Scientists spent years after Edison's invention in 1879 trying to decipher electricity. Now, we know all there is know about electricity, including what we'll be focusing on today: electrical resistivity.

    Below, we'll answer some important questions surrounding this property, from what it is, to how resistivity units are measured and converted.

    If the idea of converting resistivity units sounds too difficult, don't worry! All you have to do is try our resistivity calculator to get accurate conversions in an instant.


    What is electrical resistivity?

    It may come as a surpise but, it is not actually a measurement of electricity. It's a measurement related to the object electricity moves through.

    Simply put, electrical resistivity is a property that measures how strongly an object resists the flow of an electrical current.

    An object that electricity doesn't flow through is an object with high electrical resistivity.

    This is the opposite of another fundamental property, electrical conductivity. Conductivity measures how easily electricity moves through an object.

    What is the standard unit of resistivity?

    Electrical resistivity is most often represented by the Greek letter ϱ, or rho.

    The SI unit for resistivity is the ohm-meter, which uses the following symbol: Ω·m.

    When would you have to convert resistivity?

    Resistivity, once formulated, doesn't typically need to be converted to anything else. It's most-often used unit is ohm-meters.

    However, when it comes to the resistivity values of certain materials, you'll likely see those readings listed in micro-ohm centimeters. You may also encounter ohm-centimeters when measuring bulk resistivity.

    In these cases and more, a conversion calculator can be a helpful tool to work through the math.

    How do you convert resistivity units?

    Unlike many of the scientific and mathematical concepts found on this site, electric resistivity is usually only measured in ohm-meters.

    However, you can convert ohm-meters into ohm-centimeters and microhm-centimeters.

    Ohm Meter to Ohm Centimeter

    To convert an ohm-meter to an ohm-centimeter, multiply it by 100:

    ohm-centimeter = ohm-meter x 100

    Ohm Meter to Microhm Centimeter

    To get microhm-centimeters, multiply an ohm-meter by 100 million (you'll need a big calculator for this one):

    microhm-centimeter = ohm-meter x 1012

    Do different materials have varying resistivity?

    Different materials do indeed have varying resistivity.

    As we've already mentioned, resistivity is an intrinsic property. Different objects have an immutable resistivity.


    Superconductors have a resistivity of 0 ohm-meters, meaning they are hyper conductive materials.


    A few examples of superconductors are chemical elements like:

    • Mercury or lead.
    • Metal alloys.
    • Different types of ceramics.
    • Organic materials like carbon nanotubes.


    As you might have already assumed, metals are particularly conductive. So they also have a low resistivity at a 10-8 ohm-meters.


    Examples of these kinds of metals are silver, copper, aluminum, and tungsten. These materials get used for computer parts and light bulbs.


    As the name implies, semiconductors are both conductive and resistive. Because of this, these materials are often altered to become more resistive or more conductive.

    This also means that their resistive-ness is variable. They don't have a single ohm-meters measurement.


    Examples of semiconductors are elements found in group 14 of the periodic table. Like silicon and germanium. Certain oxides and alloys are also great semiconductors.


    Electrolytes are solid substances that dissolve in water or another "polar solvent." This creates a conductive solution.

    Because each electrolyte is different and the solvent used for the solution might also be different, the resistivity of electrolytes is also variable.


    Two common examples of electrolyte solutions are Gatorade and Pedialyte. They are both great to drink if electricity isn't currently flowing through them.


    An insulator is a material that has a high resistivity. They prevent electricity from flowing. This class of materials has a resistivity of 1016 ohm-meters.


    Examples of insulators are rubber, plastic, styrofoam, glass, and dry air. This is why you never see lightning unless it's very humid or rainy out.


    Superinsulators are, as the name suggests, insulators that are good at, well, insulating.

    In fact, they have an infinite resistivity. But, superinsulators only exist at extremely low temperatures.


    The only known superinsulator is titanium nitride.

    What is the electrical resistivity formula?

    Resistivity is a simple concept that has a simple formula. But the variables in this formula can be quite hard to quantify.

    Here is the equation for resistivity:

    ϱ = R (A / l)

    In this formula:

    • ϱ equals resistivity, as we've established
    • R is the electrical resistance of a uniform section of the material being measured
    • l is the length of that piece of material
    • A is the cross-sectional area of the object being measured for resistivity

    Resistivity is formulated this way because resistivity is inherent in the properties of a material being measured. This reflects how it works in real life.

    A copper wire, by the cubic unit, is a copper wire.

    It doesn't matter if you bought them from different manufacturers or if they're at a different thickness. They'll have the same resistivities of copper.

    How is resistance different from resistivity?

    When it comes to measuring the conduciveness of an object, there are two properties that are very similar.

    We've already mentioned that resistivity is a measurement of an object's inherent resistivity to electricity, regardless of its size or shape.

    A rubber ball, for example, has higher resistivity than a metal fork.

    But resistance does take into account the size and shape of an object.

    According to Pouillet's Law, "the resistance of a given material increases with length, but decreases with an increased cross-sectional area."

    In other words, an object that is long and thin is more resistant than an object that is short and fat.

    Calculating Resistance

    To calculate resistance, you need to re-arrange the formula for resistivity:

    R = ϱ (l / A)

    Here you'll multiply the resistivity by the length of the material and the area of the cross-section, to determine the total resistance

    Tell your friends about us!