diff --git a/python/plugins/processing/algs/qgis/RasterCalculator.py b/python/plugins/processing/algs/qgis/RasterCalculator.py
index 82c4023c644..7055bc4fae0 100644
--- a/python/plugins/processing/algs/qgis/RasterCalculator.py
+++ b/python/plugins/processing/algs/qgis/RasterCalculator.py
@@ -168,8 +168,8 @@ class RasterCalculator(QgisAlgorithm):
 
         output = self.parameterAsOutputLayer(parameters, self.OUTPUT, context)
 
-        width = math.floor((bbox.xMaximum() - bbox.xMinimum()) / cellsize)
-        height = math.floor((bbox.yMaximum() - bbox.yMinimum()) / cellsize)
+        width = round((bbox.xMaximum() - bbox.xMinimum()) / cellsize)
+        height = round((bbox.yMaximum() - bbox.yMinimum()) / cellsize)
         driverName = GdalUtils.getFormatShortNameFromFilename(output)
 
         calc = QgsRasterCalculator(expression,