Umbrella Measurements

I have a very simple question to ask of you knowledgeable people. Are the measurements of umbrellas the Radius or the Diameter of the umbrella? I'm assuming that it's the Diameter, but I'm not exactly sure. The reason I ask is because I plan on getting some basic lighting equipment for this little number, and I want to make sure that I'm getting the right umbrella size. The distance from my shoulder to the palm of my hand is about 25 1/2", so going by that, I think that I need a 25-27" umbrella for this setup. But as I previously stated, I don't know if the measurement is in Radius or Diameter. BTW, I plan on using a hot shoe sync cord for this, as it's a hell of a lot cheaper than using Canons wireless solution.

Simple question with a simple answer, so which is it?

Diameter certainly...could you imagine the room size needed to support a 36" or 48" radius?!
http://www.bonanzle.co​m …nsparent_Umbrel​la_48_inch

So I could even get away with hand holding a 50" umbrella then?

Gerald3 wrote in post #10348841
So I could even get away with hand holding a 50" umbrella then?

Unless you are walking in the rain, or shielding yourself from the sun, or serving as an assistant to someone else who is the photographer, hand holding any umbrella is only going to distract you from composing and holding the camera steady while you shoot!

Well in that case, I'll just mount the umbrella and flash on my tripod with an adapter. Thanks for the info, I'm new to external flash lighting. I've been reading this article over the past few days and it's been very helpful and informative.