diff --git a/python/plugins/processing/algs/qgis/IdwInterpolation.py b/python/plugins/processing/algs/qgis/IdwInterpolation.py
index 0d8d7d47b52e..d2f9f0204560 100644
--- a/python/plugins/processing/algs/qgis/IdwInterpolation.py
+++ b/python/plugins/processing/algs/qgis/IdwInterpolation.py
@@ -33,6 +33,7 @@
                        QgsProcessingUtils,
                        QgsProcessingParameterNumber,
                        QgsProcessingParameterExtent,
+                       QgsProcessingParameterDefinition,
                        QgsProcessingParameterRasterDestination,
                        QgsProcessingException)
 from qgis.analysis import (QgsInterpolator,
@@ -50,6 +51,8 @@ class IdwInterpolation(QgisAlgorithm):
     INTERPOLATION_DATA = 'INTERPOLATION_DATA'
     DISTANCE_COEFFICIENT = 'DISTANCE_COEFFICIENT'
     PIXEL_SIZE = 'PIXEL_SIZE'
+    COLUMNS = 'COLUMNS'
+    ROWS = 'ROWS'
     EXTENT = 'EXTENT'
     OUTPUT = 'OUTPUT'
 
@@ -83,6 +86,20 @@ def initAlgorithm(self, config=None):
                                               default=0.1)
         self.addParameter(pixel_size_param)
 
+        cols_param = QgsProcessingParameterNumber(self.COLUMNS,
+                                                  self.tr('Number of columns'),
+                                                  optional=True,
+                                                  minValue=0, maxValue=10000000)
+        cols_param.setFlags(cols_param.flags() | QgsProcessingParameterDefinition.FlagHidden)
+        self.addParameter(cols_param)
+
+        rows_param = QgsProcessingParameterNumber(self.ROWS,
+                                                  self.tr('Number of rows'),
+                                                  optional=True,
+                                                  minValue=0, maxValue=10000000)
+        rows_param.setFlags(rows_param.flags() | QgsProcessingParameterDefinition.FlagHidden)
+        self.addParameter(rows_param)
+
         self.addParameter(QgsProcessingParameterRasterDestination(self.OUTPUT,
                                                                   self.tr('Interpolated')))
 
@@ -99,6 +116,13 @@ def processAlgorithm(self, parameters, context, feedback):
         pixel_size = self.parameterAsDouble(parameters, self.PIXEL_SIZE, context)
         output = self.parameterAsOutputLayer(parameters, self.OUTPUT, context)
 
+        columns = self.parameterAsInt(parameters, self.COLUMNS, context)
+        rows = self.parameterAsInt(parameters, self.ROWS, context)
+        if columns == 0:
+            columns = max(round(bbox.width() / pixel_size) + 1, 1)
+        if rows == 0:
+            rows = max(round(bbox.height() / pixel_size) + 1, 1)
+
         if interpolationData is None:
             raise QgsProcessingException(
                 self.tr('You need to specify at least one input layer.'))
@@ -127,9 +151,6 @@ def processAlgorithm(self, parameters, context, feedback):
         interpolator = QgsIDWInterpolator(layerData)
         interpolator.setDistanceCoefficient(coefficient)
 
-        rows = max(round(bbox.height() / pixel_size) + 1, 1)
-        columns = max(round(bbox.width() / pixel_size) + 1, 1)
-
         writer = QgsGridFileWriter(interpolator,
                                    output,
                                    bbox,
diff --git a/python/plugins/processing/algs/qgis/TinInterpolation.py b/python/plugins/processing/algs/qgis/TinInterpolation.py
index 3fba278c4adf..f215ad15d123 100644
--- a/python/plugins/processing/algs/qgis/TinInterpolation.py
+++ b/python/plugins/processing/algs/qgis/TinInterpolation.py
@@ -34,6 +34,7 @@
                        QgsProcessingParameterEnum,
                        QgsProcessingParameterNumber,
                        QgsProcessingParameterExtent,
+                       QgsProcessingParameterDefinition,
                        QgsProcessingParameterRasterDestination,
                        QgsWkbTypes,
                        QgsProcessingParameterFeatureSink,
@@ -53,6 +54,8 @@ class TinInterpolation(QgisAlgorithm):
     INTERPOLATION_DATA = 'INTERPOLATION_DATA'
     METHOD = 'METHOD'
     PIXEL_SIZE = 'PIXEL_SIZE'
+    COLUMNS = 'COLUMNS'
+    ROWS = 'ROWS'
     EXTENT = 'EXTENT'
     OUTPUT = 'OUTPUT'
     TRIANGULATION = 'TRIANGULATION'
@@ -91,6 +94,20 @@ def initAlgorithm(self, config=None):
                                               default=0.1)
         self.addParameter(pixel_size_param)
 
+        cols_param = QgsProcessingParameterNumber(self.COLUMNS,
+                                                  self.tr('Number of columns'),
+                                                  optional=True,
+                                                  minValue=0, maxValue=10000000)
+        cols_param.setFlags(cols_param.flags() | QgsProcessingParameterDefinition.FlagHidden)
+        self.addParameter(cols_param)
+
+        rows_param = QgsProcessingParameterNumber(self.ROWS,
+                                                  self.tr('Number of rows'),
+                                                  optional=True,
+                                                  minValue=0, maxValue=10000000)
+        rows_param.setFlags(rows_param.flags() | QgsProcessingParameterDefinition.FlagHidden)
+        self.addParameter(rows_param)
+
         self.addParameter(QgsProcessingParameterRasterDestination(self.OUTPUT,
                                                                   self.tr('Interpolated')))
 
@@ -114,6 +131,13 @@ def processAlgorithm(self, parameters, context, feedback):
         pixel_size = self.parameterAsDouble(parameters, self.PIXEL_SIZE, context)
         output = self.parameterAsOutputLayer(parameters, self.OUTPUT, context)
 
+        columns = self.parameterAsInt(parameters, self.COLUMNS, context)
+        rows = self.parameterAsInt(parameters, self.ROWS, context)
+        if columns == 0:
+            columns = max(round(bbox.width() / pixel_size) + 1, 1)
+        if rows == 0:
+            rows = max(round(bbox.height() / pixel_size) + 1, 1)
+
         if interpolationData is None:
             raise QgsProcessingException(
                 self.tr('You need to specify at least one input layer.'))
@@ -154,9 +178,6 @@ def processAlgorithm(self, parameters, context, feedback):
         if triangulation_sink is not None:
             interpolator.setTriangulationSink(triangulation_sink)
 
-        rows = max(round(bbox.height() / pixel_size) + 1, 1)
-        columns = max(round(bbox.width() / pixel_size) + 1, 1)
-
         writer = QgsGridFileWriter(interpolator,
                                    output,
                                    bbox,