Bits!!

How can you tell when a bit is too small, or does not fit correctly?!

If the bit is too small, it will pinch the corners of the horse's mouth. You should be able to fit a finger between the bit ring and the corner of the horse's mouth. This differs slightly between bit types, but basically you don't want to rings to be pressing right into the mouth.

Thank you it just when I put the bit in my horses mouth it is already pulling his mouth up or back when the reins are loose.... the bit looks like this snaffle

That sounds more like an issue with how the bridle is adjusted, not the bit. Try putting the bit hangers (the strap on the bridle that the bit is attached to) on a lower hole and see if it fits better.

i will try but that seems like what the problem is.....just wondering he is using I think they call it loose ring snaffle and does not really respond to it... do you or any one knows what is a better one for him??

I agree with the others..I would look to adjust the bridle.

I wouldn't try a new bit, I would just work on getting him to respond to the loose ring.

A loose ring snaffle was designed as a 'drag and pull' bit. You pull the reins and horse comes to you. Or you drag the rein and the horse gives to bit pressure. It is designed to teach a horse to turn or move in the direction of the pull.
Like driving horses for example. Or in riding horses, to teach a horse how to turn and give to bit pressure. That's it.
Once a horse knows how to do that then it's best to put them in a bit that will teach them more like lateral flexion etc...
You have no ability to lift a shoulder in a loose ring bit.

Perhaps the horse is telling you that he/she is ready for a different bit.

IMHO, if the horse won't respond the way you want to a simple snaffle, then they are certainly not ready to move up to the more advanced bits.

OP, do you have a picture of the way that the bit/bridle is fitting the horse. I agree with others that it sounds like the bridle is too tight but we can't be sure unless we can see exactly what you're talking about.