Can I use a spice grinder for coffee beans?

Using a spice grinder for coffee is a common 'brewing hack' for beginners, but it is one that will almost certainly limit the quality of your coffee. Spice grinders are designed to pulverize dry ingredients into a fine powder, which works well for spices but is disastrous for coffee. Coffee brewing relies on the precise control of particle size to manage how water extracts flavor from the bean.

When you use a blade-based spice grinder, you have no control over the grind size. The blades spin at high speeds, creating a mixture of 'boulders' (large chunks) and 'fines' (dust). During brewing, the water hits these different sizes at different rates. The fines extract very quickly, often becoming bitter, while the boulders extract slowly, often remaining sour or underdeveloped. This lack of uniformity makes it nearly impossible to 'dial in' your brew or achieve a consistent flavor profile.

Furthermore, spice grinders often retain the oils and aromas of the spices you have previously ground. Unless you clean the device perfectly after every use—which is difficult given the design of most spice grinders—your coffee will likely take on the flavor of cumin, cinnamon, or whatever else you have processed. Coffee beans are highly porous and will readily absorb these lingering odors, ruining the delicate notes of your roast.

In practice, if you are serious about improving your coffee, a dedicated burr grinder is the most important piece of equipment you can buy. It doesn't have to be the most expensive model on the market, but the mechanism of crushing beans between two burrs is essential for consistency. If you are currently using a spice grinder, you will notice an immediate and significant improvement in clarity and sweetness the moment you switch to a burr grinder.