CHADS2 Stroke Risk Score Calculator

Both scores add up points for the same core risk factors: congestive heart failure, hypertension, diabetes, and prior stroke or TIA (worth 2 points in both systems). CHA2DS2-VASc adds three more: vascular disease (prior heart attack, peripheral artery disease, or aortic plaque), an intermediate age-65-to-74 tier worth 1 point, and female sex, worth 1 point. It also splits CHADS2's single "age 75 or older" criterion into two tiers, since CHA2DS2-VASc gives age 75+ a full 2 points instead of 1.

In practice, CHA2DS2-VASc classifies far more patients into a genuine "high risk" category, specifically because it's better at pulling low-risk-looking patients with a CHADS2 score of 0 or 1 out of that bucket once their vascular disease, age, or sex is accounted for:

These percentages describe how one real patient population gets sorted into each risk category by each scoring system, not the individual stroke-risk percentages themselves (see the next section for those).

A Note on Female Sex and the CHA2DS2-VASc Score

A CHA2DS2-VASc point for female sex only matters clinically when it's the ONLY point a patient has. A woman under 65 with no other risk factors and a score of 1 (from sex alone) is still treated as low risk, the same as a man with a score of 0, and anticoagulation is generally not recommended. This is a genuinely easy detail to miss, and this calculator's anticoagulation guidance accounts for it directly.

Each score corresponds to a real, published annual stroke risk percentage, not an arbitrary label. This calculator's CHA2DS2-VASc percentages come from the Swedish Atrial Fibrillation cohort study (Friberg et al., 2012), one of the largest real-world validations of the score:

The original CHADS2 percentages come from its own 2001 validation study (Gage et al.):

Different validation studies produce somewhat different precise percentages for the same score, since each was measured in a different real patient population. Use these as a genuine reference point, not an exact individual prediction.

For CHA2DS2-VASc, current guidance uses sex-adjusted thresholds:

• Score of 0 (male) or 1 (female, from sex alone): low risk, anticoagulation generally not recommended
• Score of 1 (male) or 2 (female): moderate risk, anticoagulation may be considered based on individual factors
• Score of 2 or higher (male) or 3 or higher (female): anticoagulation is generally recommended

Before starting anticoagulation, guidelines also call for assessing bleeding risk with a dedicated tool such as HAS-BLED, alongside a direct conversation with the patient about risks, benefits, and preferences. This calculator doesn't estimate bleeding risk, only stroke risk.

For patients with a high-risk score who have a genuine contraindication to oral anticoagulation, left atrial appendage (LAA) occlusion, a procedure to close off the part of the heart where AFib-related clots most often form, may be considered as an alternative, per current guidelines.

Neither score should be applied to valvular atrial fibrillation, where stroke risk is driven by the valve disease itself rather than these risk factors. Both scores are also modest predictors on their own: in head-to-head comparisons, CHADS2 and CHA2DS2-VASc have C-statistics of roughly 0.64 and 0.65 respectively, well below the 0.7+ threshold generally considered a strong individual predictor. Their real value is standardizing a conversation about risk, not replacing clinical judgment.

A newer variant, CHA2DS2-VA, removes the sex-category point entirely and has been proposed in some 2024 European guidelines. It hasn't seen meaningful real-world adoption or search demand yet, so it isn't included as a separate mode here, but the female-sex nuance above reflects the same underlying debate about whether sex alone should change a treatment decision.

Stroke and bleeding risk scores are typically reviewed alongside a few other bedside clinical calculations:

• Wells Score Calculator (DVT Risk): another clinical risk-scoring tool using the same points-based format, for deep vein thrombosis risk instead of stroke risk.
• Mean Arterial Pressure (MAP) Calculator: a quick bedside cardiovascular calculation often reviewed in the same clinical context.