ECG Heart Rate Calculator

This calculator turns what you counted on an ECG strip into a heart rate. Count the boxes between two R waves and it applies the 300 rule for large boxes or the 1500 rule for small ones, adjusted if the paper ran at 50 mm per second instead of 25. Count QRS complexes on a six or ten second strip instead and it scales that to a minute, which is the method that survives an irregular rhythm. A third tab takes an RR interval already measured in milliseconds or seconds. Every answer comes with the working, the interval in both paper and time units, and the adult range it falls in.

Calculator Type

The 300 and 1500 rules. Regular rhythms only: one RR interval is being multiplied up to a minute.

Measured R wave to R wave. Fractions are fine: 4.5 large boxes is a real reading.
The millimetres are the ruling of the paper, which is 1 mm and 5 mm on every ECG strip made anywhere, so there is nothing to choose and no unit control on this page. What you enter is a count of boxes, which has no unit at all.
Read it off the corner of the strip; the recorder prints it. These are the only two speeds in use and both are defined in mm/s by the recording standards, so this is a choice of setting rather than of units.
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The method for an irregular rhythm: count QRS complexes over a known length of paper and scale to a minute.

Count the R waves on the strip. A half complex at the end is usually counted as a half.
Seconds, which is what this method counts in; the box equivalents are given for the standard 25 mm/s paper so you can measure the strip if it is not marked. A 12 lead recording is 10 seconds wide.
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Measured In

When the interval is already measured, in milliseconds or seconds.

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