🌬️ Peak Flow Calculator – Estimated Peak Expiratory Flow
Estimate your predicted Peak Expiratory Flow Rate (PEFR) – the fastest speed of air you can exhale – based on your age, height, and sex.
What is Peak Expiratory Flow?
Peak Expiratory Flow Rate (PEFR) measures how fast you can force air out of your lungs after a full breath in. It’s commonly tracked with a home peak flow meter to help monitor conditions like asthma, since a drop from your personal best can be an early sign of narrowing airways.
How this calculator works
This tool uses the Nunn and Gregg regression equations, widely referenced predictive formulas for PEFR in adults based on age, height, and sex, derived from population studies of lung function. The result is your predicted ‘normal’ peak flow; the lower limit of normal shown is commonly estimated as about 80% of the predicted value.
Your own personal best peak flow, measured when you are feeling well, is generally more useful for day-to-day monitoring than a population-predicted value, since individual lung function varies. This calculator is for general educational reference only and does not replace guidance from your doctor on managing a respiratory condition.