sleeve length ?

so basically , I've bought a jumper and a long sleeve t-shirt , the fit around the chest is good , but the only thing is on both the sleeves are quite long , not so long they touch my fingers but theres a lot of material scrunched up by the elbows ..... in all my clothes I'm normally a size medium .

my question is if i tried a size small , would the sleeve length decrease or are sizes based on chest measurements ??

so basically , I've bought a jumper and a long sleeve t-shirt , the fit around the chest is good , but the only thing is on both the sleeves are quite long , not so long they touch my fingers but theres a lot of material scrunched up by the elbows ..... in all my clothes I'm normally a size medium .

my question is if i tried a size small , would the sleeve length decrease or are sizes based on chest measurements ??

Don't worry about it, I bet it looks fine you can always roll them up a little bit!

The sleeve length will likely decrease very slightly, but probably not so much to make a difference. The difference in the chest measurement will be bigger