Electric Resistance Calculator

Calculate the electrical resistance in ohms from voltage in volts and amperage in amperes. The electrical conductance in siemens, which is the counterpart to the resistance, is also calculated.

The formulas are:
R = U / I
G = I / U
G = 1 / R

The units are:
1Ω = 1V / 1A
1S = 1A / 1V

Please enter two values, but not resistance and conductance together. The other values will be calculated. The units can be selected with different prefixes, such as milli- or kilo-.

Example: at a voltage of 10 mV and a current of 2 A, the amperage is 5 mΩ and the corresponding conductance is 200 siemens.
A power line has a resistance of about 0.1 ohms per kilometer. At a voltage of 110 kilovolts, 1.1 megaamperes flow through it. This is only a theoretical and very simplified view; electrical networks are much more complicated. In the case of a power line, the current strength depends primarily on how much is ultimately consumed.

Electrical resistance can be described colloquially as how difficult it is for the current to flow through a conductor. The higher the resistance, the more difficult it is and the less current reaches the other end. The loss generates heat and releases it into the environment. Poor conductors therefore become hotter than good conductors. There is of course a risk that the conductors will burn out.
From a physical point of view, electrical resistance is the opposite of the ability of the valence electrons of the conductor material to move freely within the conductor. In a good conductor, i.e. one with low resistance, these electrons can move like the molecules in a gas. The valence electrons are those in the outermost shell of the atomic nucleus; the electrons further inside are not mobile in such a way. In a poor conductor, on the other hand, the valence electrons are more strongly bound to the atomic core.