Volume Conversion

NIST SP 811 & SI / Imperial Volumetric Standards

The National Institute of Standards and Technology (NIST SP 811) defines exact conversion ratios for volume and fluid capacity.

Primary Volumetric Conversion Constants

• 1 US Liquid Gallon: 3.785411784 Liters = 231 in^3 = 128 fl oz = 4 quarts

• 1 UK Imperial Gallon: 4.54609 Liters = 1.20095 US Gallons

• 1 Cubic Foot (ft^3): 28.316846592 Liters = 7.48052 US Gallons = 1,728 in^3

• 1 Cubic Meter (m^3): 1,000.0 Liters = 264.172 US Gallons = 35.3147 ft^3

• 1 US Fluid Ounce: 29.5735295625 mL = 0.0295735 L

• 1 Petroleum Barrel (bbl): 42 US Gallons = 158.987 Liters

How to Use This Calculator

Enter your Volume Amount to Convert (e.g. 5.0), From Volume Unit — choose from US Liquid Gallons (gal), Liters (L), Milliliters (mL), and To Volume Unit — choose from US Liquid Gallons (gal), Liters (L), Milliliters (mL). Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Conversion factors (to SI base unit or reference unit):

us_gal: 3.785411784

liters: 1.0

ml: 0.001

cu_m: 1000.0

cu_ft: 28.316846592

cu_yd: 764.554857984

cu_in: 0.016387064

fl_oz: 0.0295735295625

quarts: 0.946352946

pints: 0.473176473

cups: 0.2365882365

imp_gal: 4.54609

Worked Example

A 5-gallon water jug contains exactly 18.93 liters (640 fluid ounces), occupying 0.67 cubic feet of space.

Understanding Your Result

Geometric calculations assume ideal shapes — real-world measurements should include a 5–15% tolerance for irregular shapes, cutting waste, and installation overlap. For construction applications: always verify calculated areas match your physical measurements before ordering materials. Standard practice is to measure the same dimension twice from different reference points and use the average. Express results in the units required by your supplier or building permit — conversions between cubic yards, cubic feet, and cubic meters must be precise for material orders.