Which of the following is a normal QRS duration value?

• A. <120 ms
• B. >200 ms
• C. 40-60 ms
• D. 150-170 ms

Answer: (A)

QRS duration shows how long ventricular depolarization takes on the ECG. In a healthy heart, this happens quickly, so the QRS complex is narrow. The normal upper limit is about 120 milliseconds (0.12 seconds), with many sources citing 60–100 ms as typical. Therefore, a QRS duration shorter than 120 ms is considered normal. When the QRS duration exceeds 120 ms, it signals delayed intraventricular conduction, such as a bundle branch block or other conduction abnormalities. Values like 150–170 ms or over 200 ms clearly indicate abnormal conduction. A value of 40–60 ms is shorter than typical for adults and is not regarded as the normal range in standard ECG interpretation.