Wait, what?
A gallon isn’t always a gallon.
A U.S. gallon is about 3.785 L. An Imperial gallon is about 4.546 L—roughly 20% larger.
Standard-defined
Why this is interesting
Same word, same spelling, two different standardised quantities — which is exactly the kind of trap that makes recipes and fuel figures travel badly.
How this measurement works
Both gallons are exactly defined; they simply define different amounts. The U.S. liquid gallon is 3.785411784 L. The Imperial gallon is 4.54609 L. Neither is approximate, and neither is more correct — the label alone does not tell you which one is meant, so the source of the number matters.
See the math
- U.S. liquid gallon
- 3.785411784 L (exact)Source value
- Imperial gallon
- 4.54609 L (exact)Source value
- Ratio
- 4.54609 ÷ 3.785411784 ≈ 1.20Scaleidoscope calculation
- Difference
- The Imperial gallon is about 20% larger
How certain is this?
Standard-defined — both values are exact definitions of different units.
Both gallons are exactly defined; they are simply different units.
Keep going
- Bigger doesn't always mean tallerMauna Loa has at least about 75,000 km³ of volcanic material.
- Wait, what?A container packed with ping-pong balls can still be about 36% empty.
- Things in thingsAbout 1.3 million.
- Same amountOur Olympic-size pool reference equals about 5.3 million Starbucks Grandes.
- Same amountAbout 2.1 million 40-oz Stanley capacities equal our Olympic-size pool reference.
- Measurement trapAn “Olympic-size pool” doesn’t have one universal exact volume.