I have2 box fans and a laptop using a 15 amp breaker.. will those three things throw a 15 amp breaker?

Probably... but you need to know the watts each uses to calculate how much the load really is... you add all the wattage together... take that number use Ohms law to find the amps... and you will see how close to the 15 amps you actually are.

But honestly I don't think you will have a problem.

Unless they are huge fans, you will never get near 15 Amps. However, what else is on the circuit?

And by circuit.. as ma0641 mentions... more than one outlet are usually daisy chained... meaning there might be far more on it than you think.

I recommend the "bull force" method, turn them on and try it...
If it trips you have your answer... if you need to, reset the breaker... no cost...

I have2 box fans and a laptop using a 15 amp breaker.. will those three things throw a 15 amp breaker?
I can tell you with 100% certainty these three things together will not trip a 15A breaker by themselves. Not even remotely close.