Figure a 2-inch bed of mason sand — for a 15-ft round pool that's about 1.1 cubic yards, so order 1.5–2 to leave room for leveling. The math: 177 sq ft × 2 inches ÷ 324. Flat and consistent beats deep; humps and dips telegraph straight through a liner.
Sand bed sizing by pool
| Round pool | 2" bed | Order |
|---|---|---|
| 15 ft (~177 sq ft) | ~1.1 cy | 1.5–2 cy |
| 18 ft (~254 sq ft) | ~1.6 cy | 2 cy |
| 24 ft (~452 sq ft) | ~2.8 cy | 3 cy |
Water finds every low spot, so screed with a straight board and check level twice before the liner goes down. Mason sand screeds smooth under a liner; concrete sand is the coarser option some installers prefer under a base ring. Check your size with the material calculator.
