Neither the hopper wiki article, nor the "standard" article on block heights discusses this.

2 Answers

The outer rim of the hopper is a full 1 meter (16 pixels) upwards from the bottom, the inner lowered part is 0.625 meters (10 pixels) high. Note that blocks are 1m^3.

You can use F3 to find the y height of your feet thus the height of blocks you are standing on.

1 block (1 meter) is the height of the hopper and is the basic answer to your question but if you would like to get into depth of the height, the full block is 26 pixels on your computer, and the full shape of the hopper is one square meter.