guitarpicker56
It seems to be the average dreadnought size, but take the guitar and case to your local music store and ask a technician to measure them for you.

Mikey, just Mikey
Don't bring your guitar. You can never be certain that they will allow you to carry it onto the passenger cabin, no matter what someone on the phone promised you a week or a day before your flight. If the gate attendant thinks the cabin's storage is too full you'll be forced to surrender it and your precious guitar will be handed over to the baggage monkeys who take a great sadistic delight in smashing your guitar. Your best bet is to buy a good flight case like a Calton but that costs more than your guitar and airline ticket put together depending on where you're going. Check out this video (it's fun):