The next function provides the column "X" and row "Y" of any spiral index very quickly. Best of luck. rec BuildSpiralIndex(long w, long h, long index = -1) { long count = 0 , x = -1, y = -1, dir = 1, phase=0, pos = 0, length = 0, totallength = 0; bool isVertical = false; if(index>=(w*h)) return null; do { isVertical = (count % 2) != 0; length = (isVertical ? h : w) - count/2 - count%2 ; totallength += length; count++; } while(totallength 1 ? phase : w - phase); y = ((pos == 1 || pos == 2) ? h - phase : phase) + (1 * (pos == 3 ? 1 : 0)); dir = pos > 1 ? -1 : 1; if (isVertical) y -= (totallength - index - 1) * dir; else x -= (totallength - index -1) * dir; return new rec { X = x, Y = y }; }