Mask vs No Mask Calculator — Estimated Risk Reduction
Estimate how much a mask reduces your exposure to airborne particles depending on what you and the infectious source both wear. Compares no mask, cloth, surgical, KN95, and N95 respirators using published filtration data.
Mask worn by you (the wearer)
Mask worn by infectious source
Compared to both parties wearing no mask — a modelled estimate, not a clinical guarantee
- 1
Source control (source mask)
s = 50 % = 0.5Fraction of emitted particles blocked by the infectious source's mask. - 2
Wearer filtration (your mask)
w = 72 % = 0.72 - 3
Residual fraction after source mask
1 − 0.5 = 0.5 - 4
Relative risk = (1−s) × (1−w)
0.5 × 0.28 = 0.14 - 5
Risk reduction = (1 − relative risk) × 100
(1 − 0.14) × 100 = 86Percentage reduction in aerosol exposure compared to both parties wearing no mask.
How does this calculator work?
Risk reduction = 1 − (1 − source control) × (1 − wearer filtration). An N95 (≥95% filtration) paired with a source also wearing N95 gives ≈99% risk reduction. Surgical masks on both parties give ≈86%. Even one party masking provides meaningful protection. Results are modelled estimates — fit and ventilation matter.
Formula
How this is calculated
Masks reduce aerosol transmission through two mechanisms: source control (the infected person's mask traps outgoing particles) and wearer protection (your mask filters incoming particles). When both mechanisms are active, they multiply: if the source's mask removes 50% of emitted particles, and your mask filters 72% of the remainder, only 14% of the original aerosol load reaches you — a relative risk of 0.14, or an 86% risk reduction compared to both parties being unmasked.
Filtration figures are particle-level estimates from published laboratory and field studies. Cloth masks (single layer) block roughly 20% of particles; 2–3 layer cloth approximately 40%; surgical/procedure masks around 72%; KN95 around 90%; properly fitted N95 respirators around 95%. Source-control values — how effectively the mask reduces what an infected person emits — are typically 50–80% of the filtration figure, as outward breath velocity varies. Real-world protection depends heavily on fit, seal, how long the mask has been worn, and room ventilation. An ill-fitting N95 may perform no better than a surgical mask.
This calculator provides a modelled estimate for educational purposes and is not medical advice. The same model was used qualitatively in publications such as Lindsley et al. (2021) in JAMA Internal Medicine. Consult current public-health guidelines for the appropriate mask to wear in a given setting.
Frequently asked questions
Laboratory studies suggest surgical masks filter roughly 60–80% of aerosol-sized particles when worn snugly. The source control benefit (protecting others) is typically around 50%. When both parties wear surgical masks the combined estimated risk reduction is around 85% compared to neither wearing one.
A properly fitted N95 respirator filters ≥95% of airborne particles vs roughly 72% for a surgical mask. The gap is significant for prolonged close exposure in poorly ventilated spaces, but a loose or incorrectly worn N95 can perform as poorly as a cloth mask. Fit-testing and a proper seal are crucial.
Yes, but mutual masking is substantially more effective. A source wearing a mask that reduces emitted particles by 50% already halves the dose before your own mask acts on it. The best outcome comes from both parties masking to the highest level practical for the setting.
Also known as
TG we-Calculate Editorial Team. (2026). Mask vs No Mask Calculator — Estimated Risk Reduction [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/mask-vs-no-mask-calculator
TG we-Calculate Editorial Team. "Mask vs No Mask Calculator — Estimated Risk Reduction." TG we-Calculate. 2026. https://we-calculate.com/calculator/mask-vs-no-mask-calculator.
TG we-Calculate Editorial Team, "Mask vs No Mask Calculator — Estimated Risk Reduction," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/mask-vs-no-mask-calculator
@misc{wecalculate_mask_vs_no_mask_calculator, title = {Mask vs No Mask Calculator — Estimated Risk Reduction}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/mask-vs-no-mask-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?