From a six-second strip, what is the multiplier after counting R waves in 30 small squares?

From a six-second strip, what is the multiplier after counting R waves in 30 small squares?

• A. ×10
• B. ×5
• C. ×2
• D. ×20

Answer: (A)

The rate is estimated from a fixed time window by scaling to a minute. A six-second ECG strip spans 30 large squares (each large square is 0.2 seconds). Counting R waves in those 30 large squares and multiplying by 10 gives the heart rate in beats per minute, because 60 seconds divided by 6 seconds equals 10. So the multiplier is 10. If you were counting in small squares, 30 small squares equals 1.2 seconds, which would require a multiplier of 60/1.2 = 50 to scale to a minute. But with the standard six-second window using large squares, the correct multiplier is 10.

The rate is estimated from a fixed time window by scaling to a minute. A six-second ECG strip spans 30 large squares (each large square is 0.2 seconds). Counting R waves in those 30 large squares and multiplying by 10 gives the heart rate in beats per minute, because 60 seconds divided by 6 seconds equals 10. So the multiplier is 10.

If you were counting in small squares, 30 small squares equals 1.2 seconds, which would require a multiplier of 60/1.2 = 50 to scale to a minute. But with the standard six-second window using large squares, the correct multiplier is 10.