Error Vector Magnitude (EVM) dB to Percentage Calculator

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 (Perror) to the average ideal reference vector power (Pref). Since it is a ratio, it has no units.

EVM Formula

EVM = Perror/Pref

EVM (dB) = 10*LOG10(Perror/Pref)

EVM (%) = SQRT(Perror/Pref) * 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

Related Calculators