lb/ft³ to kg/m³ Converter
1 lb/ft³ = 16.01846337 kg/m³ exactly, derived from the exact definitions: 1 lb = 0.45359237 kg and 1 ft = 0.3048 m (so 1 ft³ = 0.02831685 m³). Therefore 1 lb/ft³ = 0.45359237 /...
Formula
Source: NIST SP 811, ISO 80000-4 | Last reviewed: June 27, 2026
Examples
1 lb/ft³
= 16.02 kg/m³
1 lb/ft³ = 16.02 kg/m³
62.43 lb/ft³
= 1000 kg/m³
Density of water at 4°C (62.43 lb/ft³ → 1,000 kg/m³)
0.0765 lb/ft³
= 1.225 kg/m³
Standard air density at sea level
490 lb/ft³
= 7850 kg/m³
Density of carbon steel
150 lb/ft³
= 2403 kg/m³
Density of normal-weight concrete
Quick Reference Table
| Material | lb/ft³ | kg/m³ |
|---|---|---|
| Air (sea level, 70°F) | 0.075 | 1.2 |
| Water (4°C) | 62.43 | 1000 |
| Water (70°F / 21°C) | 62.3 | 998 |
| Gasoline | 45-48.7 | 720-780 |
| Diesel | 51.8-54.3 | 830-870 |
| Crude oil (light) | 50-55 | 800-880 |
| Concrete | 150 | 2400 |
| Carbon steel | 490 | 7850 |
| Aluminum | 168.5 | 2700 |
| Mercury | 846 | 13560 |
Where is this used?
Therefore 1 lb/ft³ = 0.45359237 / 0.0283168466 = 16.01846337 kg/m³.
This conversion is the primary bridge from US customary density data to SI, used whenever US-published material properties, equipment specifications, or engineering calculations must be integrated into international documentation or software.
The factor 16.0185 is worth memorizing alongside other key US-to-SI conversion factors.
Water at its maximum density (4°C) is 62.428 lb/ft³ = 1,000 kg/m³, this 62.4 ↔ 1,000 equivalence is the most useful density sanity check.
A US pump curve that specifies a pump's NPSH requirement based on water at 62.4 lb/ft³ must be corrected when pumping a fluid at, say, 55 lb/ft³ (a light hydrocarbon).
The NPSH available in feet of liquid is inversely proportional to density: the same absolute pressure (in psi) provides more feet of head for a lighter fluid.
Converting the fluid density from lb/ft³ to kg/m³ (55 × 16.0185 = 881 kg/m³) connects the US pump specification to the European fluid property database.
In US HVAC duct design, standard air density is 0.075 lb/ft³ at 70°F and sea level, converting to SI: 0.075 × 16.0185 = 1.20 kg/m³.
This value is used in European fan laws and duct sizing charts (which use kg/m³ for air density).
At Denver's altitude (5,280 ft, atmospheric pressure 12.2 psia), the air density drops to about 0.062 lb/ft³ (0.99 kg/m³), and the fan mass flow capacity is reduced proportionally, this altitude correction requires the density conversion to be accurate.
In US mining and mineral processing, slurry density is often specified in lb/ft³ (or as specific gravity, SG), a copper concentrate slurry at 65% solids by weight with an SG of 2.0 has a density of 2.0 × 62.4 = 124.8 lb/ft³ = 124.8 × 16.0185 = 1,999 kg/m³.
The US pump sizing calculation (WHP = Q × H × SG / 3960, where Q in GPM, H in feet) uses SG, which is dimensionless and unit-independent, so the lb/ft³ value converts seamlessly to kg/m³ for the European pipe friction calculation without affecting the SG-based pump power result.
Real-World Usage Scenarios
US drilling fluid specification for international rig
A US drilling contractor operating in the Norwegian North Sea uses drilling fluids (muds) specified by an American Petroleum Institute (API) standard, with densities in lb/ft³ (lb/USg for mud weight, a related unit). The Norwegian drilling engineer reviews the API spec and converts to kg/m³ for integration with the European drilling program: a 12 lb/gal mud (typical for intermediate casing strings) = 12 × 119.83 (lb/gal to kg/m³) = 1,438 kg/m³ = 14.1 kN/m³. The conversion is required for the European mud engineering calculations (equivalent circulating density, ECD, in kg/m³; hydrostatic pressure calculations in bar). A 1% error in the density conversion (e.g., using 1,420 instead of 1,438 kg/m³) translates to about 0.7% error in the hydrostatic pressure at the casing shoe, for a 3,000 m deep well, this is about 2 bar of error, potentially enough to cause a kick (formation fluid influx) if the mud weight is underestimated, or a lost circulation event (formation fracture) if overestimated. The lb/ft³ to kg/m³ conversion (× 16.0185) is the foundation of the international drilling program compatibility.
Industry Standards Referenced
Frequently Asked Questions
Is the conversion factor 16.0185 exact?
Yes, to the extent that the pound and the foot are exact SI definitions: 1 lb = 0.45359237 kg exactly, 1 ft = 0.3048 m exactly. Therefore 1 lb/ft³ = 0.45359237 / (0.3048³) = 0.45359237 / 0.028316846592 = 16.01846337 kg/m³ exactly. The commonly used 16.0185 or 16.02 has 4-5 significant figures and is sufficient for all industrial density calculations.
What does this converter do?
This converter performs the unit conversion at standard conditions using the exact conversion factor. The result is displayed with appropriate precision for engineering use.
How accurate is the conversion?
The conversion factor used is exact or to four significant figures depending on the units. For most engineering calculations, the precision is more than sufficient. For precision work, consult the relevant NIST or ISO standards referenced on this page.
Reviewed for accuracy
Verified against NIST standard unit conversion tables · Last reviewed: June 27, 2026
All calculations are for reference only. Always verify with manufacturer data and a qualified engineer for critical applications. Learn about our editorial process.