Convert US gallons to US fluid ounces
1 US gallon is 128 fl oz. One US gallon is exactly 128 US fluid ounces.
One US gallon is 128 US fluid ounces. To convert US gallons to US fluid ounces, multiply by 128; to go the other way, divide by 128 or multiply by 0.0078125. The factor is exact rather than rounded: it follows from NIST Handbook 130. Exactly 231 cubic inches.
Factor checked against the defining standard · How we check
- US gallons × 128
1 * 128128 fl oz
1 US gallon in every volume unit
| Unit | Value | Exact factor |
|---|---|---|
| US teaspoons | 768 tsp | × 768 |
| US tablespoons | 256 tbsp | × 256 |
| US fluid ounces | 128 fl oz | × 128 |
| US cups | 16 cup | × 16 |
| US pints | 8 pt | × 8 |
| US quarts | 4 qt | × 4 |
| US gallons (as entered) | 1 gal | — |
| milliliters | 3,785.411784 ml | × 3,785.411784 |
| liters | 3.785411784 L | × 3.785411784 |
| imperial gallons | 0.8326741846 gal (UK) | × 0.832674184629 |
| imperial quarts | 3.330696739 qt (UK) | × 3.33069673852 |
| imperial pints | 6.661393477 pt (UK) | × 6.66139347703 |
| imperial fluid ounces | 133.2278695 fl oz (UK) | × 133.227869541 |
| imperial gills | 26.64557391 gi (UK) | × 26.6455739081 |
| cubic millimetres | 3,785,411.784 mm³ | × 3,785,411.784 |
| cubic centimetres | 3,785.411784 cm³ | × 3,785.411784 |
| cubic inches | 231 in³ | × 231 |
| cubic feet | 0.1336805556 ft³ | × 0.133680555556 |
| cubic yards | 0.004951131687 yd³ | × 0.00495113168724 |
| cubic metres | 0.003785411784 m³ | × 0.003785411784 |
Factors are entered by hand from NIST Handbook 130 rather than derived from a units library, so the ones that terminate are exact rather than rounded.
How do you convert US gallons to US fluid ounces? The converter and the working
- 1.Take the measurement in US gallons.
- 2.Multiply by 128 — that is how many US fluid ounces fit in one US gallon.
- 3.To go back the other way, divide by 128, or multiply by 0.0078125.
Worked example: 25 US gallons to US fluid ounces
- Formula
- gal × 128 = fl oz
- Arithmetic
- 25 × 128 = 3,200 fl oz
- Answer
- 25 gal = 3,200 fl oz
The factor is exact, so this figure is exact too — only the display is rounded.
US gallons to US fluid ounces conversion table
| US gallons | US fluid ounces |
|---|---|
| 1 gal | 128 fl oz |
| 2 gal | 256 fl oz |
| 3 gal | 384 fl oz |
| 4 gal | 512 fl oz |
| 5 gal | 640 fl oz |
| 6 gal | 768 fl oz |
| 7 gal | 896 fl oz |
| 8 gal | 1,024 fl oz |
| 9 gal | 1,152 fl oz |
| 10 gal | 1,280 fl oz |
| 12 gal | 1,536 fl oz |
| 15 gal | 1,920 fl oz |
| 20 gal | 2,560 fl oz |
| 25 gal | 3,200 fl oz |
| 50 gal | 6,400 fl oz |
| 100 gal | 12,800 fl oz |
| 200 gal | 25,600 fl oz |
| 300 gal | 38,400 fl oz |
| 500 gal | 64,000 fl oz |
| 1000 gal | 128,000 fl oz |
| 2000 gal | 256,000 fl oz |
| 5000 gal | 640,000 fl oz |
| 10000 gal | 1,280,000 fl oz |
The US gallon holds 128 fluid ounces, the imperial one 160
A US fluid ounce is one 128th of a US gallon; an imperial fluid ounce is one 160th of a larger gallon. So the two ounces differ by about four per cent and the two gallons by twenty. A UK recipe asking for 10 fl oz means 284 ml and a US one means 296 ml, and neither converts by moving a decimal point.
NIST Handbook 44, Appendix C — general tables of units of measurement
What is a US gallon?
Exactly 231 cubic inches. The imperial gallon is 4.546 liters, so US and UK fuel economy figures are not comparable.
What is a US fluid ounce?
Exactly one 128th of a US gallon, which makes it 29.5735295625 ml exactly. The imperial fluid ounce is a different unit at exactly 28.4130625 ml, so a UK recipe calling for 10 fl oz means 284 ml and a US one means 296 ml. It is also a volume, not a weight: an ounce of flour is not a fluid ounce of flour.
How many US fluid ounces are in a US gallon?
One US gallon is 128 US fluid ounces, exactly. Going the other way, one US fluid ounce is 0.0078125 US gallons. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every volume unit here
The whole group — 20 units with their symbols and the size of each one in liters — is on the conversion index, along with every pair it makes. The table above already gives each of them relative to a US gallon.
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Questions people actually ask
- How many US fluid ounces are in a US gallon?
- 128. Exactly one 128th of a US gallon, which makes it 29.5735295625 ml exactly. The imperial fluid ounce is a different unit at exactly 28.4130625 ml, so a UK recipe calling for 10 fl oz means 284 ml and a US one means 296 ml. It is also a volume, not a weight: an ounce of flour is not a fluid ounce of flour.
- How do I convert US fluid ounces back to US gallons?
- Divide by 128, or multiply by 0.0078125 — they are the same operation.
Other volume conversions
US fluid ounces to US gallons — the same conversion the other way.