OK, Jan. The circumference is the distance around the circle. Say you have
a round pond that's ten foot across. You'll need 31.4 feet of edging
stones. Say it's ten feet deep and you want to tile the side. You'll need
314 sq. ft. of tile.

It would hold 3.14*5*5*10*7.48= 5872 gallons.

Pi (3.14) X radius squared X diameter X 7.48 = gallons

How's that? ~ jan
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Zone 7a, SE Washington State
Ponds: www.jjspond.us