Chads2 Score Calculator
Calculate the CHADS2 stroke risk score for patients with non-valvular atrial fibrillation. Enter values for instant results with step-by-step formulas.
Formula
CHADS2 = C + H + A + D + S2
Each risk factor scores 1 point (CHF, Hypertension, Age ≥75, Diabetes) except prior Stroke/TIA which scores 2 points. Total ranges from 0-6. Higher scores indicate greater annual stroke risk.
Worked Examples
Example 1: Elderly Patient with Hypertension and Diabetes
Problem: A 78-year-old patient with atrial fibrillation has hypertension and type 2 diabetes. No history of stroke or heart failure. Calculate the CHADS2 score.
Solution: C (CHF) = 0\nH (Hypertension) = 1\nA (Age ≥75) = 1\nD (Diabetes) = 1\nS2 (Stroke/TIA) = 0\nTotal CHADS2 = 0 + 1 + 1 + 1 + 0 = 3\nAnnual stroke risk: ~5.9%
Result: CHADS2 = 3 | Risk: Moderate-High | Annual stroke rate: 5.9% | Oral anticoagulant recommended
Example 2: Young Patient with Prior Stroke
Problem: A 62-year-old patient with AF has a history of prior TIA but no other risk factors. Calculate the CHADS2 score.
Solution: C (CHF) = 0\nH (Hypertension) = 0\nA (Age ≥75) = 0\nD (Diabetes) = 0\nS2 (Stroke/TIA) = 2\nTotal CHADS2 = 0 + 0 + 0 + 0 + 2 = 2\nAnnual stroke risk: ~4.0%
Result: CHADS2 = 2 | Risk: Moderate | Annual stroke rate: 4.0% | Anticoagulation recommended
Frequently Asked Questions
What is the CHADS2 score?
The CHADS2 score is a clinical prediction tool used to estimate the risk of stroke in patients with non-valvular atrial fibrillation (AF). It was developed by Brian Gage and colleagues and published in 2001. The acronym stands for Congestive heart failure, Hypertension, Age 75 or older, Diabetes mellitus, and prior Stroke or TIA (which receives 2 points, hence the subscript 2). The score ranges from 0 to 6, with higher scores indicating greater annual stroke risk. It helps clinicians decide whether to prescribe anticoagulation therapy. The CHADS2 score has been widely validated in multiple populations and remains a simple, practical tool for initial stroke risk stratification in atrial fibrillation patients.
How is the CHADS2 score calculated?
The CHADS2 score is calculated by assigning points for each risk factor present: Congestive heart failure (1 point) for a history of heart failure or reduced left ventricular ejection fraction; Hypertension (1 point) for blood pressure consistently above 140/90 mmHg or currently on antihypertensive medication; Age 75 years or older (1 point); Diabetes mellitus (1 point) for fasting glucose above 125 mg/dL or on hypoglycemic treatment; and Stroke or TIA history (2 points) for any prior cerebrovascular event. The total score ranges from 0 to 6. Each point increase corresponds to a significant increase in annual stroke risk, from approximately 1.9% at score 0 to 18.2% at score 6.
What is the difference between CHADS2 and CHA2DS2-VASc?
The CHA2DS2-VASc score is an updated and more refined version of the CHADS2 score. While CHADS2 has 5 risk factors totaling a maximum of 6 points, CHA2DS2-VASc adds three additional factors: Vascular disease (prior MI, peripheral artery disease, or aortic plaque), Age 65-74 (1 point), and Sex category (female sex, 1 point), while Age 75 or older receives 2 points instead of 1. CHA2DS2-VASc ranges from 0 to 9 and is better at identifying truly low-risk patients who can safely avoid anticoagulation. Current guidelines from the European Society of Cardiology preferentially recommend CHA2DS2-VASc, though CHADS2 remains widely used due to its simplicity and extensive validation.
When should anticoagulation be started based on CHADS2 score?
Anticoagulation recommendations based on CHADS2 score generally follow these guidelines: Score 0 indicates low risk (approximately 1.9% annual stroke rate), and aspirin alone (75-325 mg daily) or no therapy may be appropriate. Score 1 represents moderate risk (2.8% annual rate), where either aspirin or oral anticoagulation can be considered based on patient preference and bleeding risk. Score 2 or higher indicates that oral anticoagulation is recommended unless contraindicated, as the annual stroke risk exceeds 4%. Options include warfarin (target INR 2.0-3.0) or direct oral anticoagulants (DOACs) such as apixaban, rivarelbaan, dabigatran, or edoxaban. The bleeding risk (assessed with HAS-BLED score) should always be weighed against the stroke prevention benefit.
What are the limitations of the CHADS2 score?
The CHADS2 score has several recognized limitations. First, it classifies a large proportion of patients as intermediate risk (score 1), making treatment decisions uncertain for this group. Second, it does not account for several important stroke risk factors including vascular disease, age 65-74, and female sex, which are captured by the CHA2DS2-VASc score. Third, all included risk factors are weighted equally (except stroke), despite evidence that some factors carry higher risk than others. Fourth, it was validated primarily in North American and European populations and may not perform equally across all ethnic groups. Fifth, it does not incorporate bleeding risk assessment, so clinicians must separately evaluate contraindications to anticoagulation. Despite these limitations, its simplicity makes it useful for rapid bedside risk stratification.
How do I interpret the result?
Results are displayed with a label and unit to help you understand the output. Many calculators include a short explanation or classification below the result (for example, a BMI category or risk level). Refer to the worked examples section on this page for real-world context.