Every company has answered this question differently.  Some use hidden decimal points, while other use invented scales.  To us, there was never any question: measure like the doctors do.  We measure the firmness of our mattresses in mm/Hg (millimeters mercury), the same pressure scale that doctors use when taking blood pressure.  We manufacture in a medical-grade FDA approved facility, so the connection was natural, measure firmness like the doctors.​While our mattresses do allow you to adjust from 0-50, it is important to note that the human body typically maintains an internal pressure of about 32 mm/Hg, so sleeping at a firmness that exceeds 32 could lead to decreased circulation which would in turn create pressure points and lower overall quality of sleep.  note: our mattresses do not contain mercury, to learn more about mm/Hg, click here.