Hi Reji. I presume you mean the circumference of the teak pole is 60 inches (and that this is consistent or an average all the way along the length of the pole).

You can use our volume calculator to find the volume of wood if you like.

Since you want the volume in cubic feet, we first convert the measurements to feet:

pole length = 20 feet
circumference = 60 inches = 60/12 feet = 5 feet.

The volume of wood is the length of the pole times the cross-sectional area. A circle (the cross-section) has an area equal to π times the square of the radius. The radius is the circumference divided by 2π.

So the volume of the wood you have is:

Volume
= pole length × cross-sectional area
= pole length × π × radius²
= pole length × π × [circumference ÷ (2π)]²
= pole length × circumference² ÷ (4π)

Thus your volume of wood in cubic feet is 20 × 5² ÷ (4π).

Cheers,
Stephen La Rocque