Density of Steel: Values by Grade, Comparisons, and Engineering Use
Steel density usually falls between 7,750–8,050 kg/m³, with 7,850 kg/m³ used as the most common engineering reference. That value represents the average density of carbon steel in everyday structural and fabrication work.
Different steel types, including carbon steel, stainless steel, and tool steel, vary slightly because their alloying elements differ. This page gives exact values, major grade comparisons, the steel-vs-aluminum weight difference, and a practical method for estimating steel weight with the material density calculator.
Key values
Steel Density: Key Values
kg/m³
7,850 kg/m³
Carbon steel average reference
g/cm³
7.85 g/cm³
Most common engineering reference
lb/ft³
489.8 lb/ft³
U.S. structural engineering reference
7,850 kg/m³ is the standard engineering reference for carbon steel.
Actual values range from 7,750 to 8,050 kg/m³ depending on alloy composition.
Grades
Steel Density by Grade and Type
Steel is an alloy of iron and carbon, and it often contains manganese, chromium, nickel, and other elements. The type and proportion of alloying elements determine final density, but the variation is relatively small.
| Steel Type | Typical Density | Key Alloying Elements | Common Use |
|---|---|---|---|
| Low-carbon steel (mild steel) | 7,850 kg/m³ | C < 0.3% | Structural, sheet metal |
| Medium-carbon steel | 7,850 kg/m³ | C 0.3–0.6% | Machinery, axles |
| High-carbon steel | 7,830 kg/m³ | C 0.6–1.0% | Springs, cutting tools |
| Stainless steel 304 | 8,000 kg/m³ | 18% Cr, 8% Ni | Food equipment, architecture |
| Stainless steel 316 | 8,000 kg/m³ | 16% Cr, 10% Ni, 2% Mo | Marine, medical |
| Stainless steel 430 | 7,800 kg/m³ | 17% Cr | Appliances, automotive trim |
| Tool steel (H13) | 7,800 kg/m³ | Cr, Mo, V | Dies, molds |
| High-speed steel (M2) | 8,160 kg/m³ | W, Mo, Cr, V | Cutting tools |
| Cast iron (gray) | 7,200 kg/m³ | C 2.5–4%, Si | Engine blocks, pipes |
Cast iron is listed for comparison. Although related to steel, it is a distinct material with higher carbon content and different mechanical properties.
For broader material lookup, open the density table.
Alloy effects
Why Does Steel Density Vary by Grade?
Steel starts from an iron matrix. The density of iron is 7,874 kg/m³, so steel remains close to that value unless alloying elements shift the final composition. Related comparison terms include density of iron, and the general concept is explained in what is density.
Chromium (7,190 kg/m³) and manganese (7,470 kg/m³) are lighter than iron, so they slightly reduce density when added. Nickel (8,908 kg/m³) and molybdenum (10,280 kg/m³) are heavier than iron, so they slightly increase it.
Stainless steel 304 contains 18% chromium and 8% nickel, so those effects partially offset each other. The final density is about 8,000 kg/m³, slightly higher than carbon steel at 7,850 kg/m³. In practical engineering, 7,850 kg/m³ is accurate enough for estimating most steel grades.
Steel vs aluminum
Density of Steel vs Aluminum
Steel and aluminum density comparison is one of the most common decisions in engineering material selection. It directly controls part weight and the strength tradeoffs behind the choice; related comparison terms include density of aluminum.
| Steel (carbon) | Aluminum (pure) | |
|---|---|---|
| Density | 7,850 kg/m³ | 2,700 kg/m³ |
| g/cm³ | 7.85 | 2.70 |
| lb/ft³ | 489.8 | 168.6 |
| Relative weight | 1× (baseline) | 0.34× (66% lighter) |
- Aircraft and automotive: Aluminum alloys replace steel in weight-sensitive structures. A same-volume aluminum part weighs about one-third of its steel equivalent.
- Structural construction: Steel's higher density comes with higher strength, making it the default choice for beams, columns, and reinforcement where stiffness per unit volume matters more than weight.
- Bicycles and consumer products: Aluminum frames are standard where weight reduction justifies the higher material cost per kg.
Examples
Steel Weight Estimation: Practical Examples
Using density makes it possible to estimate steel weight quickly without weighing the part directly.
Example 1 — Steel plate weight
A steel plate measuring 2 m × 1 m × 0.01 m (10 mm thick):
Volume = 2 × 1 × 0.01 = 0.02 m³
Mass = 7,850 × 0.02 = 157 kg
Example 2 — Steel rod weight
A steel rod 3 m long with 50 mm diameter:
Volume = π × (0.025)² × 3 = 0.00589 m³
Mass = 7,850 × 0.00589 = 46.2 kg
Example 3 — Steel vs aluminum comparison
Same plate as Example 1, but in aluminum (2,700 kg/m³):
Mass = 2,700 × 0.02 = 54 kg
Steel version is 2.9× heavier than aluminum at equal volume.
FAQ
Frequently Asked Questions
What is the density of steel in kg/m³?
The standard engineering reference for carbon steel is 7,850 kg/m³. Depending on the grade, actual values range from about 7,750 kg/m³ for some stainless grades to 8,160 kg/m³ for certain high-speed tool steels. For most structural calculations, 7,850 kg/m³ is the accepted default.
What is the density of stainless steel?
The most common stainless steel grades (304 and 316) have a density of about 8,000 kg/m³, slightly higher than carbon steel at 7,850 kg/m³. The difference comes from the nickel content, which is denser than iron, partially offset by chromium, which is slightly less dense than iron.
How does steel density compare to aluminum?
Steel is about 2.9 times denser than aluminum. Carbon steel is 7,850 kg/m³ while pure aluminum is 2,700 kg/m³. This means an aluminum part of the same volume weighs roughly one-third as much as its steel equivalent, which is why aluminum is preferred in aerospace and automotive applications where weight matters.
What is the density of steel in lb/ft³?
Carbon steel has a density of approximately 489.8 lb/ft³. Stainless steel 304 is about 499.4 lb/ft³. These values are commonly used in U.S. structural engineering and HVAC load calculations.
Does temperature affect steel density?
Yes, but only slightly at normal operating temperatures. Steel expands when heated, so density decreases marginally. At 200°C, carbon steel density drops to roughly 7,800 kg/m³. For most structural applications this change is negligible, but it matters in high-temperature process equipment and furnace design.