How to calculate the volume of a terra cotta pot?

[Paul Mc]

I am attempting to buy some potting mix online but I can't seem to figure out how to calculate the volume of this terra-cotta pot. It's the round type that you can buy at any Home Depot or Lowes, tapers a bit towards the bottom.

Mine was labeled as a 12" pot.

[Ray]

If it's the typical tapered, straight-sided pot:

Average the inside diameter at the top and at the bottom. Halve it to get the average radius.

Square that, and multiply by pi (3.14159) to get the average cross-sectional area, and multiply that by the depth of the pot, to get its volume.

[james mickelso]

.785xdia squared x depth all in inches then divide that by 1728 (that's how many cubic inches in a cubic foot)to get cubic feet which is how you buy any soil, bark, perlite. So 6x6x.785x6divided by1728 equals..................0987 ft cubed. a 4 inch pot would be 4x4x.785x4/1728 equals.....0298 cubic foot. Or just buy a 1 cubic foot bag and have fun.

[james mickelso]

Oh. Pie x r squared is the same as .785 x diameter squared. Or 3.14 times r times r equals .785 times diameter squared. So..... 6x6x.785 =28.26 which is 3x3x3.14 or 28.26.

[silken]

Now I have a headache!

[Paul Mc]

LOL, me too. Thanks for all of the info on calculations guys - I used it and hope I bought the right amount of medium for my cymbidium. If I did not, I guess I will amend it with some perlite or something. Guess it's time to study up on appropriate mediums for cymbidiums so I amend it appropriately.