EVM ↔ SNR Converter
Converts between error vector magnitude (EVM) and signal-to-noise ratio (equivalently MER) for a digitally modulated carrier. Enter either an EVM or an SNR and press Calculate; the other is computed, along with the densest QAM constellation the link can support. This assumes EVM is dominated by additive noise (it also captures phase noise, distortion and I/Q errors in practice, which only lower the achievable order).
Equations & Parameters ▸
\(\text{EVM}_{\text{rms}} = 10^{-\text{SNR}/20} \qquad \text{SNR (dB)} = -20\log_{10}\text{EVM}_{\text{rms}}\)
\(\text{EVM (dB)} = 20\log_{10}\text{EVM}_{\text{rms}} = -\text{SNR (dB)}\)
\(\text{EVM (dB)} = 20\log_{10}\text{EVM}_{\text{rms}} = -\text{SNR (dB)}\)
| EVM | RMS error vector magnitude, as a percentage of the reference constellation's RMS amplitude. |
| SNR / MER | Signal-to-noise ratio (dB). For an ideal reference constellation the modulation error ratio (MER) equals the SNR. |
| Max QAM | Densest constellation whose typical EVM limit (approx. 3GPP) is met by this EVM. |
References: M. D. McKinley et al., "EVM calculation for broadband modulated signals," 64th ARFTG Conf., 2004. · 3GPP TS 38.104 (NR base-station EVM requirements).
Inputs
%
RMS, % of referencedB
Equivalent SNRResults
Converted
EVM (rms)—
EVM (dB)—
SNR / MER—
Link capability
Suggested max QAM—
Diagram