lb/ft³ to kg/m³

A US drawing says the fill material weighs 110 lb/ft³. The metric counterpart asks for kg/m³: 1,762. The conversion factor, 16.018463, is the exact number that carries a 1959 pound over a 1959 foot cubed — and it's the same number whether you're shipping a soil spec to a European lab or checking concrete against an international standard.

1 lb/ft³ = 16.018463374 kg/m³, and 1 kg/m³ = 0.0624279605761 lb/ft³. The conversion is a single fixed factor: multiply lb/ft³ by 16.018463374. Worked: 10 lb/ft³ = 160.18463374 kg/m³; 100 lb/ft³ = 1,601.8463374 kg/m³.

By EnginStack Editorial Team | Reviewed against NIST, BIPM and primary-source documentation About →
lb/ft³
999.55211454 kg/m³
62.4 lb/ft³ = 999.55211454 kg/m³ 62.4 kg/m³ = 3.89550474 lb/ft³

Authority: NIST SP 811 (SI usage guide) and the 1959 International Yard and Pound Agreement. The coefficient above is a defined value — it does not come from measurement and carries no uncertainty.

lb/ft³ to kg/m³

A US drawing says the fill material weighs 110 lb/ft³. The metric counterpart asks for kg/m³: 1,762. The conversion factor, 16.018463, is the exact number that carries a 1959 pound over a 1959 foot cubed — and it's the same number whether you're shipping a soil spec to a European lab or checking concrete against an international standard.

kg/m³ = lb/ft³ × 16.01846337
1 lb/ft³ = 16.01846337 kg/m³ — the 1959 pound over the 1959 foot, cubed
The factor is exact — derived from SI definitions and the 1959 yard/pound agreement.

Worked Examples

Example 1: Convert compacted soil at 110 lb/ft³

110 × 16.01846337 = 1,762 kg/m³

Example 2: Convert normal-weight concrete at 150 lb/ft³

150 × 16.01846337 = 2,403 kg/m³

Example 3: Convert water at 62.4 lb/ft³

62.4 × 16.01846337 = 999.6 kg/m³

Common lb/ft³ to kg/m³ Conversions

lb/ft³kg/m³Material / context
1 lb/ft³16.02 kg/m³The definitional anchor.
37.5 lb/ft³600 kg/m³Dry pine wood.
62.4 lb/ft³1,000 kg/m³Water — the construction anchor.
110 lb/ft³1,762 kg/m³Typical compacted soil.
150 lb/ft³2,403 kg/m³Normal-weight concrete.
490 lb/ft³7,849 kg/m³Carbon steel.

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.

Sixteen point zero two is the single most used mixed-unit constant in civil engineering, and it appears everywhere a metric design meets a US batch plant: soil compaction specs, concrete unit weight, aggregate stockpiles, structural dead loads. The conversion itself is exact, but the inputs usually are not. US earthwork specifications are quoted to two or three significant figures (110, 120, 125 lb/ft³) precisely because compaction is variable, so a converted value quoted to four digits, 1,762 kg/m³, is asserting a precision the original never had. Keep the factor exact and cut the answer to the input.

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

Related Unit Converters

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

Frequently Asked Questions

How do I estimate kg/m³ from lb/ft³ quickly?

Multiply by 16. For a quick estimate, 150 lb/ft³ × 16 = 2,400 kg/m³ — the concrete number everyone remembers. The exact factor is 16.018463, so the shortcut is accurate to about 0.1%.

Why does US construction use lb/ft³?

Because the US building codes and test standards were written in customary units, and the density values became memorable: 62.4 for water, 150 for concrete, 110 for soil. The industry stays bilingual and converts.

Is 62.4 lb/ft³ water or 62.428?

62.4 is the shorthand; the exact value for water at 4 °C is 62.427961 lb/ft³. The 0.04% difference is irrelevant for concrete mix design but matters in hydrology and naval architecture.