Rock Density Calculator

Use this rock density calculator to quickly find the density of a rock sample from its mass and volume. Enter the rock’s mass in grams and its volume in cubic centimeters (cm³) to get density in grams per cubic centimeter (g/cm³), then compare your result with typical values for common rock types.

Why measure rock density?

Density is a core physical property in geology and engineering. It describes how much mass is packed into a given volume, and it can reveal a lot about a rock’s composition and history.

• Geology and petrology: Denser rocks usually contain more iron- and magnesium-rich minerals, while lower-density rocks tend to be rich in silica or have high porosity.
• Mining and ore evaluation: Ore bodies containing metals such as lead, copper, or iron often have significantly higher densities than surrounding host rocks.
• Civil and structural engineering: Knowing the density of rock used as aggregate or foundation material helps estimate loads and design safe structures.
• Archaeology and conservation: Density measurements can support material identification for artifacts and building stones.

By combining simple mass and volume measurements, this calculator provides an approximate density you can use for classification, comparison, or engineering estimates.

Density formula

The basic relationship between mass, volume, and density is:

Density = Mass ÷ Volume

Mathematically, this is written as:

where:

• ρ (rho) is density
• m is mass
• V is volume

On this page, enter:

• Mass in grams (g)
• Volume in cubic centimeters (cm³)

The calculator then returns density in grams per cubic centimeter (g/cm³). If you need density in kilograms per cubic meter (kg/m³), you can multiply the result by 1,000, because:

1 g/cm³ = 1,000 kg/m³

How to measure mass and volume

Mass

• Use a balance or scale that reads in grams.
• Make sure the scale is zeroed (tared) before placing the rock on it.
• Record the mass in grams and enter that value into the calculator.

Volume of irregular rocks

Most rocks are irregular in shape, so volume is usually measured by water displacement:

1. Fill a graduated cylinder, beaker, or other container with enough water to completely submerge the rock.
2. Record the initial water level (in mL or cm³).
3. Carefully place the rock in the water, avoiding splashing.
4. Record the final water level.
5. Compute the volume of the rock as: final level − initial level.

Because 1 milliliter (mL) of water occupies 1 cubic centimeter (cm³), the change in water level in mL is numerically equal to the rock’s volume in cm³.

Unit tips and conversions

• If your mass is in kilograms (kg), multiply by 1,000 to convert to grams. Example: 0.75 kg = 750 g.
• If your volume is in liters (L), multiply by 1,000 to convert to cm³. Example: 0.4 L = 400 cm³.
• Always convert to grams and cm³ before using the calculator so your density value is correct.

Interpreting your results

Once you click the button, the calculator will display the density of your sample in g/cm³. You can then compare this value with typical density ranges to get a rough idea of the rock type or composition.

Use these ranges as broad guidelines only. Many factors, including porosity, mineral substitutions, and inclusions, can shift a sample’s density above or below the typical range.

Worked example with this calculator

Suppose you collect a rock sample and measure:

• Mass = 500 g
• Volume = 200 cm³

Using the density formula:

Density = Mass ÷ Volume = 500 g ÷ 200 cm³ = 2.5 g/cm³

A density of about 2.5 g/cm³ is consistent with some sandstones, limestones, or lower-density granitic rocks. It is lighter than typical basalt and far lighter than metallic ores such as hematite or galena. If you know the rock’s texture and mineralogy from visual inspection or thin-section analysis, combining that information with this density estimate can help refine the classification.

Assumptions and limitations

• Consistent units: The calculator assumes mass in grams and volume in cm³. Entering mixed or incorrect units will produce incorrect densities.
• Bulk density, not grain density: The result is a bulk density that includes pore spaces, fractures, and any fluid in those pores. It is different from grain density measured on crushed or dried material.
• Dry or controlled moisture: For most comparisons, samples are assumed to be dry or at a known moisture condition. Wet samples, especially porous ones, can appear artificially dense because water adds mass without greatly changing measured volume.
• Water displacement accuracy: The volume method assumes all displaced water is due to the rock’s external volume. Trapped air bubbles, splashing, or water absorption can introduce error.
• Field vs. lab conditions: Field measurements with improvised containers or rough scales are typically less precise than laboratory measurements. Treat field results as approximate.
• Heterogeneous samples: Many rocks are mixtures of minerals and voids. A single density value may not fully describe variations within the sample or between different parts of the same outcrop.

Because of these limitations, use this calculator as a helpful estimation tool rather than a substitute for full laboratory testing when high accuracy is required for design, safety, or economic decisions.

Related measurements and tools

For more detailed material characterization, you might also use tools such as bulk density calculators for soils and aggregates, porosity calculators, or mass–volume unit converters. Combining density with other properties, like porosity and water content, gives a more complete picture of how a rock or aggregate will behave in engineering and geological settings.