Using maths to calculate chain length? Singlespeed.
 

My chainstay is 16.92 inches, my rear cog has 18 teeth and my front chainring has 42 teeth. Using maths, I can calculate the perfect chain length.

16.92 * 2 = 33.84

18 / 4 = 4.5

42 / 4 = 10.5

33.84 + 4.5 + 10.5 + 1 = 49.84

However, since I am converting to a singlespeed, how does throwing a chain tensioner into the mix affect this calculation? The equation tells me I need 50 links, but if I need to use a chain tensioner, will this be too tight?

Order good amount more than you think you need and remove the excess.

I think you may need to buy some new maths.

Do you mind telling me how kind sir? I used this equation to calculate my current chain length and it works absolutely fine, bike rides perfectly. I'm looking at getting a tensioner because I want to hot swap my chainrings and sprockets on the fly. I'm guessing you know the answer to the question?

There are several websites that can help you. Just google it

I'm not sure I get why the math is needed. Mount the tensioner, Put on the cogs and chainrings you plan to use. Wrap the chain around the cog, tensioner and ring for each application. Break chain to suit and fasten with a quick link (that probably came with your chain). Yes, does require a chain riveter to break the chain. Buy, have a shop do the work or go to a bike coop if you have one.

If money is the issue, try asking for a used, junk chain. Use it to determine the length.

Ben - who's been riding single-speed and fixed for 50 years and has yet to calculate his first chain. In fact, who's never known how many links he's riding.