Are you talking container candles or Pillar candle? I usually go with 1 wick up to 3" diameter Pillar candle, and then go to 2 wicks on anything bigger then that up to 4" and then I jump to 3 wicks. On container candles so much depends on the size of the wick being used, but I usually go with 1 with up to 3" diameter container and then go to a 3 wick on anything bigger. So much is trial and error until you find what works.