Measure Pro

On-screen ruler for iPhone and iPad

The Ruler tool draws a real-size ruler across your whole screen, with graduations down both edges. Lay a small object on the glass and drag the rust lines to its ends to read its size. For something longer than the phone, slide the phone down to the mark and carry on: the reading keeps counting from zero.

How to use it

1. Choose Ruler in the tool strip. It fills the whole screen.
2. Lay the object against either edge of the screen.
3. Drag the two handles to the ends of the object and read the size at the top.
4. For longer things, slide the phone down to where the object reaches and scroll on. The total keeps counting.

Good for

• Screws, coins, buttons, jewellery and other small parts
• Checking a printout or a drawing at real size

What it can’t do

• iOS doesn’t tell apps the physical size of the screen, so the app keeps a table of every iPhone and iPad screen. On a model it doesn’t recognise yet, it uses a typical value and can be a few percent out.
• For long objects, the result depends on how carefully you slide the phone.