Field Calculator in QGIS II Function in Field Calculator II Field Calculator use in QGIS II QGIS

A short example illustrates how field calculator works when using the Expression tab. We want to calculate the length in km of the railroads layer from the QGIS sample dataset:

Click on toggleEditing Toggle editing mode and open the calculateField Field Calculator dialog.
Select the checkbox Create a new field checkbox to save the calculations into a new field.
Add length as Output field name and real as Output field type, and define Output field width to be 10 and Precision, 3.
Now double click on function $length in the Geometry group to add it into the Field calculator expression box.
Complete the expression by typing ‘’/ 1000’’ in the Field calculator expression box and click [Ok].
You can now find a new field length in the attribute table.