This tool allows you to calculate the Root mean square value of EVM to its dB equivalent. It also computes the dB value from RMS.
EVMRMS = 100 * 10^(EVMdB/20)
EVMdB = 20 * LOG10^(EVMRMS/100)
How to use the calculator
EVM is a measure of modulation quality of a communication system. Enter a number in either field of the tool. The dB value should be a negative number lower than zero. The percent value should be a number between 0 and 100.
The lower the value of EVM either in percentage or dB, the lower the error. This translates directly to lower Bit error rate and higher quality signals.
A value of -40 dB translates to 1% EVM.
What is a good value of EVM?
The answer depends on the modulation format and target performance levels. For 802.11 Wi-Fi systems, the IEEE for instance requires -30 dB EVM for 256 QAM modulation and coding rate of 3/4. As the modulation constellation size increases from 256 to higher, the target EVM becomes lower.