You can check the Defensive and Offensive power of your army – and the power of the Lords and Ladies in your League – from the Statistics section in the "My League" tab of the League Hall.
Please be aware that the values shown on this screen do not always accurately reflect those displayed elsewhere in the game, or indeed the current actual power of a given army.
Discrepancies occur because League Hall statistics are only updated once every 3 hours. Recent Battles/Acquisitions will not be included, and recently expired bonuses may not be factored into your total. Statistics may also change depending on which Crystals are active in the Crystal Vault, and on whether your Paragon Status is active.
It should also be noted that the bonus your army derives from its Legendary Units is calculated directly at the moment when the battle occurs. Your army's strength may vary depending on the supporting Units that are deployed.
In the “Statistics” window, the increase/decrease statistic compares the current overall Offense and Defense power of your Units to their overall Offense/Defense power on the Saturday of the week before.