[2D] Getting the y coordinate of the top of a game object

I'm working on some ladder-climbing functionality, and I need to get the y coordinates of the top of the player and the ladder they're trying to climb. I thought I could get the y coordinate of the top of a sprite game object like so:

transform.position.y + (spriteRenderer.bounds.size.y / 2)

But apparently, that's not quite right. Despite the player clearly being above the ladder, the ladder's top edge value (as calculated by the above algorithm) is higher than that of the player's.

So, how do I go about it? I'm using Unity 5.6.2f1