Std UnitsCalculator

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Std UnitsCalculator.svg Std UnitsCalculator

Menu location
Tools → Units calculator...
Default shortcut
Introduced in version
See also


The Std UnitsCalculator command opens the Units calculator dialog box. The Units calculator can be used to convert values from one units system to another.

Units Calculator it.png

The Units calculator dialog box


  1. Select the Tools → Std UnitsCalculator.svg Units calculator... option from the menu.
  2. The Units calculator dialog box pops up.
  3. For more information see Options.
  4. The dialog box is modeless, meaning it can stay open while you continue working in FreeCAD.
  5. Press the Close button to close the dialog box.


Top row

  1. Enter a value with units in the first input box. For example 10 mm.
    • Units with exponents should be entered using the ^ notation. For example 1 m^2.
    • If the input value cannot be recognized or the units are unknown the => box will display the 'syntax error' message.
  2. Enter the target units in the second input box. For example in.
    • If the units are unknown the => box will display the 'unknown unit' message.
    • If the units in the first and second input box do not match, the => box will display the 'unit mismatch' message. In the example the units match as 'mm' and 'in' are both length units.
  3. If there are no input errors the => box will immediately show the result. For the example values the result is 0,394 in.
  4. Optionally press the Copy button to copy the content of the => box to the clipboard. The value can then for example be pasted in a FreeCAD task panel or dialog box.

Text area

  1. The conversion performed in the top row can be copied to the text area by pressing Enter in the first or second input box.
  2. The text area can contain multiple conversions and its content can be selected and copied to the clipboard with Ctrl+C and used in other programs.


This new part of the Units calculator still suffers from some bugs. introduced in version 0.19

  1. Select an option from the Unit system dropdown list. This will be the target unit system. Select 'Preference system' to use the unit system defined in the Preferences.
  2. Select an option from the Unit category dropdown list.
  3. Enter a value with units in the Quantity input box. The units must match the unit category.
    • If the 'Area' unit category has been selected entering certain units is problematic. For example to enter m^2 you have to first enter ^2, put the cursor before the ^ character and then enter m.
  4. Click in the Decimals input box and press Enter to convert the value in the Quantity input box.
  5. Changing the value in the Decimals input box has no effect on the calculations. The number of decimals defined in the Preferences is always used instead.


  • See the Expressions page for a list of all known units.