Pounds per cubic foot to Pounds per US gallon Calculator

Direct answer

Multiply the entered pounds per cubic foot value by 0.133680555556555 to express it in pounds per us gallon (lb/US gal). This converts pound per cubic foot (lb/ft³) to pound per US gallon (lb/US gal) within the documented density family.

Variables and formula

• Pounds per cubic foot (lb/ft³): the source value measured in pound per cubic foot.
• Pounds per US gallon (lb/US gal): the same quantity expressed in pound per US gallon.
• Conversion factor: 0.133680555556555 pounds per us gallon per pound per cubic foot.

Pounds per US gallon = Pounds per cubic foot × 0.133680555556555

The generator emits numeric factors with at most 15 significant digits. Calculator results keep up to 10 significant digits for display; this formatting does not increase the precision of the measurement.

Unit definitions and named variants

Source unit: pound per cubic foot (lb/ft³). This unit uses one avoirdupois pound per cubic international foot; its exact-reference conversion begins 16.018463373960139… kg/m³. Named variant used: Avoirdupois pound per cubic international foot; not pound-force or survey-foot volume. Reference: National Institute of Standards and Technology: NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically; National Institute of Standards and Technology: NIST Handbook 44 (2026), Appendix C: General Tables of Units of Measurement.

Target unit: pound per US gallon (lb/US gal). This unit uses one avoirdupois pound per U.S. liquid gallon, where 1 U.S. gal = 231 in³ = 0.003785411784 m³ exactly. Named variant used: U.S. liquid gallon only; not the British Imperial gallon. Reference: National Institute of Standards and Technology: NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically; National Institute of Standards and Technology: NIST Handbook 44 (2026), Appendix C: General Tables of Units of Measurement.

The lb/ft³-to-lb/US gal direction remains inside the density quantity; it changes the unit label and numerical scale, not the kind of quantity being measured.

Relationship and precision

This route uses at least one deliberately preserved rounded factor. Treat the displayed factor as an approximation at the precision documented below.

• lb/ft³ relationship: The preserved application factor is a rounded decimal of the exact value derived from 0.45359237 kg and (0.3048 m)³.
• lb/US gal relationship: The preserved application factor is truncated relative to the exact-reference quotient 119.8264273168966… kg/m³; this discrepancy is documented rather than silently changing the generator factor.

To audit the factor through the family base unit, divide the raw dataset factors 16.01846337396 by 119.826427316. The generator emits that quotient once at 15 significant digits as the canonical direct factor 0.133680555556555; runtime calculations do not divide the already-emitted base factors again.

Reproducible example

For 10 pounds per cubic foot, 10 × 0.133680555556555 = 1.33680555556555 pounds per us gallon. Repeating the same multiplication with the stated factor reproduces the displayed conversion before interface rounding.

Directional scale check

Because one pound per cubic foot contains 0.133680555556555 pounds per us gallon, the target number is smaller than the source number for every positive input. Zero maps to zero, while negative inputs are rejected because this family models non-negative magnitudes.

Interpretation

Read the result as pounds per us gallon, not pounds per cubic foot. A value entered as lb/ft³ leaves the calculator labelled lb/US gal; this directional distinction matters even when the two units describe the same density quantity.

Assumptions and limitations

• Only non-negative mass-density magnitudes are accepted by this family.
• This family covers mass density only; it does not convert relative density, specific gravity, number density, or weight density.
• Pound per US gallon means avoirdupois pounds per U.S. liquid gallon of exactly 231 cubic inches, not an Imperial gallon.

Common mistakes

• Do not substitute a legacy U.S. survey-foot volume.
• An Imperial gallon is larger and produces a different density factor.

Continue within the Density family

See the Density conversion hub for its five-unit reference table and all 20 directed routes.

• Reverse the direction: Pounds per US gallon to Pounds per cubic foot
• Compare another density route: Pounds per cubic foot to Kilograms per cubic meter
• Compare another density route: Pounds per cubic foot to Grams per cubic centimeter
• Compare another density route: Pounds per cubic foot to Kilograms per liter
• Compare another density route: Pounds per US gallon to Kilograms per cubic meter

Assumptions

• The entered value uses pounds per cubic foot exactly as labelled.
• Only non-negative mass-density magnitudes are accepted by this family.
• Rounding and measurement uncertainty remain the user's responsibility.

Sources and methodology

CalcMotive publishes the formula and assumptions so you can decide whether the estimate fits your use case. See our methodology standards.

• NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically; National Institute of Standards and Technology; accessed Aug 7, 2026
• NIST Handbook 44 (2026), Appendix C: General Tables of Units of Measurement; National Institute of Standards and Technology; accessed Aug 7, 2026