The density of solid aluminum at room temperature is about 2.70 g/cm³. That equals 2,700 kg/m³, 0.0975 lb/in³, or 168.6 lb/ft³. The Royal Society of Chemistry lists 2.70 g/cm³ for the element at room temperature.
Use 2.70 g/cm³ for an initial weight estimate when the grade is unknown. Use an alloy-specific value for a released drawing, shipping plan, or mass-critical design. The selected common grades below range from 2.66 to 2.81 g/cm³.
Density is only one input. It does not prove an alloy grade or predict strength by itself. Finished mass also depends on net geometry, cavities, coatings, inserts, and process-related porosity.
Aluminum density quick reference
| Unit | Typical value for solid aluminum at room temperature |
|---|---|
| g/cm³ | 2.70 |
| kg/m³ | 2,700 |
| kg/L | 2.70 |
| g/mm³ | 0.00270 |
| lb/in³ | 0.0975 |
| lb/ft³ | 168.6 |
These values are conversions of the same rounded base value. They are not separate measurements.
Density and specific gravity are related, but they are not the same quantity. Density has units. Specific gravity is a dimensionless ratio to a reference fluid, usually water. Aluminum’s nominal specific gravity is about 2.7 under common reference conditions.
Watch the cubic unit. Aluminum is 2,700 kg/m³, not 2.70 kg/m³. A missing factor of 1,000 creates a serious mass error.
Why do sources show 2.6989, 2.70, 2.71, or 2.712 g/cm³?
The numbers can differ without describing a real conflict. First check what material and condition the source means.
The NIST STAR composition page lists elemental aluminum at 2.69890 g/cm³. Rounding that value to three significant figures gives 2.70 g/cm³. Many engineering references use that convenient number.
A 2.71 g/cm³ value may reflect a commercial-purity grade, selected table, or different rounding. For example, the alloy table below lists 1100 aluminum at 2.71 g/cm³. A generic value of 2.712 g/cm³ should not be applied automatically to every aluminum alloy.
Four details explain most differences:
- Material scope: elemental aluminum, commercial-purity aluminum, and an alloy are not identical.
- Alloy chemistry: Magnesium-rich grades can sit below 2.70 g/cm³. Copper- or zinc-bearing grades often sit above it.
- Temperature and condition: thermal expansion changes volume, and material condition can shift a precise value.
- Rounding: 2.69890, 2.699, and 2.70 may be the same source value at different precision.
For estimating, match the number of significant digits to the quality of the inputs. A six-decimal density does not improve a mass estimate based on rough dimensions.
Density of common aluminum alloys
The values below come from Table 7 in the NIST-hosted ASM Handbook chapter on aluminum mill products. They are nominal densities for the annealed, or O, temper.
| Wrought alloy | Nominal density (g/cm³) | Nominal density (kg/m³) | Practical reading |
|---|---|---|---|
| 1050 | 2.705 | 2,705 | Commercially pure; close to elemental aluminum |
| 1100 | 2.71 | 2,710 | Commercially pure general-purpose grade |
| 2024 | 2.78 | 2,780 | Copper-bearing alloy; above 6xxx values |
| 3003 | 2.73 | 2,730 | Manganese-bearing sheet alloy |
| 5052 | 2.68 | 2,680 | Magnesium-bearing sheet alloy |
| 5083 | 2.66 | 2,660 | Higher-magnesium marine alloy |
| 6061 | 2.70 | 2,700 | Common structural and machining alloy |
| 6063 | 2.70 | 2,700 | Common architectural extrusion alloy |
| 7075 | 2.81 | 2,810 | Zinc- and copper-bearing high-strength alloy |
The table also shows why density cannot identify every grade. Both 6061 and 6063 are listed at 2.70 g/cm³. Their real design differences concern chemistry, temper, strength, extrusion behavior, finish, and other properties.
Density also rarely decides between 5052 and 6061. Their nominal values differ by less than one percent. Product form and manufacturing route usually matter more, as this 5052 versus 6061 selection guide explains.
How composition and temperature affect aluminum density
Alloying changes both the mass and atomic arrangement within a given volume. The effect depends on the complete composition and phase condition. It is not accurate to add elemental densities with a simple arithmetic average.
The pattern is still useful for orientation. The 5xxx grades in the table sit at 2.66-2.68 g/cm³. The copper-bearing 2024 grade is 2.78 g/cm³, while 7075 is 2.81 g/cm³. Use the actual grade value rather than a series-level assumption.
Temperature changes density through thermal expansion. When aluminum heats, its volume grows while mass remains constant. Its density therefore falls. The change is small over ordinary room-temperature variation but matters in precise metrology and high-temperature processing.
The room-temperature value also does not apply to molten aluminum. Liquid density depends on alloy and melt temperature. Foundry calculations should use data for the actual melt condition, not 2.70 g/cm³ by default.
Heat treatment can alter phase distribution and a precise density value. For ordinary weight planning, the nominal alloy value is usually adequate. For a controlled density measurement, match the source to alloy, temper, temperature, and product condition.
How to calculate aluminum part weight
Use the relationship:
Mass = density × volume
Keep the units consistent. If density is in g/cm³, volume must be in cm³ and the result will be grams. If density is in kg/m³, volume must be in m³ and the result will be kilograms.
Common volume formulas are:
- Plate or rectangular bar: length × width × thickness
- Round bar: π × diameter² ÷ 4 × length
- Tube: π × (outside diameter² – inside diameter²) ÷ 4 × length
- Complex machined part: use the net solid volume from a verified CAD model
Worked example: 6061 aluminum plate
Assume a rectangular plate measures 500 mm × 300 mm × 10 mm.
- Volume = 500 × 300 × 10 = 1,500,000 mm³.
- Convert volume: 1,500,000 mm³ = 1,500 cm³.
- Use 6061 nominal density: 2.70 g/cm³.
- Mass = 1,500 × 2.70 = 4,050 g = 4.05 kg.
The 4.05 kg result is the unmachined rectangular volume. Holes, pockets, slots, and chamfers reduce it. Inserts and coatings add mass. A finished-part estimate should use the net CAD volume and model non-aluminum items separately.
Before accepting a CAD mass, check four items:
- The assigned material matches the specified alloy.
- The model uses the final geometry, not a stock envelope.
- Suppressed cavities, threads, and patterned features are present.
- The CAD unit system matches the density unit.
For logistics, also separate net part mass from packaging, pallets, coolant residue, and dunnage.
How aluminum compares with other metals
This table uses typical room-temperature values for screening. Exact grades vary.
Element values use RSC room-temperature entries for magnesium, aluminum, titanium, and copper. Steel entries are broad screening values from common engineering density tables, because both rows cover alloy families.
| Material | Typical density (g/cm³) | Mass versus equal-volume aluminum |
|---|---|---|
| Magnesium | 1.74 | 0.64× |
| Aluminum | 2.70 | 1.00× |
| Titanium | 4.51 | 1.67× |
| Carbon steel | 7.85 | 2.91× |
| Stainless steel | 7.5-8.0 | 2.78-2.96× |
| Copper | 8.96 | 3.32× |
An equal-volume aluminum object is about 34% of the mass of a typical carbon-steel object. That supports the familiar “about one-third” comparison.
Equal volume is not equal function. An aluminum replacement may need a different wall, rib, section, or joint design. Compare stiffness, strength, fatigue, corrosion, temperature, process, and cost before changing material. Density alone cannot establish the final weight saving. See the separate aluminum tensile-strength guide for that property boundary.
How to measure the density of an irregular aluminum part
For a solid part with complex geometry, the Archimedes method avoids a manual volume calculation. The Government of Canada procedure weighs the object in air and again while it is suspended in water.
Use this equation:
Density of object = mass in air ÷ (mass in air – apparent mass in water) × density of water
At 20°C, the procedure uses water density of 0.998 g/cm³. One sample weighs 110.18 g in air and 69.45 g in water. The calculated density is about 2.70 g/cm³.
For a useful check:
- Clean and dry the sample, then record its mass in air.
- Suspend it fully in water without touching the container.
- Remove visible air bubbles from the sample and suspension thread.
- Record water temperature and apparent immersed mass.
- Repeat the measurement and report the method and precision.
Coatings, hollow sections, trapped air, and open pores can invalidate a simple interpretation. Water entering surface-connected pores can make the displaced volume appear too small. The calculated density then appears too high.
A NIST study of porosity measurements in metal additive manufacturing documents this infiltration mechanism in porous metal samples. The study material was cobalt-chromium, not aluminum. The relevant transfer is the measurement caution, not its numerical results.
When a mass estimate becomes a manufacturing question
For a strict mass target, define the alloy, temper, net volume, coating, inserts, and acceptance condition first. Do the same when measured mass does not match CAD. Then send the drawing and requirements to Zheng Ji Aluminum for a focused manufacturing review.
Frequently asked questions
What density should I use for 6061-T6 aluminum?
Use 2.70 g/cm³ or 2,700 kg/m³ for a normal engineering mass estimate. The cited handbook table lists 6061 at 2.70 g/cm³ for O temper. Use a condition-specific supplier datasheet if density is a controlled requirement.
What is the density of 7075 aluminum?
The cited handbook gives a nominal value of 2.81 g/cm³, or 2,810 kg/m³. That is about 4% higher than 6061 for the same volume.
Is molten aluminum also 2.70 g/cm³?
No. Melting and additional heating increase volume, so liquid aluminum is less dense than the room-temperature solid. Use alloy- and temperature-specific foundry data for melt calculations.
Why does calculated mass differ from the scale reading?
Common causes include the wrong alloy value, incorrect CAD units, omitted holes, or coating and insert mass. Incomplete machining, trapped liquid, scale error, and porosity can also matter. Check geometry and part state before treating the difference as a material problem.
