Why was the battle of bunker hill considered a patriot victory

While the result was a victory for the British, the massive losses they encumbered discouraged them from any further sorties against the siege lines; 226 men were killed with over 800 wounded, including a large number of officers. The battle at the time was considered to be a colonial defeat; however, the losses suffered by the British troops gave encouragement to the colonies, demonstrating that inexperienced militiamen were able to stand up to regular army troops in a pitched battle.

Interestingly enough, the Battle of Bunker Hill was not fought on Bunker Hill, but on the adjacent Breed's Hill.