Firemaking

Burn logs from your inventory to gain Firemaking XP. Each log burned produces ashes which can be scattered for bonus Prayer XP and can also be used for bonuses in farming, herblore, and runecrafting.

Tinderboxes

Equip a tinderbox to multiply how many logs you can burn per session. Higher-tier tinderboxes require a higher Firemaking level.

Tinderbox tier efficiency multiplier

Depending on the difference in tier between the tool used for burning and the item you are burning, you can receive an additional mult to your standard tool efficiency. The effect of this is that you can craft items with lower tiers potentially much faster than items with higher tiers if you have higher-tiered tools.

For normal tools, their tier is determined by their minimum level required to equip. For the Heirloom Tinderbox, its tier is defined by your current firemaking level. The heirloom's tool efficiency itself is calculated separately as described in Heirlooms.

For items, their tier depends on the minimum required level for burning.

The level ranges for each tier and the associated tools are defined as below:

The exact multiplier you get applied to your tool efficiency depends on the tier difference as calculated using the formula: $Tier\ difference = tool\ tier - item\ tier$. The tool efficiency is multiplied as per the table below (— indicates no mult applied)