What is the normal duration of the QRS complex?

• A. 0.04-0.08 sec
• B. 0.08-0.12 sec
• C. 0.12-0.16 sec
• D. 0.20-0.24 sec

Answer: (B)

Ventricular depolarization time is what the QRS duration reflects. In a healthy heart, the impulse travels quickly through the His‑Purkinje system, so the ventricles activate in a brief, tightly timed burst, producing a narrow QRS complex.

The normal range is about 0.08 to 0.12 seconds (80–120 milliseconds), which on a standard ECG spans roughly 2–3 small boxes (each small box is 0.04 seconds). This narrow window indicates efficient, rapid conduction through the ventricles.

If the QRS duration exceeds 0.12 seconds, it suggests a conduction delay or block within the ventricles (such as a bundle branch block or ventricular rhythm). Shorter than the normal range isn’t typical for standard ventricular depolarization, so the 0.08–0.12 second window is the reference for normal.