Estimating Your Pool Liner Size. Measure the length (ft) and width (ft) of the pool desired. Add twice the pool’s depth to each dimension plus an allowance of 1 foot for overlap at the edges. For example, a 5 x 10 foot, 2 foot deep pool requires a liner whose width is 5 + 4 (twice the depth) + 1 = 10 feet and whose length is 10 + 4 + 1 = 15. Thus a pool liner of 10 x 15 is required in this example. If you are in doubt, please call, we will help you with your calculations.