Provided is an organic light emitting display including a display panel, a data driver supplying a data signal to the display panel, a timing controller controlling the data driver, a power source supply unit converting an external voltage and outputting a high potential voltage and a low potential voltage through a first power source line and a second power source line, a measurement unit measuring a current or a voltage flowing through the first power source line and the second power source line and outputting a measured value, and a compensation coefficient calculator matching the measured value and a reference value stored in the compensation coefficient calculator to a driving signal and comparing the measured value and the reference value to judge a degree of noise and calculating a compensation coefficient.