# Illustrator CS4 - how to find out the radius of rounded rectangle corners?

Is it possible to somehow find out the value of radius of rounded rectangle corners in Illustrator CS4? I know one could just click with Rounded Rectangle tool after drawing the rectangle to display the last used value of the radius but what if it is an old document with many different rounded rectangles?

It is basically the same question as this one, but this time the question is about AI CS4 - not Photoshop.

You can use the exact same technique as the linked question. You just measure the difference in point positions.

If you are working in pixels, turn on pixel preview (View -> Pixel Preview) and count the number of pixels rows from one point to the next.

If you are working in any other units, just calculate the difference in the points X/Y position. You can see a points position in the Transform panel. You can see in the example the Y position of the points are 140pt and 150pt. The difference between those points is 10pt = the corner radius you are looking for is 10pt.

• Nice, this is a very easy way to find out the radius of just about anything in Illustrator. – Alin Mar 4 '16 at 8:34
• That solved my problem, the results are good enough but sometimes not perfect. For the example when working in mm units the calculated radius was 5.292 mm when by clicking with the Rounded Rectangle tool after drawing the rectangle I can see the more precise number (5.2917 mm). In that case switching to pixels in most cases allows better precision but it depends. – Chupo_cro Mar 4 '16 at 13:18
• I would say the rounded rectangle tool is what wasn't accurate, not the existing point positions. I'm sure an error margin of 0.003mm is probably acceptable either way though ;) – Cai Mar 4 '16 at 13:21
• Yes, the precision is not problem. But all objects with the same rounding radius should have exactly the same radius parameter rather than 'almost the same'. I can imagine someone might want to parse the .ai file to extract all objects with certain parameters and if the parameters are only approximations then the same looking objects would have the range of radius parameter instead of just one value. – Chupo_cro Mar 4 '16 at 14:49
• Easy fix would be if selecting the rounded rectangle would copy its parameters into the 'last used values' buffer so clicking with the Rounded Rectangle tool would display parameters of the last selected rectangle rather than the last drawn one. – Chupo_cro Mar 4 '16 at 14:49