You know the circumference of the base.
From that, you can derive the radius as follows:
C = 2 * pi * r, where:
C = circumference
r = radius
Replace C in this formula with 23 inches and you get:
23 = 2 * pi * r
Divide both sides of this equation by 2*pi and you get:
23 / (2*pi) = r
Solve for r to get:
r = 3.660563691.
That's your radius.
Now go back to your volume formula of V = pi*r^2*h
You have:
r = 3.660563691 and you have h = 12
You can replace these values in the formula to get:
V = pi * (3.660563691)^2 * 12.
This gets you:
V = 505.1577894 cubic inches.
You can translate this to quarts or pints or cups by using the translation formulas that are available.
505.1577894 cubic inches is equal to:
2.1868302571429 gallons
8.7473210285714 quarts
17.494642057143 pints
34.989284114286 cups
279.91427291429 ounces
You would obviously want to round this off to the nearest unit to get a rough measure.
Those rough measures would be:
approximately 2 gallons
approximately 9 quarts
approximately 17 pints
approximately 35 cups
approximately 280 ounces
.