lb/in³ to g/cm³

An aircraft structural spec quotes aluminum at 0.0975 lb/in³. The materials engineer verifying it against the datasheet's 2.7 g/cm³ multiplies by 27.679905 — the exact number that converts an inch-cubed pound back into a centimeter-cubed gram. This is the density conversion behind every airframe weight estimate, and it's exact to every digit.

1 lb/in³ = 27.6799047102 g/cm³, and 1 g/cm³ = 0.0361272920001 lb/in³. The conversion is a single fixed factor: multiply lb/in³ by 27.6799047102. Worked: 10 lb/in³ = 276.7990471 g/cm³; 100 lb/in³ = 2,767.99047102 g/cm³.

By EnginStack Editorial Team | Reviewed against NIST, BIPM and primary-source documentation About →
lb/in³
2.69879071 g/cm³
0.0975 lb/in³ = 2.69879071 g/cm³ 0.0975 g/cm³ = 0.00352241 lb/in³

Source: NIST SP 811 and the 1959 yard-and-pound agreement (0.9144 m, 0.45359237 kg). Every decimal place in the factor above is a defined constant, not a measurement.

lb/in³ to g/cm³

An aircraft structural spec quotes aluminum at 0.0975 lb/in³. The materials engineer verifying it against the datasheet's 2.7 g/cm³ multiplies by 27.679905 — the exact number that converts an inch-cubed pound back into a centimeter-cubed gram. This is the density conversion behind every airframe weight estimate, and it's exact to every digit.

g/cm³ = lb/in³ × 27.67990471
1 lb/in³ = 27.67990471 g/cm³ — the 1959 pound (453.59237 g) over the inch cubed
The factor is exact — derived from SI definitions and the 1959 yard/pound agreement.

Worked Examples

Example 1: Verify an aluminum spec of 0.0975 lb/in³

0.0975 × 27.67990471 = 2.70 g/cm³

Example 2: Verify a titanium part at 0.160 lb/in³

0.160 × 27.67990471 = 4.43 g/cm³

Example 3: Verify carbon steel at 0.283 lb/in³

0.283 × 27.67990471 = 7.83 g/cm³

Common lb/in³ to g/cm³ Conversions

lb/in³g/cm³Material / context
1 lb/in³27.68 g/cm³The definitional anchor.
0.0975 lb/in³2.7 g/cm³Aluminum 6061.
0.160 lb/in³4.43 g/cm³Titanium 6Al-4V.
0.283 lb/in³7.83 g/cm³Steel.
0.324 lb/in³8.96 g/cm³Copper.
0.697 lb/in³19.3 g/cm³Gold.

Engineering Context

Density links the mass and volume families on this site — it is their ratio. For the mass numerator, the kg to g and lbs to kg converters carry the same 1959 constants that appear here; for the volume denominator, the liters to mL and cubic feet to cubic meters pages supply the cubed lengths. The density hub collects all ten converters in this family.

This is the direction used for verification rather than for calculation. Because the factor is 27.68, any transcription slip in the source value is amplified by more than an order of magnitude on the way back: a 0.0975 that should have been 0.975 returns 2.70 against 27.0 g/cm³, and 27 is denser than every solid element except osmium, iridium and platinum. Nothing in a stress office can use a number that high, so the reverse conversion acts as a filter. Run it on any incoming imperial density figure before the value reaches a finite-element model.

More: g/cm³ to lb/in³ · lb/ft³ to g/cm³ · g/cm³ to kg/m³ · Density Guide · Density

Related Unit Converters

g/cm³ to lb/in³ lb/ft³ to g/cm³ g/cm³ to kg/m³ Density Conversion Guide Density Converters

Frequently Asked Questions

What are the aerospace density anchors?

Aluminum 6061: 0.0975 lb/in³ = 2.70 g/cm³. Titanium 6Al-4V: 0.160 lb/in³ = 4.43 g/cm³. Steel: 0.283 lb/in³ = 7.83 g/cm³. Inconel 718: 0.296 lb/in³ = 8.19 g/cm³.

Why multiply by 27.679905?

Because that's the exact number of grams per cubic centimeter in one pound per cubic inch — the 1959 pound (453.59237 g) over the inch cubed (16.387064 cm³). Exact to every digit.

Is the 27.68 shortcut good enough?

For estimates, yes — 27.68 is accurate to 0.0004%. For a certified weight audit, use the full 27.679905, because aerospace weight margins are measured in tenths of a percent.