We present flux-calibrated, synthetic spectra for the calibration stars of the Short Wavelength Spectrometer of the Infrared Space Observatory ISO-SWS (cf. Kessler et al. 1996). ISO-SWS covers a wavelength range of 2.4 to 45 μm (cf. de Graauw et al. 1996), and although in the NIR the flux calibration of Vega can be used, at longer wavelengths the flux calibration has to be extrapolated by other means, because (i) Vega has at λ ≥ 25 μm an IR excess due to circumstellar dust and (ii) there is an, as yet, unresolved controversy about Vega's flux at 10 μm (cf. Rieke et al. 1985). The majority of the standard stars of SWS are of MK class G and K III, as cool giants are amongst the brightest objects in the IR, and model atmospheres for cool giants are available and well-studied (cf. Jørgensen and Gustafsson 1994).