You're in a low stakes MTT and still far away from the bubble.

You have a pocket pair, 7s

Early positions fold and middle position shoves all in and he has exactly as many chips as you. You are new, just got moved to the table, and you have no reads.

Everyone folds and the action is to you.

What is the maximum stack size you are willing to make a call with?

I'd only be calling with <10bb

Cue chants of nit

I'm calling off around 15 or so bbs.

It depends on, how many players are left to act. The more people left to act, the higher the risk of getting ambushed by someone waking up with a bigger pair behind us.

Sorry, I meant to say that you are on the big blind and last to act. If so, what do you think?

Probably up to 15BB is my answer offhand, although I'd have to think about it and do the math to get a more solid answer. The shorter villain is, the more likely you'll see worse pairs and Ax hands with x < 7. From 15-20BB I think you might see shoves from 88-99 and hands you flip with but not necessarily 66. Or maybe 66 but not any lower pairs, and more higher ones than lower ones, so probably a fold.

Then I agree with up to 15BB, as others have suggested. If we are far from the money, the tournament average is likely around 30-40BB, so the player jamming could be a little desperate, and we really need a dubble, so we dont mind "flipping" with two overcards. However if they are jamming more than 15BB, then we need to ask, why they are not minraising, which would be a more normal play. And unless they are just bad, it typically mean a fairly specific range, that dont include the biggest pocket pairs, but it also dont include many hands with cards lower than a 7. Maybe something like 66-JJ and AQ-AK, and against that kind of range we need at least 99 to make a profitable call.