# How Much Does a Gallon of Water Weigh

> A US gallon of water weighs approximately 8.34 pounds (3.78 kg) at room temperature. An Imperial gallon weighs about 10.02 pounds. Compare weight and volume.

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**Category:** Conversions

## Quick Answer

Determine the exact weight of water in pounds or kilograms for US and Imperial liquid gallons.

## Definition

A gallon-of-water-weight page calculates water mass based on volume. At room temperature, a US liquid gallon weighs approximately 8.34 pounds (3.78 kilograms). An Imperial (UK) gallon weighs about 10.02 pounds (4.55 kilograms). The Imperial gallon was defined in 1824 as the volume filled by 10 pounds of distilled water, which is where the round number comes from, but since 1985 it has been defined as exactly 4.54609 cubic decimetres and the water it holds no longer weighs a round 10 pounds. Water weight varies slightly depending on its temperature and density.

## How to Use

1. **Select liquid system** — Toggle US Customary or Imperial (UK) gallon measurements.
2. **Enter gallons or weight** — Type in the volume in gallons or the weight in pounds to run the bidirectional calculation.
3. **Observe metric equivalents** — Check the automatically calculated weight outputs in kilograms.

## Disclaimer

This calculator provides estimates for educational and planning purposes. Always consult a qualified professional for specific advice on financial, medical, legal, or other regulated decisions.

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