Units & Conversion · 公制与英制 · Updated 2026-10-25
What Is Metric vs Imperial?
Definition
The US is the last major economy on customary units: 1 in = 2.54cm, 1 mi = 1.609km, 1 lb = 453.6g, 1 US gal = 3.785L (UK gal 4.546L). NASA lost a $327M Mars probe to a lb/N mix-up in 1999.
Formula
1 in = 2.54cm; 1 lb = 453.6g; US gal ≠ UK gal
Worked Example
1 cup = 237ml; 65 mph = 105 km/h; 150 lb = 68kg; 10 US gal = 37.9L.
Common Misconception
"All ounces are the same" - the troy ounce (gold/silver, 31.1g) is not the avoirdupois ounce (28.35g); "US and UK gallons are interchangeable" - they differ by 20%; watch fuel economy and wine buying across borders.
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