Ten validated bedside calculators used daily in cardiology practice, in one place. They run entirely in your browser — nothing is transmitted, stored or logged. They are educational decision support and do not replace clinical judgement: verify every value before it is applied to a patient.
Heart rate
From the RR interval in milliseconds, or from large boxes counted on a 25 mm/s ECG.
Corrected QT interval
Bazett and Fridericia. Fridericia is preferred at heart rates outside 60–100.
Ejection fraction and fractional shortening
Simpson volumes, or linear left ventricular dimensions.
Stroke volume and cardiac output
LVOT method: SV = 0.785 × D² × VTI.
Aortic valve area
Continuity equation. Severe stenosis is an area below 1.0 cm².
Weight-based infusion
Convert between dose in mcg/kg/min and pump rate in mL/hour.
Creatinine clearance
Cockcroft–Gault, for renal dose adjustment.
Mean arterial pressure and body surface area
MAP from cuff pressure; BSA by Mosteller and Du Bois.
CHA₂DS₂-VASc
Annual stroke risk in non-valvular atrial fibrillation.
HAS-BLED
Major bleeding risk on oral anticoagulation. A high score prompts correction of modifiable factors, not withholding anticoagulation.
Notes on the formulas used
- QTc. Bazett over-corrects at fast rates and under-corrects at slow ones; Fridericia is the more reliable of the two outside 60–100 bpm and is what the output judges against. Upper limits taken as 450 ms in men and 460 ms in women.
- Ejection fraction. Simpson’s biplane method of discs is the reference standard; linear dimensions give fractional shortening, which is unreliable where wall motion is regional.
- Continuity equation. Aortic valve area is most sensitive to the LVOT diameter, which is squared — a 1 mm measurement error changes the calculated area by roughly 10 per cent. Cross-check against the dimensionless index, which does not depend on the diameter at all.
- Cockcroft–Gault. Still the equation on which most cardiac and anticoagulant dose adjustments were validated, which is why it is used here in preference to CKD-EPI for dosing decisions.
- CHAâ‚‚DSâ‚‚-VASc. Annual stroke rates are the commonly cited cohort figures and vary between populations. A score of 1 derived from female sex alone does not by itself warrant anticoagulation.
- HAS-BLED. A high score identifies modifiable risk and a need for closer review. It is not a reason to withhold anticoagulation from a patient who needs it.
Where the reasoning behind these is set out
The calculators give a number; the decision needs the reasoning. Valve assessment and echocardiographic measurement are covered in the diagnosis and imaging reading list, antithrombotic strategy and bleeding risk in the interventional and acute care list, and rhythm and risk scoring in the heart failure, rhythm and risk list. Free teaching articles are in the learning centre, and structured teaching in the course programme.
These tools are educational decision support. They support clinical judgement and do not replace it. Verify every value independently before it informs the care of a patient.