You can add, edit, show, and delete dimensions; you can also specify how dimensions appear.
If you are new to Inventor we recommend looking over the Getting Started and Guided Tutorials that pertain to sketches.
Brief video of creating sketch dimensions
In a sketch, click Sketch tab
Constrain panel
Dimension
(2D sketch) or 3D Sketch tab
Constrain panel
Dimension
(3D sketch).
In the graphics window, click the geometry that you want to dimension and then click to place the dimension.
In a 3D sketch, the dimension text is parallel to a plane created by the two selections.
Continue selecting geometry to create additional dimensions, or right-click and choose OK.
In a 3D sketch, you can enable or disable adding dimensions to geometry as you sketch. Click Dynamic Dimension in the status bar to enable or disable the ability to add dimensions in the value box as you sketch. You can also press Ctrl + D to toggle Dynamic Dimension on or off.
In a sketch, to edit a dimension do either of the following:
In the Edit Dimension dialog box, do any of the following:
Click the check mark to accept the new dimension.
To reposition dimension text, pause the cursor over the text, when you see the move cursor
, click-drag the dimension to a new position.
Make dimensions visible so you can edit them.
Right-click a feature in the browser or graphics window and choose Show Dimensions.
Right-click a sketch in the browser and toggle on Dimension Visibility.
Select View Tab, Visibility panel, Object Visibility, and select or deselect the Sketch Dimensions check box to show or hide all sketch dimensions.
Double click the sketch node in the browser to edit the sketch.

In an active sketch, choose one of the dimension display icons in the status bar:
A driven dimension is a reference parameter that reports a measurement value for the associated geometry. It does not define or drive the geometry and therefore cannot be directly edited. Driven dimensions are created in two ways, by:
Only normal dimensions can be manually edited. Convert driven dimensions to normal dimensions so you can edit them.
In a fully-constrained sketch, you must first convert one or more regular dimensions to driven (reference) dimensions, or remove some dimensions or constraints, before you can convert driven dimensions to normal dimensions.
To convert a driven dimension to a normal dimension:
In the sketch, make sure the geometry is not fully constrained. Fully constrained geometry displays with a different color than under-constrained geometry.
Select the driven dimension or dimensions that you want to convert.
Click Sketch tab
Format panel > Driven Dimension
(2D sketches) or 3D Sketch tab
Format panel
Driven Dimension
(3D sketches) to deselect it and make the dimension or dimensions normal.