There used to be a calculator in the modeler-only tools in QGIS graphical modeler. But I notice that it is missing in QGIS3. How do I do numerical calculations as part of the model? For example, take input in km and convert it to meters for certain algorithm.

1 Answer 1


You can use expression within a model. For instance, my distance is in kilometers. But I want to do my buffer with meters.

Next to the distance field in the buffer algorithm, you can choose an expression input. And then use the number input with a formula.

model with expression

  • Thanks. Exactly what I was looking for. Being able to use the expression within the model removes the need for a separate calculator algorithm and is much more powerful. Feb 22, 2019 at 17:27

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