Stand against a flat wall on a hard, level floor
Remove shoes, hats, and bulky hair accessories
Keep heels, buttocks, shoulders, and head touching the wall
Look straight ahead with your chin level
Place a flat object like a book on your head, making it level with the floor
Mark the wall where the bottom of the object touches
Measure from the floor to the mark using a tape measure or ruler
Do the measurement in the morning for the most consistent result
Repeat the measurement 2 to 3 times and use the average
If possible, have someone else help for better accuracy