Rainfall erosivity (R-factor) is an important variable used in soil erosion estimation models. In Costa Rica, the R-factor was computed for 106 stations across the country by Wilhelm-Günther Vahrson in 1990. These results provided the main input information for this study, which used them to estimate the R-factor for Costa Rica. Regression equations were computed to estimate the R-factor for the Caribbean slope, the Pacific slope, and the country as a whole. Forward stepwise analysis and multiple regression analysis were employed to determine the regression coefficients for each developed equation. Elevation and monthly rainfall had a strong influence on the definition of the R-factor equations. The Modified Fournier Index variable was included only in the national-scale equation as a good proxy for the mean annual precipitation effect at each site. Inclusion of elevation in all equations reflects the importance of the transitional effect of high-intensity convective rainfall in the lowlands and low-intensity orographic rainfall in the highlands. This study provides an easy way to estimate the R-factor using regression equations that require only simple and readily available geophysical information. The use of these equations in conjunction with soil and land-use maps as well as digital elevation models will allow the estimation and evaluation of soil erosion on a watershed scale in Costa Rica. This will also improve the application of other hydrological models that require soil erosion as an input variable to estimate sediment yields. © 2014 by the authors.