If you have ever picked up two equal-sized metal bars and one felt heavier, that is density in action. Density describes how tightly packed the atoms in a material are, and it helps you make the right alloy selection. Follow along to learn about the density of various steel grades.
What is Density and Why Does It Matter for Steel?
Definition of Density
Density indicates how heavy your object is. In other words, it expresses the mass per unit volume of an object. The mathematical formula for calculating density is.
Density = Mass/Volume
The standard units of density are as follows:
- Kg/m³: Kilogram per meter. This is the standard SI unit for density, and it is the best for large-scale projects or designs.
- g/cm³: Grams per cubic meter. It is widely used in laboratories and educational programs.
- Lb/in³): Pounds per cubic inch. This is the most popular unit of density in the United States. It is also favored by manufacturers and machinists.
Importance in Engineering Applications
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- Structural load calculations: material density data allows you to make load-bearing calculations with utmost precision. In fact, engineers use density data to ensure alloys perform as expected under loads and that the alloy complies with safety regulations.
- Material selection considerations: The same logic applies to fabricators and CNC machinists. The density of steel and other alloys affects key project parameters, such as part handling, tool wear, and machining load.
- Transportation and logistics planning: In transportation, every kilogram saved translates to more fuel efficiency and less operating costs.
- Cost estimation: Using alloy density data, material buyers can reliably estimate the cost of material and shipping. Especially when the material is sold by weight.
Standard Density of Steel
The average density of steel is 7850 kg/m³. Here’s a table of the density of steel expressed in different units of measurement.
Typical Steel Density Values
| Unit | Avg. Steel Density |
| kg/m³ | 7,850 kg/m³ |
| g/cm³ | 7.85 g/cm³ |
| lb/in³ | 0.284 lb/in³ |
| lbs/ft³ | 490 lbs/ft³ |
Specific Gravity of Steel
Specific gravity describes the weight of your steel compared to water. Water has a constant specific gravity of one. It is a way for engineers to compare materials quickly without having to convert between units. Most steels exhibit a specific gravity of 7.75 to 8.05.
Factors Affecting Steel Density
Although steel has an average density of 7.85 g/cm³, the precise density of any steel varies slightly. These variations are first based on alloy composition, so steels that contain tungsten, chromium, molybdenum, and other elements will be denser than pure steel.
But the crystalline lattice of your alloy also has an impact on its specific density. For instance, austenitic 304 and 316 are the densest steels, with a density of 8000 kg/m³. These alloys have a face-centered cubic structure with more atoms packed per cubic meter.
Ferritic 410 steel, in contrast, is the lightest steel with a density of 7,750 kg/m³. This steel has a body-centered tetragonal structure acquired during heat treatment.
Lastly, the density of your steel is not constant. It fluctuates ever so slightly based on your service environment’s temperature and pressure. Therefore, when there is an increase in heat, the density of your steel reduces as atoms excite and take up more space.
Density of Different Steel Types
Here we compare the densities of different steels.
Carbon Steel Density
| Carbon steel grade | Density |
| Low carbon steel | 7,850 kg/m³ |
| Medium carbon steel | 7,840 kg/m³ |
| High carbon steel | 7,840 kg/m³ |
The density of carbon steel ranges between 7,840 kg/m³ and 7,850 kg/m³, depending on the carbon concentration.
Mild Steel (MS) Density
Mild steel offers an average density of about 7,850 kg/m³, which is the same as pure carbon steel. When you work with mild steel pipes or hollow sections, the density itself doesn’t change. But factors like wall thickness affect the overall weight per meter of your MS pipes.
For instance, a thinner MS pipe weighs less because more of its volume is air. However, the material density inside the steel wall remains constant at 7,850 kg/m³. For mild steel bars and rods, density also stays the same, though total weight varies by shape and size.
Structural Steel Density
| Structural steel grade | Density |
| A36 | 7,850 kg/m³ |
| A572 | 7,850 kg/m³ |
As the name implies, structural steel is best suited for architectural applications. Specific grades like A572 and A36 steels offer an average density of 7,850 kg/m³.
Stainless Steel Density
| Stainless steel grade | Density |
| SS304 | 8,000 kg/m³ |
| SS316 | 8,000 kg/m³ |
As you learned earlier, 304 and 316 stainless steels are the most dense types of steel. They offer an average density of 7,930 kg/m³ or 8000 kg/m³, rounded to the nearest zero. In comparison, carbon steel has a density of 7.85 g/cm³ because it contains fewer elements.
Alloy and Specialty Steels
Corten steel has a density of 7,850 kg/m³, similar to standard carbon steel. What makes it unique isn’t its density but its weathering resistance.
Tool steels, on the other hand, have an average density of 7,760 kg/m³. But M2 tool steel can achieve a density of 8,160 kg/m³. Lastly, high-strength low-alloy (HSLA) steels are marginally lighter than pure steel, with a density range of 7,700 to 7,850 kg/m³.
Steel Density vs. Iron Density
Is steel denser than iron? Let’s find out.
Pure Iron Density
Iron has an average density of 7,875 kg/m³, just slightly higher than most steel grades. The only steels with a higher density than iron are austenitic, corten steel, and M2 tool steel.
Cast Iron Density
Cast iron exhibits a relatively wide density range due to microstructure changes acquired during casting. Below is a table of common cast irons and their densities.
| Cast iron grade | Density |
| Gray cast iron | 7,200 kg/m³ |
| Ductile cast iron | 7,100 kg/m³ |
| Molten cast iron | 6,800-7,000 kg/m³ |
Key Differences
The primary reasons why steel and iron exhibit different densities are their alloy composition and atomic structure. Pure iron has a ferritic body-centered cubic structure that is magnetic, while the microstructure of your steel may vary from austenitic, martensitic, ferritic, or duplex.
Steel Density at Different Temperatures
Here’s how the density of steel alters at different temperatures.
Temperature Effects on Density
When you heat steel, your metal expands, causing atoms to occupy more space. As a result, the density of your steel may reduce fractionally. Steel has a thermal expansion coefficient of 12 × 10⁻⁶ per °C, meaning for every degree rise in temperature, your steel expands by 0.2%.
Liquid State Density
Steel has a melting point of 1,370-1,540°C. At this temperature, your steel transitions into a liquid state and its density drops to around 6,900-7,200 kg/m³. This reduction happens because atomic bonds gradually loosen, thereby increasing the space between atoms.
Practical Implications
When you understand steel’s density at different temperatures, you can accurately perform thermal calculations for your project. For instance, in high-temperature applications such as heat sinks, density affects thermal expansion, load estimates, and structural performance.
Comprehensive Steel Density Comparison Chart
| Steel Type | Density (kg/m³) | Density (g/cm³) | Density (lb/in³) | Density (lb/ft³) | Specific Gravity |
| Carbon Steel (Low) | 7,850 | 7.85 | 0.284 | 490 | 7.85 |
| Carbon Steel (Medium) | 7,840 | 7.84 | 0.283 | 489 | 7.84 |
| Carbon Steel (High) | 7,840 | 7.84 | 0.283 | 489 | 7.84 |
| Mild Steel (MS) | 7,850 | 7.85 | 0.284 | 490 | 7.85 |
| Structural Steel (A36) | 7,850 | 7.85 | 0.284 | 490 | 7.85 |
| Structural Steel (A572) | 7,850 | 7.85 | 0.284 | 490 | 7.85 |
| Stainless Steel 304 | 8,000 | 8.00 | 0.289 | 500 | 8.00 |
| Stainless Steel 316 | 8,000 | 8.00 | 0.289 | 500 | 8.00 |
| Stainless Steel 410 | 7,750 | 7.75 | 0.280 | 484 | 7.75 |
| Stainless Steel 430 | 7,800 | 7.80 | 0.282 | 487 | 7.80 |
| Corten Steel (Weathering) | 7,850 | 7.85 | 0.284 | 490 | 7.85 |
| Tool Steel (D2) | 7,760 | 7.76 | 0.280 | 484 | 7.76 |
| Tool Steel (M2) | 8,160 | 8.16 | 0.295 | 509 | 8.16 |
| Spring Steel | 7,850 | 7.85 | 0.284 | 490 | 7.85 |
| Galvanized Steel | 7,850 | 7.85 | 0.284 | 490 | 7.85 |
Density Calculations
You can make these calculations using density.
Weight Calculation Using Density
Density is useful for calculating the weight of your component in seconds. Just use the formula. Weight = Volume X Density
Let’s put that into perspective. If you have a carbon steel bar with a volume of 0.01 m³, multiply 0.01 by the density of your steel. Since the density of carbon steel is 7,850 kg/m³, it means the weight of your steel bar is approximately 78.5 kg.
When dealing with pipes or hollow sections, you calculate the volume of steel by subtracting the inner volume from the outer, then multiplying by density.
Load-Bearing Calculations
During construction, density can help you determine dead loads, which refer to the constant weight of your appliance. If you’re designing beams, columns, or trusses, using accurate density values is the best way to ensure your alloy selection meets all safety standards.
Material Cost Estimation
Density is also a powerful tool for budgeting and logistics. By knowing how much steel weighs per meter, you can estimate total material costs before fabrication begins. This same calculation applies to transportation planning, since shipping fees often depend on total weight.
Common Misconceptions About Steel Density
Here we debunk common misconceptions about the density of steel, including
- “All steel has the same density”: No. Most steels have an average density of 7850 kg/m³. However, some steels may be lighter or heavier.
- “Stronger steel is always denser”. Nope. The mechanical strength of your steel has more to do with alloying and heat treatment than density. For instance, HSLA steels are almost the same weight as pure steel. Yet, they are nearly twice as strong.
- “Stainless steel is lighter than carbon steel“: No. It is actually the other way round. Austenite stainless steels are denser than your regular carbon steel. This is because it is made up of more alloying elements. In comparison, the only stainless steels lighter than carbon steel are 410 and 430..
Conclusion
Density tells you how heavy an object is. If you are working with steel, density directly affects decisions related to the design, fabrication or machining of your appliance. By understanding the densities of various steels, you will have an easy time selecting the right grade for your job.
FAQs
Is steel heavier than aluminum?
Aluminum has a density of 4700 kg/m³. Therefore, steel is heavier than aluminum.
Does steel density change when it rusts?
No, rust does not directly change the density or mass of your steel.
How do you measure steel density at home?
You can roughly measure density using a weighing scale and a water displacement method. First, weigh your steel sample in kilograms. Then, submerge it in a graduated container filled with water and measure the volume of displaced water in cubic meters or liters. Next, divide the mass by the displaced volume to get an approximate density value (ρ = m/V).
Does galvanized steel have a different density?
No. Galvanized steels have the same density as pure steel.
Can steel density vary within the same grade?
Yes, the density of steels may vary within the same grade. But that is only to a tiny extent. These changes are often picked up during thermal processing or manufacturing. For instance, casting can create microscopic holes in your steel, slightly reducing density.
What affects steel density more: carbon or chromium?
Chromium has a greater effect than carbon on the density of steel because it’s a heavier element. When added in large amounts (as in stainless steels), it can slightly increase density.
Is recycled steel less dense than virgin steel?
No. Recycled steel has the same crystal structure and alloying composition as virgin steel. Unless impurities are introduced during the recycling process, the density remains unchanged.
Steel vs Concrete: Which is denser
Typical reinforced concrete has a density of about 2,400 kg/m³, while steel has an average density of around 7,850 kg/m³. Therefore, steel is about three times heavier than concrete.
Related articles:
Is Titanium Stronger Than Steel? A Complete Guide
Does Steel Rust? Causes, Prevention, and Best Practices in Manufacturing
Melting Point of Steel– A Smart Selection Guide for Fabricators
