What is the FEV1/FVC?
What is the predicted FEV1/FVC?
Take the FEV1/FVC and divide it by the predicted FEV1/FVC then multiply the answer by 100. This gives you the % predicted FEV1/FVC.
(Example: if the FEV1/FVC is 80.1% and the predicted FEV1/FVC is 82.3% the equation would be 80.1/82.3*100=)