The center space on my middle finger is exactly one inch in length
The width of the top section of my middle finger is a half of an inch
The width of the very tip of my pinky finger is a quarter of an inch
Of course these measurements may vary for different people. I have very small dainty-like fingers, lol. I encourage everyone to measure their own fingers before actually attempting to finger a trim measurement. If not, you might take off more than you think!
I used finger trimming in this video: Trimming Natural Hair