Go with the longest and widest measurements for an irregular pool.

Measure the maximum length and the maximum width of your pool at its extremes. Add one to two feet to each measurement. That’s the cover size you need.

Pool cover manufacturers assume you’re buying a rectangle. Even for kidney-shaped or freeform pools, a rectangular cover sized to the farthest points works fine. The excess flaps over the edges — that’s what the water bags or cable anchors are for. You’re not trying to get a perfect fit; you’re trying to keep leaves and debris out and prevent evaporation.

Custom covers exist, but they cost more, take longer to ship, and rarely sit perfectly anyway. Unless your pool is a genuine oddity (like a pentagon or a figure-eight), a properly oversized rectangle cover will do the job. Measure twice, add a foot, order once.

This is not the place to try and save an inch.