Double the depth and add that number to both the other measurement.

length + 2 feet + (2 x depth)

 x

 width + 2 feet + (2 x depth) = size of liner

For example a pond that measures 8 ft x 6ft and is 2 ft deep, you will need a liner 14ft ( 8 + 2 + 4) by 10ft ( 6 + 2 + 4).  The 2 extra feet is or overhang all around the edge of the pond.

 

Here is something new that I just learned:

Did you know that there is a difference between a wildlife pond and a natural pond?

A natural pond and a formal pond are more similar in set-up with plants and the fish they contain.  A natural and formal pond may attract wildlife, but even more will be attracted with  a wildlife pond.

• the wildlife pond does not contain koi
• can have fish but native species are used and may not be stocked until the other toads, frogs, etc. are established