Originally Posted by Velo Mule

@donnyc you don't have to go out and buy a metric thread gauge. Go to a hardware store and either bring the pedal or buy one M8 x 1.25 bolt. While the diameter is different, the thread pitch is the same. Position the bolt so that the tip of each thread on the bolt drops into the root of each thread on the pedal thread. If they all line up, then indeed, your pitch is 1.25 threads per mm. If they don't line up, find a 1/4" - 20 screw and do the same thing. If this lines up, you have a 20 thread per inch pitch.

I have an imperial size thread gauge, but hardly use it anymore, because this technique is quick and easy.