Volume Unit Conversions & Standards
Last updated: October 1, 2026 · Legal conversion factors defined by NIST SP 811
Exact conversion factors, mathematical relationships, and quick reference tables defined in accordance with the National Institute of Standards and Technology (NIST SP 811).
Cubic Feet to Gallons (US)
Standard conversion for water tanks, aquariums, swimming pools, and residential plumbing systems.
Liters to Cubic Meters
Primary metric conversion used in water billing, chemical engineering, and environmental science.
Cubic Inches to Liters
Essential for automotive engine displacement (converting cubic inches CI to engine liters L).
US Gallons to Liters
Liquid volume standard for international shipping, fuel capacity, and beverage production.
Important Distinction: US Liquid Gallons vs. Imperial (UK) Gallons
A common source of confusion in international fluid measurements is the difference between US and British Imperial gallons:
- 1 US Liquid Gallon = 231 cubic inches = 3.785411784 Liters = 128 US fluid ounces.
- 1 UK Imperial Gallon = 277.419 cubic inches = 4.54609 Liters = 160 Imperial fluid ounces (~20% larger).
Unless explicitly indicated otherwise, all calculators on VolumeCalculator.org use US Customary gallons (231 in³ / 3.785 L).