Mass per volume density.
Pounds per Cubic foot to Grain per Cubic inches Converter — lb/ft3 to gr/in3
Convert Pound per Cubic foot (lb/ft3) to Grain per Cubic inch (gr/in3) using the exact conversion factor (1 pound per cubic foot = 4.050925926 grain per cubic inch). See the formula, worked examples, conversion table, and common uses.
Pounds per Cubic foot to Grain per Cubic inches converter
Converter
Density Converter
Convert thousands of mass-per-volume density combinations for science, engineering, agriculture, and fluids.
Context values
Some unit families need one extra value for a physically accurate result.
Mass per volume density.
Result = input x 16.01846337 / 3.954272101.
Density uses kilograms per cubic meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Pounds per Cubic foot to Grain per Cubic inches
Pound per Cubic foot and Grain per Cubic inch both measure density — mass per unit volume — a property used to identify materials, check manufacturing quality, and predict whether something floats or sinks. As a fixed reference point, water has a density of exactly 1000 kg/m³ (1 g/cm³, 1 g/mL) at its temperature of maximum density, which is why many density figures in science and engineering are quoted relative to water. Pound per Cubic foot is most often used for us construction material density specs (concrete, soil, lumber, insulation).
Formula
grain per cubic inches = pounds per cubic foot × 4.05092592593
This factor comes from each unit's defined relationship to the category's base unit: 1 pound per cubic foot equals 16.018463374 base units, and 1 grain per cubic inch equals 3.95427210146 base units, so dividing one by the other gives the direct pound per cubic foot-to-grain per cubic inch factor of 4.05092592593.
Simple example
1 lb/ft3 × 4.050925926 = 4.050925926 gr/in3
1 pound per cubic foot = 4.050925926 grain per cubic inches.
Real-world example
1,000 lb/ft3 × 4.050925926 = 4,050.925926 gr/in3
1,000 pounds per cubic foot = 4,050.925926 grain per cubic inches.
Conversion table
| Pound per Cubic foot (lb/ft3) | Grain per Cubic inch (gr/in3) |
|---|---|
| 0.1 lb/ft3 | 0.4050925926 gr/in3 |
| 1 lb/ft3 | 4.050925926 gr/in3 |
| 10 lb/ft3 | 40.50925926 gr/in3 |
| 100 lb/ft3 | 405.0925926 gr/in3 |
| 1,000 lb/ft3 | 4,050.925926 gr/in3 |
| 10,000 lb/ft3 | 40,509.25926 gr/in3 |
Reverse conversion: Grain per Cubic inch to Pound per Cubic foot
4.050925926 gr/in3 × 0.2468571429 = 1 lb/ft3
4.050925926 grain per cubic inches = 1 pounds per cubic foot.
pounds per cubic foot = grain per cubic inches × 0.246857142857
For a page dedicated to this direction, see Grain per Cubic inch to Pound per Cubic foot.
Understanding the Pound per Cubic foot
Pound per Cubic foot (lb/ft3) measures density. The US customary unit for expressing density, commonly used in construction and engineering material specifications. It is classified as a US customary density unit.
Where it's used: United States (construction, engineering, materials specifications)
Uses of the Pound per Cubic foot today
- US construction material density specs (concrete, soil, lumber, insulation)
- US engineering material property tables
- Bulk material handling and shipping weight estimates
Understanding the Grain per Cubic inch (gr/in3)
Mass per volume density.
Pound per Cubic foot — sources
- NIST Handbook 44 — General tables of units including US customary density measures.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many grain per cubic inches are in 1 pound per cubic foot?
1 pound per cubic foot equals 4.050925926 grain per cubic inches, using the exact defined conversion factor rather than an estimate.
How do I convert pound per cubic foot to grain per cubic inch?
Multiply the pound per cubic foot value by 4.050925926. The converter above does this instantly to whatever precision you set.
How do I convert grain per cubic inch back to pound per cubic foot?
Use the reverse factor: 1 grain per cubic inch equals 0.2468571429 pounds per cubic foot. You can also use the swap control in the converter above to flip the direction instantly.
What is a pound per cubic foot?
Pound per Cubic foot (lb/ft3) measures density. The US customary unit for expressing density, commonly used in construction and engineering material specifications. It is classified as a US customary density unit.
What is a grain per cubic inch?
Grain per Cubic inch (gr/in3) is a unit of density.
Is the pound per cubic foot to grain per cubic inch conversion exact?
Yes. Both pound per cubic foot and grain per cubic inch are defined by fixed standards rather than physical artifacts, so the factor of 4.050925926 used above is exact to as many digits as you choose to display.
Where is the pound per cubic foot still used today?
United States (construction, engineering, materials specifications)
What's the difference between density and mass concentration?
Density is the mass of a pure substance or material per unit volume. Mass concentration is the mass of one component — like a dissolved solute — within a mixture's total volume. The two use the same kind of units but describe different physical situations.