How to Convert US gallons to US fluid ounces (gal to fl oz)
Volume conversions help with baking from American recipes, comparing petrol prices quoted per gallon abroad with pump prices per litre here, and reading PUB water bills in cubic metres. This guide shows how to convert us gallons into us fluid ounces by hand, with examples and a quick-reference table.
The conversion
To convert us gallons to us fluid ounces, multiply the value by 128.0000676281. To go the other way, divide by the same number (or multiply by 0.0078124959). For a quick estimate, multiply by about 130.
US fluid ounces = us gallons × 128.0000676281
Worked examples
- 3 gal = 384.0002 fl oz
- 12.5 gal = 1,600 fl oz
- 75 gal = 9,600.01 fl oz
US gallons to US fluid ounces table
| US gallons | US fluid ounces |
|---|---|
| 1 gal | 128.0001 fl oz |
| 2 gal | 256.0001 fl oz |
| 5 gal | 640.0003 fl oz |
| 10 gal | 1,280 fl oz |
| 20 gal | 2,560 fl oz |
| 25 gal | 3,200 fl oz |
| 50 gal | 6,400 fl oz |
| 100 gal | 12,800.01 fl oz |
| 250 gal | 32,000.02 fl oz |
| 500 gal | 64,000.03 fl oz |
| 1,000 gal | 128,000.07 fl oz |
Common questions
Is gal to fl oz exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the US fluid ounces to US gallons converter.
Mistakes to avoid
Rounding the factor too early
Using 3 instead of 3.28 for feet per metre introduces an error of almost 9% before you have started.
Forgetting squared and cubed units
Area and volume factors are the length factor squared or cubed, so 1 m² is about 10.76 sq ft, not 3.28.
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Background
Unit conversion is simply multiplication by a fixed ratio. The ratio between two units of the same quantity never changes, so once you know it you can convert any value in either direction.
Singapore adopted the metric system in the 1970s, replacing imperial units and traditional Chinese measures in most official uses. Metric units are now standard in schools, trade and government, but older units survive in property, markets and imported goods.
For everyday use, three or four significant figures are usually enough. Engineering, science and trade documents may need more, and rounding should happen only at the end of a calculation.
For any value, use the US gallons to US fluid ounces Converter or browse all volume converters.
Run your own numbers: US gallons to US fluid ounces Converter