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.
Common lb/in³ to g/cm³ Conversions
| lb/in³ | g/cm³ | Material / context |
|---|---|---|
| 1 lb/in³ | 27.68 g/cm³ | The definitional anchor. |
| 0.0975 lb/in³ | 2.7 g/cm³ | Aluminum 6061. |
| 0.160 lb/in³ | 4.43 g/cm³ | Titanium 6Al-4V. |
| 0.283 lb/in³ | 7.83 g/cm³ | Steel. |
| 0.324 lb/in³ | 8.96 g/cm³ | Copper. |
| 0.697 lb/in³ | 19.3 g/cm³ | Gold. |
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.
More: G Cm3 To Lb In3 · Lb Ft3 To G Cm3 · G Cm3 To Kg M3 · Density
Related Unit 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.