Ohm'sLawCalc

With this app you can calculate one of the three values of your Ohm's Law-circuit. You only need to put two values and tap calculate-button and the app will calculate the third value. 

For voltage unit (Volt), the app supports pV, nV, µV, mV, V, KV, MV, GV.
For current unit (Amper), the app supports pA, nA, µA, mA, A, KA, MA, GA.
For resistance unit (Ohm), the app supports pΩ, nΩ, µΩ, mΩ, Ω, KΩ, MΩ, GΩ.
For power unit (Watt), the supports pW, nW, µW, mW, W, KW, MW, GW.

You can change the units by tapping the unit-label.