Furnace Calculator
Pick what to smelt, how many, the device and the fuel — the calculator shows the time, the XP and how much fuel to put in.
How we calculate
A regular furnace spends 10 seconds per item. The blast furnace (ores, raw metals and metal gear only) and the smoker (food and kelp only) run twice as fast — 5 seconds — but fuel also burns out twice as fast in them. So one unit of fuel smelts the same number of items in any of the three: coal does 8, a lava bucket does 100.
XP is an average: each recipe has its own value per item, such as 0.7 for an iron ingot or 1 for a gold ingot. The game pays out the fractional part with matching probability when you collect the output, so on large batches the total lands close to the estimate. Fuel is rounded up to whole units, because a partly used unit still burns out completely. With several furnaces side by side, items are split evenly, the time drops, and fuel is counted for each furnace separately.
Cooking time, XP and the recipe list come straight from the 26.3 recipe files, while fuel burn time and the blast furnace and smoker speed-up come from the new fuel component, which also became part of the game data in 26.3.
Sources
checked 30 September 2026
Questions and answers
Does a blast furnace save fuel?
No. The blast furnace and smoker smelt twice as fast, but fuel burns half as long in them, so one unit of fuel still covers the same number of items as in a regular furnace. You only save time.
Which fuel is the most efficient?
A Lava Bucket smelts 100 items, a Block of Coal 80, a Dried Kelp Block just over 20. Coal and charcoal do 8 items each, planks and logs 1.5 each.
Why is the XP a fraction?
Recipes store XP as a fraction, such as 0.7 per iron ingot. The game rounds it randomly when you take the output out of the furnace, so the calculator shows the average you can expect.
Which version are these numbers for?
Java Edition 26.3. In this version the blast furnace and smoker speed comes from the fuel rather than the recipe, but for players the time and fuel use are the same as before.
Unofficial tool. Not affiliated with the developers or publishers of Minecraft.