The FEV3-to-FVC Ratio is the volume of air expired in the first 3 seconds, expressed as a percentage of FVC.
FEV3-to-FVC ratio =
= (FEV in first 3 seconds of expiration) / (FVC) * 100%
FEV3 to FVC ratio in percent for White males 15 - 91 years of age (Crapo, 1981) =
= ((-0.0627) * (height in cm)) - (0.145 * (age in years)) + 112.09
FEV3 to FVC ratio in percent for White females 15 - 91 years of age (Crapo, 1981) =
= ((-0.0937) * (height in cm)) - (0.163 * (age in years)) + 118.16
