lb/ft³ to g/cm³
The US shop floor thinks in pounds per cubic foot: steel is 490, aluminum is 169. The international materials datasheet speaks g/cm³: steel is 7.85, aluminum is 2.70. The conversion is one division by 62.427961 — the density of water in US customary units.
g/cm³ = lb/ft³ × 0.01601846327
1 lb/ft³ = 0.01601846327 g/cm³ — the reciprocal of 62.427961
The factor is exact — derived from SI definitions and the 1959 yard/pound agreement.
Common lb/ft³ to g/cm³ Conversions
| lb/ft³ | g/cm³ | Material / context |
|---|---|---|
| 1 lb/ft³ | 0.0160 g/cm³ | The definitional anchor. |
| 62.4 lb/ft³ | 1 g/cm³ | Water. |
| 110 lb/ft³ | 1.76 g/cm³ | Compacted soil. |
| 168.6 lb/ft³ | 2.7 g/cm³ | Aluminum. |
| 490 lb/ft³ | 7.85 g/cm³ | Carbon steel. |
| 559 lb/ft³ | 8.96 g/cm³ | Copper. |
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 Ft3 · Lb Ft3 To Kg M3 · G Cm3 To Kg M3 · Density
Related Unit Converters
Frequently Asked Questions
Is 490 lb/ft³ steel or 489?
Structural steel is commonly specified at 490 lb/ft³ (about 7.85 g/cm³). The exact value varies slightly with alloy — carbon steel is about 7.83-7.87 g/cm³. For certified work use the alloy's exact value; for estimates, 490 is the industry standard.
How do I convert lb/ft³ to g/cm³ quickly?
Divide by 62.4: 150 ÷ 62.4 = 2.40 g/cm³ (concrete); 490 ÷ 62.4 = 7.85 g/cm³ (steel). The exact factor is 62.427961, making the shortcut accurate to 0.05%.
Why does the same material have two memorable numbers?
Each industry picked the unit that made its numbers round. Metric materials engineering got 2.7 for aluminum and 7.85 for steel in g/cm³. US construction got 169 and 490 in lb/ft³. The 62.4 bridge is exact.