If you use a dense stump killer that's not diluted, expect the process to take two weeks for the tree to die completely. But will less diluted and effective formulas, the process can take six weeks or longer. However, the sturdiness of the tree species and environmental factors also have an impact. If you're looking for a much faster solution consider using a stump grinder to grind the tree stump. Burning the tree stump is also a much faster solution.