Density Converter

Convert density between g/cm³, kg/m³, lb/in³, and lb/ft³ for material specifications.

Converter

Common Metal Densities

Material g/cm³ kg/m³ lb/in³

How to Use

  1. 1
    Enter the Density Value and Source Unit

    Input the density value and select the source unit: g/cm³, kg/m³, lb/in³, or lb/ft³.

  2. 2
    Read Equivalents Across All Common Units

    All equivalent values are displayed simultaneously; the tool also shows the specific gravity (relative to water at 4°C) as a dimensionless reference.

  3. 3
    Use the Alloy Density Reference Table

    Browse the reference table of densities for common engineering alloy families to contextualize your converted value within the spectrum of engineering metals.

About

Density conversion arises constantly in materials engineering workflows that span unit systems. Weight calculations, specific strength comparisons, shipping cost estimation, and Archimedes method density measurements all require accurate conversions between g/cm³, kg/m³, and lb/in³. The AlloyFYI Density Converter handles these conversions instantly while providing a contextual reference table of densities for the major engineering alloy families, helping engineers sanity-check measured or calculated values against expected ranges for the material class.

The tool is particularly useful when evaluating material substitution: comparing the density of candidate materials directly in lb/in³ (as specified in many American aerospace drawings) alongside the equivalent kg/m³ value (from European or Asian supplier datasheets) eliminates the manual conversion step and the transcription errors it introduces. The linked specific gravity display also supports Archimedes measurement calculations in incoming material inspection workflows.

FAQ

What is the difference between density and specific gravity?
Density is mass per unit volume, expressed in dimensional units such as g/cm³ or kg/m³. Specific gravity is the dimensionless ratio of a material's density to the density of a reference material — for solids, the reference is water at 4°C (density = 1.000 g/cm³ = 1,000 kg/m³). Because the reference density of water is exactly 1.000 g/cm³ in CGS units, specific gravity numerically equals density in g/cm³, which is why the terms are often used interchangeably. The distinction matters only when absolute precision is needed or when a non-water reference is used (e.g., specific gravity relative to air in gas density measurement).
How do I convert from kg/m³ to lb/in³?
1 kg/m³ = 3.6127×10⁻⁵ lb/in³. Conversely, 1 lb/in³ = 27,679.9 kg/m³. For practical reference: steel at 7,850 kg/m³ = 0.2836 lb/in³; aluminum at 2,700 kg/m³ = 0.0975 lb/in³; titanium at 4,430 kg/m³ = 0.1600 lb/in³. American engineering documents for aerospace and automotive applications commonly express density in lb/in³, while SI-based documents use kg/m³, so this conversion arises frequently in international engineering work.
What density value should I use for a steel weldment (base metal plus weld)?
For a weldment consisting of carbon steel base metal and a compatible filler metal, the difference in density between most carbon steel filler metals and the base metal is less than 0.5%, so using 7,850 kg/m³ for the entire assembly is accurate for weight calculations. For stainless steel weldments, both base and filler metal densities are typically in the range 7,900–7,970 kg/m³. Weld metal penetration profiles and reinforcement volumes add 5–10% excess material to the theoretical joint volume, which should be included in weight estimates for precision applications.
How does porosity affect the effective density of castings?
Porosity in castings reduces the bulk density below the theoretical value. Radiographic and CT inspection classifies porosity by type (shrinkage, gas, microporosity) and volume fraction. Shrinkage porosity in aluminum alloy die castings can reduce density by 1–3%, while in low-pressure sand castings up to 5% reduction is possible in poorly gated sections. The effective density of a porous casting is: ρ_eff = ρ_theoretical × (1 − Vf_porosity), where Vf is the volume fraction of pores. For structural applications, X-ray or CT measurement of porosity is used to verify that density meets acceptance criteria.
Why do different alloys of the same base metal have different densities?
Alloying elements have their own atomic masses and crystal packing efficiencies that alter the average density of the base metal. Adding lighter elements like aluminum or titanium reduces density, while heavier elements like tungsten or molybdenum increase it. The crystal structure may also change with composition — for example, austenitic stainless steels (FCC structure) are slightly denser than ferritic grades (BCC structure) of similar composition. Heat treatment and cold working can further affect density by introducing lattice defects or phase transformations.
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