It depends on the filer basket of your percolator. If the filter basket of the percolator you own is as good as a regular coffee machine, you can use regular ground coffee.nnBut most of the time, the percolator’s filter basket comes with a subtle basket that makes it hard for regular coffee.nnSo, if the filter basket is not as good, you should use a coarser grind to avoid ending up with the grounds in your coffee.