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Pulmonary Function - Reference Normal Predicted Values Calculator

Predicted Normal Values

Many studies have published lung function reference values for a variety of race/ ethnic groups, countries, and age ranges. Populations of interest are sampled and spriometric studies were done and statistical analyis was used to determine "normal" results for each parameter of interest.

It was found that general equations could be made to describe the variation of each predicted value by e.g., age, sex, etc. Historically these results were made available in graphical form, and clinicians would "look up" the desired normal value. Today, most modern spirometers may have some predicted value calculators built-in.
These predicted values, together with relevant patient information can provide useful clinical information. For example, for any patient it became possible to determine the expected respiratory parameters (FVC, PEF, etc.), as well as a standard deviation based on the patients' age, sex and sometimes other information.

How this calculator works

This calculator will compute the normal values for 16 different references.
Some references should be pointed out as they were highlighted as "recommended" by the European Respiratory Society (ERS Quanjer 1993), and the American Thoracic Society (NHANESIII, by Hankinson et al.). For information on the equations used in this calculator, as well as details on the sample populations please consult the desired references directly.

View list of references available

To use the calculator please enter the patient's basic information, and then select the method to display the results. This can be either:

By desired reference:  a complete listing of all parameters by a specific reference 


By desired parameter:  select any desired parameter (e.g., Peak Expiratory Flow), and calculate the predicted values from all 16 refences for comparison.

For further reading on predicted values and their use the following books are also highly recommended:

Recommended books on spirometry


Required by most predicted values references:

Date of birth



Ethnic group

Required by some predicted values references:

   -  (Dockery 1983, Hedenström 1986, Roca 1982)
Tobacco use (g/day)
Smoke years
Pack years
   -  (Hedenström 1986)

Select method to display results:

By desired reference
By desired parameter


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