We present the Exposure Time Calculator of IGRINS (Immersion Grating Infrared Spectrograph). The noises of IGRINS and the simulated emission line 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. In case of calculation of noises, the user needs to input the expected target magnitude, the weather conditions, and the desired exposure time. In addition to the simulated emission line, the parameters of rest wavelength, line-flux, Doppler shift and line-width are needed. The output would be the expected signal-to-noise for each spectral resolution element. The source-code of IGRINS-ETC v2.1.1 is available to be downloaded on the World Wide Web.