Minecraft wiki entry for Coal, associated text: When used in a furnace as a fuel, a piece of coal lasts 80 seconds (smelting up to 8 items), like charcoal. Coal used as fuel lasts more than 5 times longer than wood planks or wood logs used as fuel, being more efficient than any other use of wood for smelting in Java Edition, but outstripped by wooden slabs in Bedrock Edition.