This calculator allows you to convert between dB and percent (%) values of Error Vector Magnitude.

**How to use the Calculator**

Enter either quantity and the other will be calculated. Note:

- EVM (dB) is a negative value
- EVM (%) is a positive value

**Example EVM Calculation**

An EVM value of 1% translates to -40 dB. As the percent value increases so does the dB value. The maximum is 100% which translates to an EVM of 0 dB.

**What is EVM?**

Error Vector Magnitude is a measure of modulation quality in a communication system. It is the ratio of the average of the error vector power (P_{error}) to the average ideal reference vector power (P_{ref}). Since it is a ratio, it has no units.

**EVM Formula**

**EVM = P _{error}/P_{ref}**

**EVM (dB) = 10*LOG _{10}(P_{error}/P_{ref})**

**EVM (%) = SQRT(P _{error}/P_{ref}) * 100**

**EVM dB vs percentage **

It’s a matter of preference. Some engineers and technologists are used to a logarithmic scale, i.e. dB while others like to see it as a percent value.

**Major Factors that Influence EVM**

Here is a list of impairments that have an influence on EVM:

- IQ mismatch in transmitter and/or receiver
- Frequency offsets
- Phase noise
- AM-AM and AM-PM distortion
- Receiver noise figure
- Multipath fading
- RF interference