640 US customary cups in US gallons

Conversion formula
How to convert 640 US customary cups to US gallons?

We know (by definition) that: $1\mathrm{uscup}\approx 0.0625\mathrm{usgallon}$

We can set up a proportion to solve for the number of US gallons.

Now, we cross multiply to solve for our unknown $x$:

Conclusion: 640 ⁢ uscup ≈ 40.0 ⁢ usgallon

Conversion in the opposite direction

The inverse of the conversion factor is that 1 US gallon is equal to 0.025 times 640 US customary cups.

It can also be expressed as: 640 US customary cups is equal to $\frac{1}{\mathrm{0.025}}$ US gallons.

Approximation

An approximate numerical result would be: six hundred and forty US customary cups is about zero US gallons, or alternatively, a US gallon is about zero point zero three times six hundred and forty US customary cups.