ConvBolt — Unit ConverterUS gallons to Fluid ounces Converter
Converting US gallons to fluid ounces is a multiplication by a fixed factor: 1 gal = 128 fl oz. The table below covers the values people look up most often, and the formula section shows exactly where that factor comes from.
Because one us gallon works out to 128 fl oz, the fluid ounce is the far larger unit of the two: a figure given in fluid ounce always carries a larger number than the same measurement in us gallon. A chart drawn in gal can hide that, so check which label the axis uses before you compare two readings.
Kitchen and workshop measuring are where this pair comes up: a jug marked in US gallons alongside a recipe or container printed in fluid ounces is the classic case, and it is why the two labels rarely agree to the eye.
The conversion factor used here is 128 fl oz per us gallon (0 significant digits as shown). Kept to seven figures it covers professional measurement; if you round it to two or three decimals for a spreadsheet, the error scales with the input — at a value of 1,000 gal a factor rounded to three decimals can be off by a measurable amount. The reverse direction uses 0.0078125 gal per fl oz, the exact reciprocal, so a round trip through both pages returns your original number.
US gallons to Fluid ounces formula
Use this formula to convert any us gallon value to fluid ounces:
Worked example: 100 gal × 128 = 12800 fl oz.
US gallons to Fluid ounces conversion table
| US gallons (gal) | Fluid ounces (fl oz) |
|---|---|
| 0.5 gal | 64 fl oz |
| 1 gal | 128 fl oz |
| 2 gal | 256 fl oz |
| 5 gal | 640 fl oz |
| 10 gal | 1280 fl oz |
| 20 gal | 2560 fl oz |
| 50 gal | 6400 fl oz |
| 100 gal | 12800 fl oz |
| 500 gal | 64000 fl oz |
| 1000 gal | 128000 fl oz |
How to convert US gallons to fluid ounces
Multiply the us gallon value by 128 to get the equivalent in fluid ounces. This single factor works for every value in the table above and for anything else you need — there is no per-value adjustment, which is why a conversion table and a calculator always agree.
If you need the opposite direction, use the Fluid ounces to US gallons converter instead of dividing by hand; both pages use the same source factors. For every other gal conversion in one place, see the gal conversion hub.
Frequently asked questions
How many fluid ounces are in 1 us gallon?
1 us gallon = 128 fl oz.
What is 100 US gallons in fluid ounces?
100 gal = 12800 fl oz.
Is converting US gallons to fluid ounces the same as fluid ounces to US gallons?
No — the direction changes the multiplier. The reverse conversion (1 fl oz = 0.0078125 gal) is on the Fluid ounces to US gallons page.
Related conversions
Try the ConvBolt Unit Converter for any other volume unit, browse the Volume conversions, or read our conversion guides.