How is the corrected QT calculated?

From the QT you measure and the heart rate (RR in seconds = 60 ÷ heart rate): Bazett = QT ÷ √RR; Fridericia = QT ÷ ∛RR; Framingham = QT + 154 × (1 − RR); Hodges = QT + 1.75 × (heart rate − 60). The tool shows all four in milliseconds.

Which QTc formula should I use?

Bazett is the historical default and is accurate at 60–100 bpm, but it over-corrects at high rates and under-corrects at low rates. Outside 60–100 bpm, Fridericia or Framingham track the true value better — so the tool shows all four side by side.

What QTc counts as prolonged?

Per the cited source, a QTc above 440 ms in men and above 460 ms in women is prolonged, and above 500 ms is markedly prolonged with increased torsades risk. These are thresholds, not a diagnosis.

Does the tool diagnose long QT syndrome?

No. It corrects a QT you measured and flags published thresholds. It does not measure the QT for you, diagnose long QT syndrome, or recommend any drug change — interpret against your cardiology guideline.

Does any of the data I enter leave my browser?

No. The calculation runs entirely in your browser; nothing you enter is sent to a server or stored. The print option produces a clean worksheet you can save as a PDF.

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Corrected QT (QTc) calculator

Enter the QT interval you measured off the ECG and the heart rate for the Bazett, Fridericia, Framingham, and Hodges corrected QT side by side, with the published >440 ms (men) / >460 ms (women) prolongation thresholds. A measurement aid, not a diagnosis — and nothing you enter leaves your device.

Measured QT (ms)

You supply the QT interval you measured off the ECG. This tool does not measure QT for you.

Heart rate (bpm)

RR (seconds) = 60 ÷ heart rate. Enter whichever you have.

Rate input

Sex (Bazett threshold)

Corrected QT (QTc)

Male threshold > 440 ms

BazettHistorical default; accurate at 60–100 bpm447ms

FridericiaCube-root correction; better outside 60–100 bpm431ms

FraminghamLinear correction; better outside 60–100 bpm431ms

HodgesRate-based linear correction426ms

Bazett: Prolonged for this sex

Measurement aid, not a diagnosis. This reproduces published rate-correction formulae (Bazett, Fridericia, Framingham, Hodges) and published QTc thresholds; you supply the QT interval you measured off the ECG. It does not measure QT for you, does not diagnose long QT syndrome, and does not recommend starting, stopping, or dosing any drug. Bazett is accurate at heart rates of 60–100 bpm but over-corrects at high rates and under-corrects at low rates, so read Fridericia or Framingham outside that range. Verify the QT measurement and interpret against your current cardiology/national guideline. Reviewed June 2026.

Privacy: Runs entirely in your browser — nothing you enter is sent to a server or stored.

Formulae and thresholds reproduced from: Long QT Syndrome (sex-specific QTc thresholds >440 ms men / >460 ms women, >500 ms markedly prolonged). StatPearls / NCBI Bookshelf NBK441860.; QT correction formulae (Bazett/Fridericia/Framingham/Hodges) — Fasa PERSIAN cohort, Table 1 (PMC8851728)..

How the corrected QT works

The QT interval shortens as the heart rate rises, so it is ‘corrected’ to a rate-independent QTc for comparison. Four formulae are in common use — Bazett, Fridericia, Framingham, and Hodges — and they diverge at the extremes: Bazett is reliable at 60–100 bpm but over-corrects when the heart is fast and under-corrects when it is slow. This tool shows all four side by side from the QT you measure, and flags the published prolongation thresholds; it never measures the QT for you or makes a diagnosis.

Many teams re-correct the QT by hand on every ECG. If you run a cardiology clinic workflow on Avinya Plus, the QT and heart rate can live on the note and the formula engine can compute the QTc automatically — so the corrected value sits beside the tracing instead of on a calculator. The arithmetic is the engine's; the judgement stays yours.

Frequently asked questions

How is the corrected QT calculated?: From the QT you measure and the heart rate (RR in seconds = 60 ÷ heart rate): Bazett = QT ÷ √RR; Fridericia = QT ÷ ∛RR; Framingham = QT + 154 × (1 − RR); Hodges = QT + 1.75 × (heart rate − 60). The tool shows all four in milliseconds.
Which QTc formula should I use?: Bazett is the historical default and is accurate at 60–100 bpm, but it over-corrects at high rates and under-corrects at low rates. Outside 60–100 bpm, Fridericia or Framingham track the true value better — so the tool shows all four side by side.
What QTc counts as prolonged?: Per the cited source, a QTc above 440 ms in men and above 460 ms in women is prolonged, and above 500 ms is markedly prolonged with increased torsades risk. These are thresholds, not a diagnosis.
Does the tool diagnose long QT syndrome?: No. It corrects a QT you measured and flags published thresholds. It does not measure the QT for you, diagnose long QT syndrome, or recommend any drug change — interpret against your cardiology guideline.
Does any of the data I enter leave my browser?: No. The calculation runs entirely in your browser; nothing you enter is sent to a server or stored. The print option produces a clean worksheet you can save as a PDF.

Sources

The four correction formulae are reproduced from the Fasa PERSIAN cohort (PMC8851728, Table 1) and the canonical MDCalc/textbook coefficients; the >440/>460/>500 ms thresholds from StatPearls Long QT Syndrome (NBK441860). Bazett's rate-dependence caveat is from the same source. Reviewed against the sources on 2026-06-29.

Keep the QTc on the cardiology record.

In Avinya Plus you can build the QT and heart rate into a cardiology template and let the formula engine compute the QTc automatically. See it on a quick demo.