Dokar Ohm wata ka’ida ce ta asali a ilimin kimiyyar lissafi da injiniyan lantarki wanda ke da alaƙa da halin yanzu da ke gudana ta hanyar madugu zuwa ƙarfin lantarki da ke cikinsa da juriya na madugu. Ya bayyana cewa na yanzu (I) da ke wucewa ta cikin madugu yana daidai da ƙarfin lantarki (V) da ake amfani da shi a cikinsa, yayin da ya yi daidai da juriya (R) na mai gudanarwa. A ilimin lissafi, ana bayyana Dokar Ohm a matsayin:V = I * RInda: V yana wakiltar wutar lantarki da aka auna a volts (V). I wakiltar halin yanzu da aka auna a amperes (A).R yana wakiltar juriya da aka auna a cikin ohms (Ω).Ohm's Law is mai suna Georg Simon Ohm masanin kimiyyar lissafi dan kasar Jamus, wanda ya tsara ka'ida a farkon karni na 19. Ana amfani da shi sosai a cikin bincike da ƙira na da'irori na lantarki kuma yana aiki a matsayin mahimman ra'ayi don fahimtar halayen resistors da sauran abubuwan lantarki.