TBH I've always been a bit random in working out how long to leave my chain. A quick loose fit round a few rings and sprockets until it looks ok then make the final cut and join.
Thing is if you take out one too many then you're a bit buggered. So there must be a 'proper' way to do this. One were you work it out on a given sprocket or chainring size surely?

round the 2 biggest cogs (miss out the mech) and add one full link (inner and outer plates)

A useful way to tell whether its right is when in big ring/smallest sprocket, the rear mech jockeywheels should line up vertically

That works for me too Mike.

Video on this on Dirt site at the moment…

same as Mike

mike_check – Member
round the 2 biggest cogs (miss out the mech) and add one full link (inner and outer plates

+1

I use the westkipper method

Bear in mind Mikes generally right but there will be some variation needed depending on what length rear derailleur u run and how much rear travel is on the bike

westkipper +1

Thanks for the backup ChrisF, but (coughs modestly), I cant take the credit for that method… it was just a little something that I read on the back of a Shimano cornflake packet. 😉