Chainring diameter calculation

[p nut]

I am looking to get a larger chainring for my cross bike. It's a 1x set up. I'd like to see if I can fit a 50T on there. Currently, I've got a 42T.

In order the figure out the clearance, I'm wondering if I can get a good idea by figuring out the diameter of the chainring to see if it would make contact with the chainstay. I didn't want to drop $60-80 only to find out it doesn't fit.

Thanks.

[PacNW2Ford]

It’s roughly 8” diameter for a 50t. A chain is 1/2” pitch, 50*0.5=25”, then divide by pi and you get ~8”. Your 42t is 6.7”, so the 50 will extend out about 0.64” or 5/8”.

[Louis]

Another way to do it:

At this number of teeth, the radii should be about linearly proportional to the number of teeth, so the new radius would be just about 50 / 42 = 1.190 x the old one.

Sanity check on PacNW2Ford's numbers: 8 / 6.7 = 1.194, so just about the same thing.

[HTupolev]

Each tooth adds about 2.02mm to the radius of a chainring.

[p nut]

Thanks Gents! I think it should barely clear! Hope