Risk mitigation
Mask Benefit Estimator
Combine baseline exposure risk with estimated mask filtration efficiencies to gauge how masking reduces transmission. This tool provides illustrative estimates; real-world protection depends on fit, compliance, and other layers like ventilation.
Estimated risk without masks or ventilation (e.g., household exposure ~25%).
“Source control” mask worn by the potentially infectious person.
Protection for the person trying to avoid infection.
Estimated additional reduction from ventilation, distancing, or limited exposure time.
Baseline vs masked
- Baseline risk: 15.0%
- Masked risk: 4.3%
Absolute reduction
10.7%
Relative reduction: 71.2%
Combined source control and wearer protection cut risk by more than half. Keep other mitigations in place.
Combine well-fitting respirators with ventilation and shortened exposure for maximum protection.
How to Use This Calculator
Estimate baseline risk
Use context-specific data (household, indoor dining, classroom). If unknown, assume 10–20% for close unmasked contact.
Choose mask types
Select the mask worn by the infectious source and by the susceptible individual. Upgrade to higher filtration for better protection.
Add ventilation/time limits
Estimate extra risk reduction from open windows, HEPA filtration, or short encounters (e.g., subtract 20–40%).
Formula
Combined mask protection = 1 − (1 − Source efficacy) × (1 − Receiver efficacy)
Total reduction = Combined mask protection + (1 − Combined) × Ventilation reduction
Masked risk = Baseline risk × (1 − Total reduction)
All reductions are expressed as proportions (0–1). Values are illustrative and assume independent layers.
Full Description
Masks lower risk through source control (blocking exhaled particles) and wearer protection (filtering inhaled particles). Effectiveness depends on material, filtration efficiency, fit, and adherence. This calculator demonstrates how layering both parties’ masks plus ventilation dramatically lowers transmission probability.
For highest protection, use fit-tested respirators, ensure good ventilation, keep encounters brief, and stay up to date with vaccinations. Always adapt to current public health guidance and specific pathogen characteristics.
Frequently Asked Questions
Where do the mask percentages come from?
Estimates draw from published filtration studies. Actual performance varies by fit, facial hair, moisture, and mask construction.
Do masks eliminate risk?
No. They substantially reduce risk but other measures (vaccination, ventilation, testing) remain important.
How does duration affect baseline risk?
Longer exposure increases baseline risk. Consider splitting activities into shorter segments or taking breaks outdoors.
Should children wear the same masks?
Children benefit from well-fitting masks tailored to their face size. Consult pediatric guidance for age-specific recommendations.