Quantitative knowledge of infrared absorption by water vapor is crucial for remote sensing and climate simulations. Near-infrared (NIR) continuum absorption currently still lacks quantification by atmospheric measurements but can be investigated with radiative closure experiments using radiometrically calibrated solar spectra. We demonstrate for the first time a calibration method with sufficient accuracy (1.0–1.7 %) for continuum quantification in the 2500 to 7800 cm⁻¹spectral range.