Calculate CHADS2 Score
Use this quick calculator for educational estimation of stroke risk in patients with non-valvular atrial fibrillation.
The CHADS2 score is one of the classic clinical tools used to estimate annual stroke risk in people with atrial fibrillation (AF). If you are learning about anticoagulation decisions or trying to understand your care plan, this calculator gives you a straightforward way to see how the score is built.
What is the CHADS2 score?
CHADS2 is a point-based risk model developed to estimate stroke risk in non-valvular AF. Each letter in the acronym represents a major risk factor. Most factors contribute 1 point, while prior stroke or TIA contributes 2 points because of its stronger association with recurrent events.
- C — Congestive heart failure: 1 point
- H — Hypertension: 1 point
- A — Age 75 years or older: 1 point
- D — Diabetes mellitus: 1 point
- S2 — Prior stroke/TIA: 2 points
Total score ranges from 0 to 6. Higher scores indicate greater annual stroke risk.
CHADS2 criteria and points
| Risk Factor | Points | Clinical Note |
|---|---|---|
| Congestive heart failure | 1 | Past or current heart failure symptoms/signs |
| Hypertension | 1 | History of high blood pressure, treated or untreated |
| Age ≥ 75 | 1 | Applies based on age at assessment |
| Diabetes mellitus | 1 | Type 1 or type 2 diabetes |
| Prior stroke or TIA | 2 | Weighted more heavily due to recurrence risk |
How to use this calculator correctly
Step 1: Enter age
Input the patient’s age in years. The calculator automatically adds +1 if age is 75 or older.
Step 2: Check all relevant conditions
Select each condition that applies today or by past medical history. If uncertain, verify with a clinician or chart documentation.
Step 3: Review score, risk estimate, and category
The calculator returns a total score, estimated annual stroke risk (from original CHADS2 cohorts), and a broad risk category to support discussion.
Interpreting the result
Here is the commonly cited annual stroke risk mapping for CHADS2:
| CHADS2 Score | Estimated Annual Stroke Risk |
|---|---|
| 0 | ~1.9% |
| 1 | ~2.8% |
| 2 | ~4.0% |
| 3 | ~5.9% |
| 4 | ~8.5% |
| 5 | ~12.5% |
| 6 | ~18.2% |
These values are estimates and can differ by cohort, treatment era, and individual patient profile. Modern care decisions should include bleeding risk, patient preferences, renal function, drug interactions, and guideline updates.
CHADS2 vs. CHA2DS2-VASc
Many current guidelines prefer the CHA2DS2-VASc score because it refines risk classification, especially for lower-risk patients. It adds vascular disease, age 65–74, and sex category to improve sensitivity. Even so, CHADS2 remains a useful teaching framework and appears in legacy studies and tools.
Practical limitations to remember
- CHADS2 does not include all risk modifiers used in modern practice.
- It does not assess bleeding risk (often estimated separately with tools such as HAS-BLED).
- Clinical context matters: valve disease, kidney disease, frailty, and medication adherence can all influence decisions.
- Scores support decisions; they do not replace shared clinician-patient planning.
Frequently asked questions
Is a higher score always an automatic anticoagulation decision?
Not automatically. A higher score usually increases concern for stroke risk, but treatment still depends on bleeding risk, contraindications, and patient values.
Can this score change over time?
Yes. As patients age or develop additional conditions like hypertension or diabetes, the score can increase and management may need re-evaluation.
Does this calculator store my information?
No. This single-page tool runs in your browser and does not send your values to a server.
Bottom line
The CHADS2 score is simple, fast, and still helpful for understanding stroke risk in atrial fibrillation. Use it as an educational starting point, then confirm final management with a licensed healthcare professional using up-to-date clinical guidelines.