If you’re in doubt which sauna stones to buy this article will explain essential differences and important factors while choosing the stones.

Different size of sauna rocks

The usual size of stones is between softball and golf ball, which means in diameter 20-30 cm. This is the best choice. Different size sauna rocks hold heat (thermal mass) differently and release steam differently from a water being tossed on hot sauna rocks. Wood burning sauna stove or electric sauna stove will heat your sauna rocks, and the water turning into steam will temporarily cool off your sauna rocks. Bigger stones hold more heat, while smaller react quicker to the water when turning it into vapor. Combination of different sizes of rocks is the best.

Igneous or volcanic rocks

Formed in a molten environment, are the oldest rocks on the Earth. They result from cooled magma and lava. Most known are granite, basalt, and dolomite. But, volcanic rocks don’t hold thermal mass which creates thermal heat. However, it is not the porous and it is lighter in weight. Do not choose rocks from wet environments because it may have water trapped inside and because of that have a potential to explode. Buy it from approved sellers.


Formed as layers of compacted sediments, break easily and lightweight.


Heavy and dense, started out as sedimentary and changed by heat and pressure. Most known is marble.

Granite rocks

The best choice is rounded aged granite rocks without cracks or crevices. There is a fear that sauna rocks can explode, and it is true if using rocks that allow for water to get in cracks. But, there is no fear if use non-porous granite rocks on top of your sauna stove.

If you buy online, we recommend certified manufacturer such as those on Amazon Finnish Sauna Heater Rocks.

How to decide is stone dense enough?

Heavy and dense stones tend to produce more consistent heat and hold the heat better to produce steady steam. Try hitting them with a hammer or dropping them from waist level to a hard floor few times. If it doesn’t break or only chip a little, it is good.

Another test make outdoors. Place stones in the fire and wait to reach the high temperature. Use tongs and plunge the rocks into the bucket of cold water. When they are cool, inspect them for cracks and breaks.

Why sauna rocks?

The earliest form of the sauna was a room with a pile of rocks, without a chimney where rocks are heated by the fire with lots of wood and for a prolonged time. When the fire goes out all that heat stays contained within the rocks. The similar principle with heated rocks is in modern saunas.

Buying sauna rocks is a process, while their cleaning is very simple. Once a year clean the rocks and change them every two years. Bigger stones can be used longer, five to six years.