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How Much Does a Gallon of Water Weigh?

A US gallon of water weighs about 8.34 pounds (roughly 3.78 kilograms) at room temperature. A UK imperial gallon, which is larger, weighs about 10.02 pounds (roughly 4.55 kilograms).

Measurements & Conversions

Quick reference:

  • 1 US gallon ≈ 8.34 lb ≈ 3.78 kg
  • 1 imperial gallon ≈ 10.02 lb ≈ 4.55 kg
  • 1 liter of water ≈ 1 kg (2.2 lb)

Water weight changes slightly with temperature because water expands as it warms. It is densest at about 4°C (39°F), where it weighs the most, and becomes slightly lighter as it heats up. For everyday purposes, though, 8.34 pounds per US gallon is the standard figure to remember.

The closest sibling pages are How Much Is 8 oz in Cups? and How to Measure Hips?.

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