EKG QTc Calculator

QTc = QT / √(RR / 1000)

* Enter QT and RR lengths in small squares or milliseconds (ms). Calculated using the Bazett formula.

EKG QTc Calculation

This calculator provides the following information:

  • QTc Length: Calculated using the Bazett formula (QTc = QT / √RR). You can calculate the normalized QTc value by entering QT and RR lengths in small squares or milliseconds (ms).
  • Small Squares Unit: Each small square is typically considered 0.04 seconds (40ms) at 25mm/s speed. For example, 10 small squares = 400ms.
  • ms Unit: You can directly enter QT and RR lengths in milliseconds (ms).
  • Note: QTc calculation is important in assessing heart rhythm. The normal QTc value is typically between 350-440ms (slight variations may exist between men and women).

Note: This calculator is designed for educational and informational purposes only. Consult your doctor in person for specific conditions.

QRs axis calculator

Other Formulas for QTc

There are other formulas for calculating QTc, for example:

  • Fridericia Formula: QTc = QT / (RR/1000)^(1/3).
    This formula may provide more accurate results when the heart rate is very fast or slow.
  • Hodges Formula: QTc = QT + 1.75 × (heart rate - 60).
    This adjusts based on heart rate.
  • Framingham Formula: QTc = QT + 0.154 × (1 - RR/1000).
    This formula may offer higher accuracy compared to the Bazett formula.

  • Each formula has its own advantages and limitations, so the choice should be made based on the situation.


Normal QTc Range

The normal QTc value is typically as follows:

  • Men: 350-450 ms
  • Women: 360-460 ms

The normal QTc range may vary slightly depending on age, gender, and other physiological factors.



Conditions That May Prolong QTc Length

Cause Details
Medications Certain medications, such as antiarrhythmics, psychiatric drugs, and antibiotics, may prolong QTc duration.
Electrolyte Imbalances Deficiencies in calcium, potassium, or magnesium can prolong QTc duration.
Heart Diseases Conditions such as myocardial ischemia, heart failure, or cardiomyopathies can affect QTc duration.
Congenital Conditions Congenital long QT syndrome (LQT1, LQT2, etc.) can prolong QTc duration.
Other Factors Low body temperature, thyroid dysfunction, or changes in heart rhythm can affect QTc duration.

EKG QTc Calculator Version 1.0

Published: April 27, 2025
Last Updated: April 27, 2025

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