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There isn't exactly an overall xp in this game. This question is pretty vague so I'll provide answers for what I think you could be asking.

If you are refering to your total might, you can see it on top of your in-game screen. It will be a number beside your avatar. This is how a players overall strength is displayed. This number combines might gained from research, building, and troops currently in your army. Keep in mind that your might will go down if you lose troops.

If you are refering to the total xp of your dragon, I do not believe there is a way to see that. However, there may be calculators or an excel spread sheet which will show the total experience required to reach a certain level. You can see your dragons current xp if you click on the arrow on the bottom left of your in-game screen, click on dragons, and click on the specific dragon you want to look at. Above the dragon you will see the xp your dragon currently has and how much is needed til his next level.