Aequo: On-Screen Measurements

A lightweight utility designed to help you take length and angle measurements of objects on your screen.


Does very simply what others can’t usually, draw from any pixel to any other pixel and give the distance no matter the angle. In addition it keeps the results for you. I asked if he could add a way to vary the shaded screen you had to work through and he immediately added that option so it works much better now with better visabilty of the object being measured.

A very versatile tool to quickly take measurements on photos, videos, or anything else.

I found this simple app very useful when sizing images that are odd shapped in a Word document. I used to put a physical ruler onto my screen (sounds crazy I know, but it did work). This app makes it easy.



Inch GridAdd a grid overlay with major grid lines every inch and minor grid lines every eighth of an inch⌘G
Centimeter GridAdd a grid overlay with major grid lines every centimeter and minor grid lines every millimeter⇧⌘G
ProtractorDisplay a protractor. Move the protractor around the screen by clicking and dragging, scale it up or down by scrolling, and rotate it by holding option (⌥) and scrolling.⌘P
Linear Measure ToolClick once to start a linear measurement at the reticle; click again to complete the measurement⌘L
Slope ToolSelect any two existing linear measurements with the reticle to find their slopes and an angle between them⌘I
Live AnglesToggle whether angles between existing and in-progress linear measurements are shown⌥⌘L
Linear Conversion FactorSupply a ratio between a real-world distance and an on-screen one (say, via a ruler in a photo) to automatically convert linear measurements⇧⌘L
Angle Measure ToolClick once to define the vertex of an angle at the reticle, again to set a second point, and a third time to complete the angle⌘N
Keep Past MeasurementsToggle whether past measurements are cleared before starting another one⇧⌘K
HistoryShow a copy-able log of all measurements made in the current session⇧⌘H
Undo/RedoUndo or repeat past measurements (to remove annotations made with the Pen, the Eraser can be used instead)⌘Z / ⇧⌘Z
Pen ToolUse your cursor to draw free-form in the Aequo window⌘D
Eraser ToolErase strokes made with the Pen Tool only (not measurements)⌘E
Pen ColorChange the stroke color of the Pen Tool⌘1⌘8
Clear MenuClear past measurement history, linear or angle measurements, annotations, or everything in the Aequo windowN/A
Offset Cursor CrosshairsToggle whether the measurement reticle is located at the cursor, or offset north-west slightly⇧⌘C
Toggle Background ContrastChoose whether the Aequo overlay has a light or dark tint (e.g., to provide better contrast with the screen underneath the window)⇧⌘B
Increase Window TransparencyIncrease transparency of the main window in steps of 10%⇧⌘=
Decrease Window TransparencyDecrease transparency of the main window in steps of 10%⇧⌘-

Other Tips

Aequo for Education

Teachers or educational institutions can get a 50% discount by using the App Store Volume Purchase Program. Visit to learn more.