Abstract A database including results from 102 000 soil analyses was built for arable topsoil in France. We show a strong effect of soil particle-size distribution on present organic carbon (OC) stocks in these soils. By using the upper decile values by textural classes as a proxy of the maximal carbon storage potential, we show that it might be more efficient to encourage practices favouring carbon accumulation in soils already having high OC stocks than to try to increase OC stocks in soils where present stocks are low.