Abstract Data of soil organic matter (SOM) content can be used for the assessment of stocks and changes of soil organic carbon (SOC) in peatland soils. Therefore, it is essentially necessary to convert SOM contents into SOC contents by SOM/SOC ratios (“conversion factors”). Various substrates of peatland soils in Northeastern Germany (n = 311) were analyzed in SOM/SOC ratios. Sphagnum peats showed significantly higher SOM/SOC ratios (2.05 ± 0.09) than peats of vascular plants (1.73 ± 0.09) and amorphous peats (1.93 ± 0.29). Amorphous peats and humic sands (2.41 ± 0.46) showed a high variability. The classification using WRB qualifiers featured significant differences (***P