Why use Fridericia instead of Bazett?

Bazett's formula (QT / RR^0.5) over-corrects at high heart rates and under-corrects at low ones. Fridericia's cube-root exponent (1/3) gives a more linear relationship and is widely used in drug trials and pharmacovigilance.

What is a normal QTcF value?

Standard thresholds: ≤450 ms in men, ≤460 ms in women. Values >500 ms are associated with a significantly elevated risk of torsades de pointes and should prompt immediate clinical evaluation.

Can I enter the RR interval directly instead of heart rate?

Yes — use the RR (ms) input mode. Switch the toggle to "RR interval" and enter the RR in milliseconds. The tool will convert it to seconds before applying the formula.

Does this tool replace clinical judgment?

No. This calculator is an educational and reference tool only. QTc interpretation must account for clinical context, electrolytes, concomitant medications, and patient history. Always consult a qualified clinician.

How is the RR interval derived from heart rate?

RR (seconds) = 60 / heart rate (bpm). For example, a heart rate of 75 bpm gives an RR of 0.800 s, and a heart rate of 100 bpm gives 0.600 s.

What units should I use for the QT interval?

Enter the QT interval in milliseconds (ms), which is the standard unit on most ECG reports. A typical normal QT range is 350–440 ms depending on heart rate and sex.

Corrected QT Fridericia Calculator

Name: Corrected QT Fridericia Calculator
Availability: InStock
Author: Nham Vu

Enter your measured QT interval and heart rate to compute the Fridericia-corrected QTc (QTcF) instantly.

ECG Inputs

QT Interval (ms)

Measured from Q-wave onset to end of T-wave. Typical range: 350–500 ms.

Heart Rate Input

Heart rate (bpm) RR interval (ms)

Heart Rate (bpm)

Biological Sex (for threshold reference)

Male Female

Result

Enter values and press Calculate.

Summary

Enter your measured QT interval and heart rate to compute the Fridericia-corrected QTc (QTcF) instantly.

How it works

Measure the QT interval (ms) from the ECG — start of the Q wave to the end of the T wave.
Note the patient's heart rate (bpm) from the same ECG strip.
The RR interval is derived automatically: RR (s) = 60 / heart rate.
The Fridericia formula is applied: QTcF = QT (ms) / RR(s)^(1/3).
The result is compared against standard normal thresholds for men and women.

Use cases

Assess QT prolongation risk before prescribing QT-prolonging drugs.
Monitor patients on antiarrhythmics, antipsychotics, or antibiotics.
Screen ECG data in clinical trials where Fridericia is the preferred correction.
Compare QTc values across patients with different resting heart rates.
Evaluate drug-induced QT changes at heart rates where Bazett over-corrects.
Teaching cardiology and pharmacology students the difference between correction methods.

Frequently Asked Questions

Last updated: 2026-07-22 · Reviewed by Nham Vu