Chromosome-scale genome assembly is affected by scaffolding errors and may yield incorrect chromosome sizes. Today, we present KICS, a semi-automated and cost-efficient approach for examining the validity of the assembly by estimating relative chromosome sizes from the respective karyotype images. The method employs threshold-based image segmentation and uses the extracted chromosome areas as proxies for the actual chromosome sizes. The suitability of the approach is confirmed by a strong correlation between area and DNA content evaluated on karyotype images of varied species and achieving a 6 Mb chromosome size error on a reference human karyotype dataset.