There is a need for improved soil texture maps in Swedish arable soils. Clay is normally not analyzed in traditional soil mapping carried out by the farmers in Sweden, and only very general soil texture information is available for national and regional modeling of leaching in arable land. The goal of this project was to evaluate the use of gamma-ray spectrometry for rapid mapping of soil clay, both at the regional scale and locally within fields. We used already available, extensive gamma-ray data acquired by airplane in an area of 120,000 ha of arable land in southwest Sweden, as well as detailed data at six project farms collected by an equipment (The Mole, the Soil Company, the Netherlands) mounted on quad-bike. Using only 75 calibration points distributed at five of the project farms, a regional map of soil clay concentration was produced from the airborne gamma data. It was compared against 1411 validation samples obtained at 36 other farms (R² = 0.68, RMSEP = 7.16 and RPD = 1.77). The vehicle-based gamma-ray equipment was used at the field level. A regional calibration model was tested at two fields with 98 validation samples in each field (Farm One: R² = 0.58, RMSEP = 3.83 and RPD = 1.54; Farm Two: R² = 0.74, RMSEP = 2.81 and RPD = 1.97). In conclusion, even with a very limited number of calibration samples, gamma-ray spectrometry can be used for efficient soil clay mapping in this type of landscape, both at the regional scale and within fields.