Should I get a medium or small t-shirt?

anyone..?

Take your waist and chest measures with a tape measure. Then use the sizing chart. The length shouldn’t be a problem because you are still short.

Sizing tends to vary from company to company. The easiest way to decide is to try the t-shirt on. If you have an American Apparel near you could try on a couple of their basic T’s and decide what size you are.

Sounds like a Small to me, but you should follow the sizing chart and how to measure guide on the site.

Chest – 30 inches
Waist – 27 inches
Which on American Apparel is XXS. That doesn’t seem right.

Small.

Only a teenager could make an existential crisis out of a t-shirt size.
Small.

Or for variety, a boy’s Large?

Which MysteryGuitarMan shirt should I get?

http://www.districtlines.com/21532-Mystery-Guitar-Man-Blue-on-White-T-Shirt/Mystery-Guitar-Man

http://www.districtlines.com/24478-Retro-Black-T-Shirt/Mystery-Guitar-Man

http://www.districtlines.com/24795-Joe-Holding-Joe-T-Shirt/Mystery-Guitar-Man

You could try a medium/ long. Depending on the garment there will be some shrinkage from laundering.

It’s a shirt. Try it on.

@zen I can’t. I’m buying online.

Look at the male members of your family and ask when they got their growth spurt and how tall they got. You’re fifteen; you’re not going to stay the same height. I say get the larger one.
As @woodcutter said, T-shirts may shrink.
I think you should choose your own shirt. It’s going to say something about you and only you know what message is right for you.
Oh, and welcome to Fluther!

Get a small. That site’s shirts run long.

I fit a size small shirt and I am over half a foot taller than you and weight about 60 pounds more than you. You’ll be ok. Let’s consider this one settled.