ECG Boxes to Seconds Calculator
Convert ECG grid measurements to time duration in seconds and milliseconds
ECG Timing Measurement
Count the ECG boxes between two points of interest
Time Duration Results
Calculation Breakdown
Box size: 1 mm per box
Total distance: 5 x 1 = 5 mm
Paper speed: 25 mm/s
Duration = 5 mm ÷ 25 mm/s = 0.200 seconds
Clinical Interpretation
PR interval: Normal PR interval duration
How to Measure ECG Boxes
Step-by-Step Method
- 1. Place one tip of your caliper at the first point (e.g., beginning of P wave)
- 2. Place the other tip at the second point without moving the first tip
- 3. Without changing the angle, move the caliper to align with ECG grid lines
- 4. Count the number of boxes between the measuring tips
- 5. Use this calculator to convert boxes to time duration
Example: PR Interval Measurement
Measured: 4 small boxes between P wave start and QRS start
Calculation: 4 boxes × 1mm × (1s ÷ 25mm) = 0.160 seconds = 160ms
Interpretation: Normal PR interval (120-200ms range)
Normal ECG Values
*QT interval should be corrected for heart rate
ECG Grid Reference
At 25 mm/s (Standard)
At 50 mm/s (High Speed)
Clinical Significance
Prolonged PR (>200ms)
May indicate first-degree heart block
Short PR (<120ms)
Possible Wolf-Parkinson-White syndrome
Wide QRS (>120ms)
Ventricular conduction abnormality
Medical Disclaimer
This calculator is for educational purposes only and should not replace professional medical advice. ECG interpretation requires specialized training and clinical context. Accurate ECG measurements should be performed by qualified healthcare professionals using proper equipment and techniques. Always consult with a cardiologist or physician for proper ECG interpretation and clinical decision-making.
Understanding ECG Timing and Measurements
What is ECG Grid Paper?
ECG paper consists of a standardized grid system where horizontal lines represent time intervals and vertical lines represent voltage. The timing measurements are crucial for identifying normal and abnormal cardiac rhythms and conduction patterns.
Why Accurate Timing Matters
- •Diagnose heart blocks and conduction delays
- •Identify arrhythmias and rhythm disorders
- •Assess cardiac electrical activity timing
- •Monitor drug effects on cardiac conduction
Common ECG Intervals
PR Interval
Time from P wave start to QRS start. Represents atrial depolarization and AV conduction delay.
QRS Complex
Duration of ventricular depolarization. Widening suggests conduction abnormalities.
QT Interval
Total ventricular electrical activity time. Must be corrected for heart rate (QTc).
ECG Paper Speed Settings
25 mm/s (Standard Speed)
- • Most commonly used in clinical practice
- • Each small box = 0.04 seconds (40 milliseconds)
- • Each large box = 0.2 seconds (200 milliseconds)
- • Better for rhythm analysis and heart rate calculation
- • Standard for most diagnostic interpretations
50 mm/s (High Speed)
- • Used for detailed interval measurements
- • Each small box = 0.02 seconds (20 milliseconds)
- • Each large box = 0.1 seconds (100 milliseconds)
- • Better resolution for precise timing analysis
- • Useful for QT interval measurement and pacemaker analysis