Normal Peak Flow Rate Calculator
Male
Female
Your Estimated Normal Peak Flow:
—
L/min
Asthma Action Plan Zones:
Green (80-100%): Above — L/min
Yellow (50-80%): — to — L/min
Red (Below 50%): Below — L/min
What is Peak Expiratory Flow Rate (PEFR)?
Peak Expiratory Flow Rate (PEFR) is a measurement of how fast a person can exhale air from their lungs. This measurement is crucial for individuals with asthma or chronic obstructive pulmonary disease (COPD) to monitor their lung function and the effectiveness of their treatment.
How to Use the Peak Flow Calculator
This calculator uses standardized formulas based on age, height, and sex to estimate your "predicted" normal peak flow. For most adults, height is the most significant factor, followed by age. For children, height is the primary predictor.
Understanding Your Results (The Zone System)
Doctors typically use a "Traffic Light" system to help patients manage asthma based on their personal best or predicted peak flow:
- Green Zone (80-100% of predicted): Your breathing is stable. Continue normal activities and medications.
- Yellow Zone (50-80% of predicted): Caution. You may be having an asthma flare-up. Follow your action plan for medication adjustments.
- Red Zone (Below 50% of predicted): Medical Emergency. Seek immediate medical attention.
Typical Predicted Values Example
| Sex | Age | Height | Predicted PEFR |
|---|---|---|---|
| Male | 25 | 175 cm | ~585 L/min |
| Female | 25 | 165 cm | ~440 L/min |
| Male | 50 | 180 cm | ~555 L/min |
Important Note
While predicted values are a good guide, many physicians prefer to use your "Personal Best" (the highest reading you can achieve when feeling well) as the baseline for your individual asthma action plan. Always consult with a healthcare professional for clinical diagnosis.