Convert Inches per Hour to Gallons per Day per Square Foot

Formula

gpd/ft² = in/h × 14.96103896104

Derivation from SI units:

• 1 in/h = 0.0254/3600 m/s.
• 1 gpd/ft² = 0.003785411784 m³ ÷ 86,400 s ÷ 0.09290304 m².
• 1 in/h = 0.000007055555555556 m/s ÷ 4.715952932099 × 10⁻⁷ m/s per gpd/ft² = 14.96103896104 gpd/ft²

Both units are defined exactly, so the factor is exact. Inch per Hour definition: inch per hour; Gallon per Day per Square Foot definition: US gallon per day per square foot.

Worked examples

1. A reading of 0.5 in/h converts to 7.480519481 gpd/ft².
   0.5 in/h × 14.96103896 = 7.480519481 gpd/ft²
2. A value of 3 in/h is 44.88311688 gpd/ft².
   3 in/h × 14.96103896 = 44.88311688 gpd/ft²

Where it's used

Inches per Hour are used for USDA soil survey permeability classes, while US gallons per day per square foot appear in older USGS and well-driller reports. Both measure hydraulic conductivity (coefficient of permeability k), so the conversion is a fixed factor.

Inch per Hour to other hydraulic conductivity units

Frequently asked questions

Sources

• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "inch".
• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "gallon (U.S.)".

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.