If you're not sure whether your miter saw blade is dull, there are a few ways to tell. First, take a close look at the teeth on the blade. If they appear to be worn down or chipped, it's time for a new blade. Second, try making a cut with the saw. If the cut is ragged or takes longer than usual to make, that's another sign that the blade is dull and needs to be replaced. Finally, if your miter saw seems to be vibrating more than usual when you use it, that could also be a sign of a dull blade.