What is Peak Expiratory Flow (PEF)?

PEF is the maximum speed of exhalation, measured in liters per minute (L/min). It's a key daily monitoring metric for asthma patients, reflecting large airway patency.

How to interpret peak flow values?

Green zone (>80% of personal best): well controlled. Yellow zone (50-80%): caution, may need medication adjustment. Red zone (<50%): medical emergency — seek immediate care.

How to use a peak flow meter?

1) Stand or sit upright; 2) Set pointer to zero; 3) Take a deep breath; 4) Seal lips around mouthpiece; 5) Blow out as hard and fast as possible; 6) Record reading. Repeat 3 times, use highest value. Measure morning and evening daily.

Peak Flow Calculator | Free ToolBase

Home › Tools › Peak Flow Calculator

Free online Peak Expiratory Flow (PEF) calculator. Predict normal PEF based on age, gender, and height. Get green/yellow/red zone ranges for asthma management.

Zero dependencies · Works offline

📋 Input Parameters

Gender

Age (years)

Height (cm)

📖 About Peak Flow

What is PEF?

Peak Expiratory Flow measures the maximum speed of exhalation (L/min). It's vital for daily asthma monitoring and reflects large airway function.

Finding personal best

Measure 2-3 times daily for 2-3 weeks when well-controlled. Use the highest value as your personal best. This calculator provides a predicted normal based on demographics.

🫁 Peak Flow Calculator

📋 Input Parameters

📖 About Peak Flow

What is PEF?

Finding personal best