Where can I get my ring size?

Another random one!
I want to buy some rings, but I have no clue of my ring size! I'd like to find out, but is there a place I can do that without feeling obliged to buy something? I'd feel a bit rude asking them to measure and then leaving~

Thanks!

Ring stores are a good place to start!

You can print out your own ring sizer from the inter web. Such as this one
http://www.lumeradiamonds.com/files/ring_sizer.pdf
And convert to Japanese sizes from the table here
http://en.wikipedia.org/wiki/Ring_size
or use a piece of string, measure with a ruler and compare to a sizing chart.