Density of Aluminum by Alloy: lb/in3, lb/ft3, g/cm3, and kg/m3
By Bilbo Baggins
The density of 6061 aluminum is 2.70 g/cm3, equal to 0.0975 pounds per cubic inch, 168.6 pounds per cubic foot, or 2700 kilograms per cubic meter. That is the number most people are looking for. But aluminum is not one material, and density across common alloys runs from about 2.66 g/cm3 for 5083 up to 2.83 for 7050, a spread of about 6 percent. On a full mill plate that spread is tens of pounds, and on a weight-critical design it is a real number. This is the complete table with every unit conversion, plus what actually drives the variation.
In Short
- →6061 aluminum is 2.70 g/cm3, which is 0.0975 lb per cubic inch, 168.6 lb per cubic foot, or 2700 kg per cubic meter.
- →Density varies by alloy from about 2.66 g/cm3 for 5083 up to 2.83 for 7050, a spread of roughly 6 percent.
- →The 7xxx alloys are the heavy end because zinc is denser than aluminum. The 5xxx alloys are the light end because magnesium is lighter.
- →Use 0.0975 lb/in3 for 6061 and 6063, and 0.102 for 7075 and 7050. Those two numbers cover most of what gets bought.
- →Aluminum is roughly one third the density of steel, at 0.0975 against about 0.284 lb per cubic inch for A36.
- →Density does not change with temper. 6061-T6 and 6061-T651 have the same density, because heat treatment rearranges the microstructure without changing the composition.
Density by Alloy, All Units
The conversion factors, if you want to check the arithmetic: 1 g/cm3 equals 0.0361273 lb/in3, 1 lb/in3 equals 1728 lb/ft3, and 1 g/cm3 equals 1000 kg/m3.
| Alloy | g/cm3 | lb/in3 | lb/ft3 | kg/m3 |
|---|---|---|---|---|
| 5083 | 2.66 | 0.0961 | 166.1 | 2660 |
| 5052 | 2.68 | 0.0968 | 167.3 | 2680 |
| 6061 | 2.70 | 0.0975 | 168.6 | 2700 |
| 6063 | 2.70 | 0.0975 | 168.6 | 2700 |
| 1100 (commercially pure) | 2.71 | 0.0979 | 169.2 | 2710 |
| 2024 | 2.78 | 0.1004 | 173.5 | 2780 |
| Cast tool and jig | 2.80 | 0.101 | 174.8 | 2800 |
| 7075 | 2.81 | 0.1015 | 175.4 | 2810 |
| 7050 | 2.83 | 0.1022 | 176.7 | 2830 |
Why Alloys Differ
Pure aluminum is 2.70 g/cm3. Every alloy is aluminum plus deliberate additions, and each addition moves the density in the direction of its own.
- Zinc is about 7.14 g/cm3, far denser than aluminum. The 7xxx alloys carry several percent zinc, which is why 7075 and 7050 sit at the heavy end.
- Copper is about 8.96 g/cm3. That is why 2024, a copper alloy, is heavier than 6061 despite not being a 7xxx.
- Magnesium is about 1.74 g/cm3, lighter than aluminum. The 5xxx alloys are magnesium-based, which is why 5052 and 5083 are the lightest common alloys.
- Silicon is about 2.33 g/cm3, slightly lighter. 6061 is a magnesium-silicon alloy, which is why it sits essentially at the density of pure aluminum.
Temper Does Not Change Density
A common question worth answering directly. 6061-T6, 6061-T651, and 6061-O all have the same density.
- Heat treatment changes the microstructure and the distribution of precipitates. It does not change what elements are present or how much of each.
- So T651 and T6 weigh exactly the same for identical dimensions, and the strength difference between them has no weight cost.
- The same applies to 7075-T651 versus 7075-T7351. Different properties, identical density.
- This matters when substituting tempers: you can move to a stress-relieved temper for machining stability without any weight penalty.
Aluminum Against Other Metals
The comparison that drives most material selection conversations.
| Material | lb/in3 | g/cm3 | Relative to 6061 |
|---|---|---|---|
| 6061 aluminum | 0.0975 | 2.70 | 1.00x |
| Ti-6Al-4V titanium | 0.160 | 4.43 | 1.64x |
| A36 carbon steel | 0.284 | 7.85 | 2.91x |
| 304 stainless steel | 0.289 | 8.00 | 2.96x |
| Copper | 0.324 | 8.96 | 3.32x |
Using Density Correctly
Three practical applications, and one place people get it wrong.
- Weight and freight. Multiply volume by density before ordering so you know whether the piece ships parcel or LTL.
- Cost estimating. Metal is priced by weight, so density converts your part dimensions into a material budget.
- Buy-to-fly. The ratio of purchased to finished material is a volume ratio, and density turns it into dollars.
- Where people go wrong: using density to compare alloys for a weight-critical design. What matters there is specific strength, strength divided by density. 7075-T651 is denser than 6061-T6 and still gives a lighter part, because it is far stronger per unit weight.
Use 0.0975 lb per cubic inch for 6061 and 0.102 for 7075 and 7050 and you will be right for the vast majority of aluminum you buy. Remember that temper does not affect density, that the 5xxx alloys are slightly lighter and the 7xxx slightly heavier, and that for weight-critical design the number to compare is specific strength rather than density alone.
Frequently Asked Questions
What is the density of aluminum in lb/in3?
6061 aluminum is 0.0975 lb per cubic inch. Across common alloys the range is roughly 0.0961 for 5083 to 0.102 for 7050. Pure aluminum is about 0.0979.
What is the density of aluminum in g/cm3?
2.70 g/cm3 for 6061 and for pure aluminum. Common alloys range from 2.66 for 5083 to 2.83 for 7050, a spread of about 6 percent.
Does aluminum temper affect density?
No. 6061-T6, 6061-T651, and 6061-O all have the same density. Heat treatment changes microstructure, not composition, so tempers of the same alloy weigh identically for identical dimensions.
How much lighter is aluminum than steel?
6061 aluminum is about 0.0975 lb per cubic inch against roughly 0.284 for A36 carbon steel, so aluminum is about 66 percent lighter by volume, or roughly one third the density. For the same part the saving is usually smaller, because matching stiffness requires more aluminum section.
Which aluminum alloy is the lightest?
Among common structural alloys, 5083 at 2.66 g/cm3 and 5052 at 2.68 are the lightest. The difference against 6061 at 2.70 is small, so pick the alloy on properties and choose 5xxx for weight only when the design is genuinely marginal.
Density to dollars
Turn dimensions into weight and price.
Calculate the weight of your exact piece, then price the same rectangle cut to size with mill certs included.