Free · Clinical measurement relationships

ECG Grid Time Converter

Convert small or large ECG boxes to elapsed seconds at 25 or 50 millimeters per second.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Health results are educational estimates, not a diagnosis or treatment recommendation. A qualified clinician can interpret measurements in the context of your health.

Formula and method

Five small boxes at 25 mm/s represent 0.2 seconds.

Seconds = boxes × box width in mm / paper speed in mm/s.

Worked example

Enter these known values and leave the other values blank.

Number of boxes
5
Duration
0.2 sec

Assumptions and limitations

  • Measure horizontal paper distance. A small box is 1 mm and a large box is 5 mm; fractional boxes are allowed. Confirm the recording speed before interpreting an interval. This tool calculates time only, not heart rhythm.
  • Local arithmetic preserves captured unit controls and supported inverses. Clear the unknown field and enter sufficient independent measurements; a zero denominator cannot identify a unique inverse.

Common questions

How is this result calculated?

Seconds = boxes × box width in mm / paper speed in mm/s.

What limits apply to this model?

Measure horizontal paper distance. A small box is 1 mm and a large box is 5 mm; fractional boxes are allowed. Confirm the recording speed before interpreting an interval. This tool calculates time only, not heart rhythm.

References

Bookify adds independently reviewed bounds: Measured box distance must be positive. Measured elapsed time must be positive.

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