The ideal candle size depends on the lantern’s dimensions. Generally, use candles that are no taller than two-thirds the height of the lantern and no wider than half the base width. For smaller lanterns, tea lights or votive candles work well, while medium-sized lanterns can accommodate pillar candles up to 3 inches in diameter. Ensure the flame has enough clearance to avoid heat damage to the lantern. LED candles of similar size are also a safe and convenient alternative.