Conversion formula

The conversion factor from cubic inches to gallons is 0.0043290043290138, which means that 1 cubic inch is equal to 0.0043290043290138 gallons:

1 in3 = 0.0043290043290138 gal

To convert 688 cubic inches into gallons we have to multiply 688 by the conversion factor in order to get the volume amount from cubic inches to gallons. We can also form a simple proportion to calculate the result:

1 in3 → 0.0043290043290138 gal

688 in3 → V_(gal)

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

V_(gal) = 688 in3 × 0.0043290043290138 gal

V_(gal) = 2.9783549783615 gal

The final result is:

688 in3 → 2.9783549783615 gal

We conclude that 688 cubic inches is equivalent to 2.9783549783615 gallons:

688 cubic inches = 2.9783549783615 gallons

Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 gallon is equal to 0.33575581395275 × 688 cubic inches.

Another way is saying that 688 cubic inches is equal to 1 ÷ 0.33575581395275 gallons.

Approximate result

For practical purposes we can round our final result to an approximate numerical value. We can say that six hundred eighty-eight cubic inches is approximately two point nine seven eight gallons:

688 in3 ≅ 2.978 gal

An alternative is also that one gallon is approximately zero point three three six times six hundred eighty-eight cubic inches.

Conversion table

cubic inches to gallons chart

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