Formulas for calculating any combination of electrical units

V comes from "voltage" and E from "electromotive force emf". E means also energy, so let's choose V. Energy = voltage × charge. E = V × Q. Some like better to stick to E instead to V, so do it. 
Voltage V = I × R = P / I = √(P × R) in volts V Current I = V / R = P / V = √(P / R) in amperes A Resistance R = V / I = P / I^{2 } = V^{2}/ P in ohms Ω Power P = V × I = R × I^{2}= V^{2}/ R in watts W 
Electric voltage = amperage × resistance
Please enter two values, the third value will be calculated.
Electric power = amperage × voltage
Please enter two values, the third value will be calculated.
If the unit of power P = I × V and of voltage V = I · R is needed
look for "The Big Power Formulas":
Calculations: Power (watt), voltage, current, and resistance