300 kg/m³ lighter than austenitic
- The assembly includes duplex grades — intermediate density that rounds neither to 304 nor to ferritic
- Weight specifications on the drawing have tight tolerances
- Freight classification is near a tier boundary
- You are designing lifting equipment rated to a specific safe working load
I have seen the consequences of using 7,930 for an assembly that contained 40% Type 430 ferritic panels. The freight estimate was 3% high; the customer’s lifting fixture was designed to a weight that was 28 kg heavier than reality. The fixture worked, but the over-engineering was unnecessary and cost money on a custom-built handling system.
Learn more:
Engineer’s Guide: Is Stainless Steel Magnetic? Explaining Different Grades
Frequently Asked Questions About Stainless Steel Density
Q: What is the density of stainless steel in kg/m³?
It depends on the grade family. Standard austenitic stainless (304, 316): approximately 7,930–7,980 kg/m³. Ferritic stainless (430, 409): approximately 7,650–7,750 kg/m³. Duplex (2205): approximately 7,800–7,820 kg/m³. PH grades (17-4 PH): approximately 7,760–7,810 kg/m³. If the grade is unspecified and likely austenitic, use 7,900 kg/m³ as a working approximation.
Q: Is stainless steel denser than carbon steel?
Standard austenitic stainless (304 at 7,930 kg/m³) is approximately 1% denser than A36 carbon steel (7,850 kg/m³). Ferritic stainless (430 at 7,720 kg/m³) is approximately 1.7% lighter than A36. The difference is small in all cases — the two materials are close enough that using a single value (7,900 or 7,850) for a mixed assembly introduces negligible error for most purposes.
Q: What is the density of 316 stainless steel?
7,980 kg/m³ (7.98 g/cm³, 0.288 lb/in³). The 2–3% molybdenum addition in 316 (density of Mo: 10,280 kg/m³) raises the density about 50 kg/m³ above 304. For most weight calculations, the difference from 304 is negligible. The reason to specify 316 over 304 is chloride pitting resistance, not weight.
Q: Does heat treatment change stainless steel density?
No, not meaningfully for practical calculations. Solution annealing, quenching, and aging treatments change microstructure and mechanical properties. The volume change across heat treatment conditions for stainless is less than 1% — within rounding tolerance for any weight or freight estimate.
Q: Why is Type 430 ferritic stainless lighter than 304?
Two reasons that work in the same direction. First, 430 has a body-centred cubic (BCC) crystal structure, which packs atoms less efficiently than the face-centred cubic (FCC) structure of austenitic 304 — 68% vs. 74% space utilisation. Second, 430 contains essentially no nickel (≤0.75%), while 304 contains 8–11% nickel (density 8,908 kg/m³). The absence of nickel removes the main upward density driver in austenitic stainless. Both effects together lower 430’s density to 7,720 kg/m³ — about 210 kg/m³ below 304.
Q: What is the density of 17-4 PH stainless steel?
7,780 kg/m³ (7.78 g/cm³, 0.281 lb/in³). This value applies across all ageing conditions — H900, H925, H1025, H1075, H1100, H1150. Precipitation hardening dramatically increases yield strength (from ~520 MPa solution-treated to ~1,170 MPa at H900) but does not change density. The fine intermetallic precipitates formed during ageing make up too small a volume fraction to affect bulk density.
Q: What is the density of stainless steel in lb/in³?
304 / 304L: 0.286 lb/in³. 316 / 316L: 0.288 lb/in³. 430 ferritic: 0.279 lb/in³. 2205 duplex: 0.282 lb/in³. 17-4 PH: 0.281 lb/in³. For a single all-purpose stainless value in imperial units, 0.286 lb/in³ covers most austenitic grades accurately.
References
- ASM Handbook, Volume 1: Properties and Selection — Irons, Steels, and High-Performance Alloys, 10th Edition. ASM International, Materials Park, OH, 1990 (4th printing 1995). (Physical properties by stainless steel family including density; crystal structure data for austenitic, ferritic, martensitic, and duplex grades; precipitation-hardening stainless properties by aging condition.)
- ASTM A240/A240M-22, Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications, ASTM International, 2022. (Table 1 chemical composition limits for all covered grades — basis for the Cr, Ni, Mo content values cited in all grade density discussions; UNS designations; duplex grade composition limits including 2205 S32205 vs. S31803 distinction.)
- ASTM A480/A480M-22a, Standard Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip, ASTM International, 2022. (General requirements framework referenced by A240; density values consistent with standard mill certification practice.)
- Michael Smith Engineers Limited, Material Grade Comparison Table (DIN / BS / USA / Japan equivalences). Available at michaelsmithengineers.co.uk. (Cross-reference for European DIN and British BS stainless grade equivalents; approximate equivalences only — compositions should be verified against applicable national standard for procurement.)
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