Go to Edit > Preferences then to the Add-ons tab. Click Install.

Choose the downloaded zip and click Install Add-on.

After the installation is complete it will show up in the add-on list. Enable the add-on by ticking the checkbox.

Hold ALT and drag with the left mouse button to make a quick measurement without saving. The distance is drawn as a dotted line with a label at the midpoint, in Object Mode and Edit Mode (right mouse button in Edit Mode).

Hold SHIFT + ALT while dragging to save the measurement. Saved measurements are listed in the Measurements panel (N-Panel > Q-Measure tab) and stay visible in the viewport.

Use click-click instead of click-drag for multiple measurements: each additional click starts a new measurement from the previous endpoint. Hold CTRL to enable snapping to vertices, edges and faces.

During a measurement, press X, Y or Z to constrain the endpoint to that axis. Press ESC or right-click to cancel.

Remove the selected measurement with ALT + X, remove all measurements with ALT + CTRL + X, and toggle their display with ALT + SHIFT + X.

The Measurements panel lists every saved measurement with its distance as the label. Select entries to inspect them, and use the remove operator to delete the selected one (or all of them with Shift).

The Hotkeys panel shows the current keymap for every operator, reflecting your active mode (Object or Edit Mode) and any custom keymap changes.

Enable Override to customize the display: active line color, line color, text size, and the unit system (Metric or Imperial) with a fixed length unit (meters, centimeters, feet, inches and more) instead of the scene defaults.