ECG Reference: Intervals, Criteria and Calculators

Free ECG reference for clinicians: normal values, criteria and patterns with what to do next, the studies behind them, and calculators for the QTc, the axis, Sgarbossa and AV block.

ECG calculators

Free calculatorQTc calculatorBazett, Fridericia, Framingham and Hodges side by side, with the heart-rate caveat.
Free calculatorSgarbossa checkerOriginal and Smith-modified criteria for MI in left bundle branch block or a paced rhythm.
Free calculatorAxis calculatorThe frontal axis in degrees from two or more limb leads, with the band it falls in.
Free calculatorAV block helperAnswer three questions about the P waves and the PR to name the block and where it likely sits.

Intervals and axis

Conduction blocks

Ischemia and its mimics

Electrolytes and channelopathies

Pre-excitation and arrhythmias

Wolff-Parkinson-White Pattern on ECGA short PR under 120 ms, a delta wave, a QRS over about 110 ms, and ST segments and T waves pointing away from the delta wave.

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For health care professionals. Values are for adults unless a page says otherwise.

ECG Reference: Intervals, Criteria and Calculators

ECG calculators

Intervals and axis

Conduction blocks

Ischemia and its mimics

Electrolytes and channelopathies

Pre-excitation and arrhythmias

Go deeper into the evidence.

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