Conversion formula

The conversion factor from fluid ounces to gallons is 0.0078125, which means that 1 fluid ounce is equal to 0.0078125 gallons:

1 fl oz = 0.0078125 gal

To convert 640 fluid ounces into gallons we have to multiply 640 by the conversion factor in order to get the volume amount from fluid ounces to gallons. We can also form a simple proportion to calculate the result:

1 fl oz → 0.0078125 gal

640 fl oz → V_(gal)

Solve the above proportion to obtain the volume V in gallons:

V_(gal) = 640 fl oz × 0.0078125 gal

V_(gal) = 5 gal

The final result is:

640 fl oz → 5 gal

We conclude that 640 fluid ounces is equivalent to 5 gallons:

640 fluid ounces = 5 gallons

Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 gallon is equal to 0.2 × 640 fluid ounces.

Another way is saying that 640 fluid ounces is equal to 1 ÷ 0.2 gallons.

Approximate result

For practical purposes we can round our final result to an approximate numerical value. We can say that six hundred forty fluid ounces is approximately five gallons:

640 fl oz ≅ 5 gal

An alternative is also that one gallon is approximately zero point two times six hundred forty fluid ounces.

Conversion table

fluid ounces to gallons chart

For quick reference purposes, below is the conversion table you can use to convert from fluid ounces to gallons