We present the Exposure Time Calculator of IGRINS. The noises of IGRINS can be calculated from the combination of Telluric background emission and absorptions, the emission and transmission of the telescope and instrument optics, and the dark noise and the read noise of the infrared arrays. For the atmospheric transmissions, we apply the simulated spectra depending on the Precipitable Water Vapor (PWV) values. The user needs to input the expected target magnitude, the weather conditions, and the desired exposure time. The output would be the expected signal-to-noise for each spectral resolution element.