In this paper, we present a technique to enable accurate built-in measurement of EVM for OFDM transceivers. This measurement technique only relies on the decoded bit pattern, and does not require any additional test equipment. In order to accurately predict EVM without using analog signal analysis, we intentionally code more symbols into the bit pattern in test mode, which enables the decoding of IQ signals in finer granularity. We present an innovative DFT technique to measure EVM on-chip with very little overhead. We also provide an analytical framework to determine how the DFT technique needs to be implemented. Experimental results using MATLAB simulations and hardware measurements confirm the accuracy of the proposed technique.