Question about chain length

[Jerry845]

Hi I have bike called specialized secteur 2013
Did on it 4500 miles and wanted to replace a few parts. Chainring, cassette and chain

I replaced cassette from 12-25 to 11-28, chainring will stay the same I mean 50t. And new chain kmc x9

Can someone please tell me how long chain should be for 11-28 cassette and 50t chainring?

Rear Derralieur is standard sora.


Thanks

[cny-man]

There are several methods, can't go just by number of teeth. Google "bicycle chain length" and take your pick.