If you’re looking through an **inductor kit** to find the right option for your circuit, it’s important to double-check the numbers and colour markers on the component itself. Often, an inductor will have three digits on its surface. To work out the inductance in microhenries (uH), the first two digits should be multiplied by the third digit to the power of 10.

For example, if the code said 233, the calculation would be:

**23 x 10^3 = 23,000 uH (23mH)**

If there’s the letter ‘R’ in between two digits, this indicates a decimal point. E.g., 7R2 = 7.2 uH. Another letter, such as u, n, or p, will indicate a different unit of inductance such as N equals nano-henry.

Then, if there’s a fourth digit at the end of the code, this will indicate the tolerance of the inductor, with B equalling the lowest and N the highest. Plus, in some cases, there may be colour codes on the inductor rather than numbers and letters, with the first and second being the value number and the third indicating the multiplier you need to use to get the inductance value. If there’s a fourth, this will indicate the tolerance of the inductor by percentage. Checking a colour code chart will help you to find the final values.

Though this code gives you the value of inductance (how much energy can be stored by the inductor) to measure its impedance (how much energy it is resisting), you then need to use the calculation below (where f is the frequency in Hertz of the current passing through the inductor and L is the component’s inductance in Henries).

**XL = 2πƒL**