644 US dry barrels in US gallons
Result
The conversion result is: 644 US dry barrels is equivalent to 19671.2727272727 US gallons.[1]
Conversion formula
How to convert 644 US dry barrels to US gallons?
We know (by definition) that: 1 drybarrel ≈ 30.5454545454545 usgallon.
We can set up a proportion to solve for the number of US gallons.
1 drybarrel / 644 drybarrel ≈ 30.5454545454545 usgallon / x usgallon
Now, we cross multiply to solve for our unknown x:
x usgallon ≈ (644 drybarrel / 1 drybarrel) * 30.5454545454545 usgallon → x usgallon ≈ 19671.2727272727 usgallon
Conclusion:
644 drybarrel ≈ 19671.2727272727 usgallon

Conversion in the opposite direction
The inverse of the conversion factor is that 1 US gallon is equal to 5.08355516119491e-05 times 644 US dry barrels.
It can also be expressed as: 644 US dry barrels is equal to 1 / 5.08355516119491e-05 US gallons.
Approximation
An approximate numerical result would be: six hundred and forty-four US dry barrels is about nineteen thousand, six hundred and seventy-one point two seven US gallons, or alternatively, a US gallon is about zero times six hundred and forty-four US dry barrels.
Footnotes
[1] The precision is 15 significant digits (fourteen digits to the right of the decimal point).
Results may contain small errors due to the use of floating point arithmetic.