Dokar rarraba Boltzmann doka ce ta kididdiga a kimiyyar lissafi wacce ke bayyana rarraba barbashi a cikin tsarin a cikin ma'aunin zafi. Sunan dokar ne bayan wani masanin kimiyyar lissafi dan kasar Austria Ludwig Boltzmann, wanda ya kirkiro ta a karshen karni na 19. Dokar ta bayyana cewa a cikin tsarin da aka ba da zafin jiki, yuwuwar gano barbashi tare da wani matakin makamashi yana daidai da ma'aunin Boltzmann, wanda aka ba da shi ta hanyar ma'auni na mummunan makamashi da aka raba ta samfurin Boltzmann akai-akai da kuma zafin jiki. Wannan doka tana da mahimmanci wajen fahimtar halayen barbashi cikin ma'auni na thermal kuma ana amfani dasu sosai a fannoni daban-daban na kimiyyar lissafi, sunadarai, da injiniyanci.