Density of metals chart: iron, aluminium, copper, stainless steel, titanium, brass and gold, specific gravity vs density, and how to calculate weight

Specific gravity tells you how many times heavier something is than the same volume of water.

Among metals it runs from about 0.5 for lithium to about 23 for osmium. Two pieces of the same size can differ in weight by more than forty times.

The key point: specific gravity is almost the same number as density in g/cm³, so you can use it directly to calculate weight.

In this article:

• A quick table of common metals, and a bar chart to compare them
• How specific gravity differs from density, why water at 4 °C is the reference, and unit conversions
• Pure metals, ranked from heaviest and from lightest
• Stainless steel, aluminium alloys, brass and titanium alloy
• Formulas for the weight of plates and round bars, with a table of worked examples

The values were checked against NIST (the US National Institute of Standards and Technology) for the elements. Alloys come from steel, aluminium and copper producers and their industry associations.

In short: what is the density of common metals?

Gold and platinum are about 20, copper about 9, iron and stainless steel about 8, titanium about 4.5 and aluminium about 2.7 g/cm³.

Source (5)

• NIST, "X-Ray Mass Attenuation Coefficients", Table 1 (densities of the elements; no temperature stated, some values nominal)
• Furukawa Electric, "Brass strip" physical properties
• JFE Steel, "Stainless Steel Sheets" catalog (physical properties table; SUS densities are the JIS base mass)
• Nippon Steel, "Titanium" catalog (T001, technical data: comparison of physical properties)
• Japan Aluminium Association, "Material database 3: physical properties" (Tables 1 and 2, 20 °C)

The table runs from heaviest to lightest. Each row is taken from the pure-metal and alloy tables further down.

Stainless steel, brass and aluminium alloys vary with the grade, so they are shown as ranges.

Aluminium weighs about a third as much as iron, and gold about two and a half times as much. Within one metal, the alloy can shift the value by a few percent.

What is specific gravity, in simple terms?

Specific gravity is the weight of a material divided by the weight of the same volume of water.

If iron has a specific gravity of about 7.9, a piece of iron weighs about 7.9 times as much as the same volume of water. Specific gravity has no unit.

Anything with a specific gravity above 1 sinks in water, and anything below 1 floats. Almost all metals sink.

It is often abbreviated SG. Density is the mass per unit volume.

How is specific gravity different from density?

Density is the mass of 1 cm³ (in g/cm³); specific gravity is the ratio to water.

Water has a density of about 1 g/cm³ at 4 °C. That is why density in g/cm³ and specific gravity come out as almost the same number.

They differ only beyond the fourth decimal place. For weight calculations you can treat them as the same.

Why is water at 4 °C the reference?

Water is densest at about 4 °C, so that is the temperature used as the reference.

Source: NIST Chemistry WebBook, "Thermophysical Properties of Fluid Systems" (water, 0.101325 MPa)

Water gets slightly less dense as it warms. At 20 °C it is about 0.2% lighter than at 4 °C.

Most metal tables are based on densities measured at ordinary temperatures. The difference can be ignored in everyday calculations.

How do you convert density units?

Multiply a value in g/cm³ by 1,000 to get kg/m³. Mg/m³, t/m³ and kg/L give the same number as g/cm³.

Source: Unit definitions (1 m³ = 1,000,000 cm³, 1 L = 1,000 cm³, 1 cm³ = 1,000 mm³)

One cubic metre is 1,000,000 cm³ and one kilogram is 1,000 g, which gives the factor of 1,000.

CAD software often asks for g/mm³ or kg/mm³. Pick the wrong unit and the weight is off by a factor of 1,000.

The "base mass" in kg/(mm·m²) in steel sheet catalogs is the weight of a 1 mm plate of 1 m². It is the same number as the density in g/cm³.

What is the density of pure metals?

Osmium and iridium are the densest at about 22.5 g/cm³; lithium is the lightest at about 0.5.

Source: NIST, "X-Ray Mass Attenuation Coefficients", Table 1 (densities of the elements; no temperature stated, some values nominal)

The values come from NIST's table of the elements. The table gives no temperature, and some values are marked as nominal.

Pure-metal values differ slightly from product values for alloys and commercial metals. Titanium is 4.54 in this table and 4.51 in a producer's data.

Pure iron is 7.874, but steel weights are calculated with 7.85. Use the alloy table further down for products.

Which metals are heaviest and lightest?

The heaviest are osmium, iridium and platinum; the lightest are lithium, potassium and sodium.

What is the order of the heaviest metals?

Source: NIST, "X-Ray Mass Attenuation Coefficients", Table 1 (densities of the elements; no temperature stated, some values nominal)

Osmium and iridium are less than 1% apart. Some sources put them the other way round.

Platinum, gold and tungsten are all about 19 to 21. Size for size, they weigh about 2.5 to 2.7 times as much as iron.

Mercury is liquid at room temperature, yet it is heavier than lead or silver.

What is the order of the lightest metals?

Source: NIST, "X-Ray Mass Attenuation Coefficients", Table 1 (densities of the elements; no temperature stated, some values nominal)

Lithium, potassium and sodium have a specific gravity below 1, so they are lighter than water.

They react violently with water, though, and are not used as everyday materials.

The light metals that are used as materials are magnesium, aluminium and titanium.

A metal with a specific gravity below 1 floats on water. Only the top three in the table do.

Which metal has a density closest to gold?

Tungsten is closest to gold: gold is 19.32 and tungsten 19.30.

They are only about 0.1% apart. Weight and size alone can hardly tell gold from tungsten.

The next closest are platinum (about 21.5) and tantalum (about 16.7). Both differ from gold by more than 2.

Specific gravity is one clue for telling metals apart. It cannot always decide on its own whether gold is genuine.

Why do alloys have a range of densities?

An alloy's density depends on which elements are added and how much, so "stainless steel" or "aluminium" has no single value.

Adding heavy elements makes it heavier; adding light ones makes it lighter. For example, 7075, which contains zinc, is heavier than pure aluminium.

That is why alloy values are given grade by grade. The tables here also list one grade per row.

What is the density of stainless steel?

Stainless steel is about 7.7 to 8.0; 304 is 7.93 and 430 is 7.70.

Source: JFE Steel, "Stainless Steel Sheets" catalog (physical properties table; SUS densities are the JIS base mass)

These are catalog values from a steel producer and match the "base mass" set in JIS (Japanese Industrial Standards).

The nickel grades 304 and 316 are slightly heavier than carbon steel. Grades 430 and 410 are slightly lighter.

Grade 304 is only about 1% heavier than SS400 steel. You can treat them as the same weight.

Is the density of iron 7.85 or 7.87?

Steel weights are calculated with 7.85; pure iron is 7.874.

Steel is iron with carbon and other elements added. Steel sheet catalogs give 7.85 for mild steel.

In kg/m³ steel is 7,850. If someone says "iron is 7850", they mean kg/m³.

What is the density of aluminium?

Aluminium is about 2.7; alloys range from about 2.66 to 2.8.

Source: Japan Aluminium Association, "Material database 3: physical properties" (Tables 1 and 2, 20 °C) / Japan Aluminium Association, "Aluminium in building: features" (Table 2, standard physical properties)

The Japan Aluminium Association says 2.7 is normally used whatever the alloy. Use the table only when small differences matter.

The magnesium-rich 5182 and 5052 are lighter. The copper or zinc alloys 2024 and 7075 are heavier.

What is the density of copper and brass?

Copper is about 8.9 to 9.0; brass contains zinc and is about 8.5.

Source: Japan Copper Development Association, "Physical and mechanical properties of copper" (from the Copper Products Data Book, 20 °C) / Furukawa Electric, "Brass strip" physical properties

Brass is an alloy of copper and zinc. Zinc is lighter than copper, so the more zinc, the lower the density.

Brass is about 5% lighter than copper. They may look alike, but a copper piece of the same size is heavier.

Values for free-cutting brass (C3604) and C2801 could not be confirmed in primary sources, so they are not in the table.

What is the density of titanium?

Titanium is about 4.5; the Ti-6Al-4V alloy is 4.43.

Source: Nippon Steel, "Titanium" catalog (T001, technical data: comparison of physical properties)

Titanium weighs about 60% as much as iron and about 1.7 times as much as aluminium. It balances lightness and strength well.

For hardness, see the Mohs hardness chart.

How do you calculate the weight of metal?

Weight is volume times specific gravity; with cm³ and g/cm³ the answer comes out in grams.

The plate formula is the base-mass idea: a 1 mm plate of 1 m² weighs the same number of kilograms as its specific gravity.

The 0.785 in the bar formula is π divided by 4, used to get a circle's area from its diameter.

What are some worked weight examples?

Here are a plate, a 3×6 ft sheet and a round bar in six common materials.

Source (5)

• Japan Aluminium Association, "Aluminium in building: features" (Table 2, standard physical properties)
• Nippon Steel, "Titanium" catalog (T001, technical data: comparison of physical properties)
• JFE Steel, "Stainless Steel Sheets" catalog (physical properties table; SUS densities are the JIS base mass)
• Furukawa Electric, "Brass strip" physical properties
• Japan Copper Development Association, "Physical and mechanical properties of copper" (from the Copper Products Data Book, 20 °C)

The 3×6 sheet is 3 shaku by 6 shaku (914 × 1,829 mm), a common Japanese sheet size. The table gives its weight at 1 mm thick.

Double the thickness and the weight doubles. For the same size, an aluminium plate weighs about a third as much as a steel one.

How do you calculate the weight of a plate?

Plate weight in kg is thickness (mm) × width (m) × length (m) × specific gravity.

Take an SS400 plate 3 mm thick, 1 m wide and 2 m long: 3 × 1 × 2 × 7.85 gives about 47 kg.

The formula is the same for any metal once the units match. Just swap in the specific gravity from the table.

How do you calculate the weight of a round bar?

Round-bar weight in kg is diameter (cm) squared × 0.785 × length (m) × specific gravity ÷ 10.

A 20 mm bar is 2 cm across. For grade 304 stainless, 1 m long: 2 × 2 × 0.785 × 1 × 7.93 ÷ 10 gives about 2.5 kg.

A bar's weight goes with the square of its diameter, so doubling the diameter makes it four times as heavy.

How is specific gravity measured?

Weigh the piece in air and in water: specific gravity is the weight in air ÷ (weight in air − weight in water).

Under water an object loses the weight of the water it pushes aside. That loss is the weight of the same volume of water.

If a piece weighs 100 g in air and 90 g in water, its specific gravity is 100 ÷ 10, or 10.

A hidden cavity makes the result too low. Plating, where only the surface is another metal, is also hard to detect this way.

Common questions about the density of metals

What is the density of iron in kg/m³?

Steel calculations use 7,850 kg/m³; pure iron is 7,874 kg/m³.

Multiply the g/cm³ value by 1,000 to get kg/m³.

How much lighter is aluminium than iron?

Aluminium weighs about a third as much as SS400 steel.

Pure aluminium at 2.699 divided by steel at 7.85 gives about 0.34. Aluminium alloys are about the same.

Is stainless steel heavier than iron?

Grade 304 is about 1% heavier than SS400 steel, and grade 430 about 2% lighter.

Both differences are small enough to treat them as the same weight in calculations.

Is titanium heavier than aluminium?

Yes. Titanium is about 1.7 times as heavy as aluminium.

Compared with iron, though, it weighs only about 60% as much. It is light for its strength.

Which metal has the highest density?

In the NIST table, osmium is the densest metal at 22.57.

Iridium, in second place, is less than 1% behind. Some sources rank them the other way round.

Can I compare how well metals conduct heat?

Yes, see the thermal conductivity chart.

It lists pure metals and alloys in the same kind of table. For the temperatures at which metals melt, see the melting points of metals chart.

Sources

• X-Ray Mass Attenuation Coefficients, Table 1 (NIST, densities of the elements)
• Stainless Steel Sheets catalog (JFE Steel, physical properties table)
• Stainless Steel Cold Rolled Sheets catalog S008 (Nippon Steel, base mass in the mass table)
• Material database 3: physical properties (Japan Aluminium Association)
• Aluminium in building: features, Table 2 (Japan Aluminium Association)
• Physical and mechanical properties of copper (Japan Copper Development Association)
• Brass strip (Furukawa Electric)
• Titanium catalog T001 (Nippon Steel, comparison of physical properties)
• Thermophysical Properties of Fluid Systems (NIST Chemistry WebBook, density of water)