Coronavirus Mask Calculator
Enter how many hours a day you wear a mask, how many days you want to plan for, your household size, and your mask type. The calculator works out the total number of masks you need, the minimum rotation set for reusable masks, and the total cost. Switch mask types to compare costs instantly.
How many masks do you actually need?
The answer depends on three things: how many hours a day you wear a mask, how long each mask lasts before it must be replaced or washed, and how many people you are buying for. For a single person wearing a surgical mask 4 hours a day for 30 days, that is 2 masks per day (one every 2 hours of wear), giving 60 masks for the month. Add a buffer of 10-20% and you should stockpile around 66-72 masks. The calculator handles all of this instantly when you change any input.
Cloth versus disposable masks
Cloth masks are the most cost-effective for long-term use. You buy a rotation set of five or more masks per person once and then wash them between use sessions. Surgical masks and disposable respirators (KN95, N95, N99) are single-use items that get discarded rather than laundered. Neither CDC nor WHO publishes an hours-based expiry for any of them: the rule is to replace a mask when it becomes damp, soiled or damaged, and to replace a respirator when it is wet, dirty, damaged, or no longer seals snugly. To turn that into a shopping list this calculator assumes 2 hours of wear per surgical mask, 16 hours per KN95 or N95, 24 hours per N99, and an 8-hour wear session per cloth mask before washing. Those assumptions drive the totals above, so change the hours-per-day figure if your own masks last longer or shorter. On filtration, NIOSH requires at least 95% efficiency for the N95 class and at least 99% for the N99 class; cloth and surgical mask performance varies widely by product and fit.
What is an emergency buffer and why does it matter?
Supply chain disruptions can make masks temporarily unavailable, exactly when demand is highest. Adding a 10-25% buffer to your calculated need means you have a safety cushion if a mask tears, you accidentally touch the filter surface, or you cannot restock on time. Public health agencies generally recommend keeping at least a 2-week supply on hand for households, and a 30-day supply if you have high-risk individuals at home.
How to wear and care for your mask correctly
A mask only works if it fits tightly over the nose and mouth with no gaps at the sides. Wash hands before putting on and after taking off a mask. Never touch the front filter surface. For cloth masks, launder at 60 C (140 F) or higher after each use session and allow 24 hours to dry fully before wearing again, which is the main reason a rotation set of at least 5 is advised. For disposables, fold the used mask inward (filter side in) before placing it in a sealed bag, then discard it. Do not reuse a disposable mask past its rated wear time even if it appears undamaged.
Mask types: protection, planning wear time and typical cost
| Mask type | Filtration | Planning wear time (this tool) | Reusable? | Typical cost each |
|---|---|---|---|---|
| Cloth | 50-70% (varies) | 8 h then wash | Yes (many times) | $2-5 |
| Surgical | 60-80% | 2 h | No | $0.20-0.50 |
| KN95 | 95% | 16 h | No | $1-2 |
| N95 | 95% | 16 h | No | $1.50-3 |
| N99 | 99% | 24 h | No | $2.50-5 |
Planning wear times are the stocking assumptions this calculator uses, counted in hours of actual use rather than clock hours. They are not published limits: CDC and WHO do not set an hours-based expiry for masks or respirators. CDC says to replace an N95 when it becomes wet, dirty or damaged or the straps no longer hold a snug fit, and WHO says to change a medical mask as soon as it becomes damp or soiled. The 95% and 99% figures are the NIOSH minimum filtration efficiencies for the N95 and N99 classes; the cloth and surgical ranges vary widely by product and fit.
Frequently asked questions
How long can you wear a surgical mask?
Neither CDC nor WHO sets a fixed number of hours. The rule from both is condition-based: a medical or surgical mask is single-use, and you replace it as soon as it becomes damp, visibly soiled, damaged, or hard to breathe through, because dampness from breathing reduces filtration efficiency. For stock planning this calculator assumes 2 hours of actual wear per surgical mask, which is a conservative working assumption rather than a published limit. At that assumption, 8 hours of wear a day works out to 4 masks per day. Adjust your own figure upward or downward if your masks last longer or shorter in practice.
Can I reuse an N95 or KN95 respirator?
NIOSH certifies N95 respirators for filtration efficiency, not for a number of hours, so there is no official wear-time rating. CDC says to replace an N95 when it becomes wet, dirty or damaged, or when the straps are stretched out and it no longer fits snugly against your face. In healthcare settings where reuse is being managed deliberately, CDC suggests limiting a respirator to about five donnings if the manufacturer gives no other guidance. This calculator uses 16 hours of cumulative wear per respirator as a stocking assumption only. Do not wash, heat-sterilise or spray disposable respirators: these processes damage the electrostatic filter material that does the work.
How many cloth masks do I need in my rotation?
You need at least 5 cloth masks per person. With a rotation set of 5, you can wear one while the others are being washed and dried. A wash-and-dry cycle typically takes around 24 hours, so having 5 masks means you will always have a clean one available. If you wear more than 8 hours per day you may need 6 or 7 to keep the rotation comfortable.
Are N95 masks better than KN95 masks?
Both filter at least 95% of airborne particles when worn correctly. N95 is the US standard (NIOSH-certified) and KN95 is the Chinese standard (GB 2626). They differ mainly in fit-test requirements and ear-loop vs head-strap design. When purchased from a verified manufacturer, either standard offers strong protection. Counterfeit KN95 masks are common, so buy from reputable suppliers and look for a GB 2626 marking on the mask itself.
How do I calculate masks for my whole family?
Multiply the per-person daily requirement by the number of people and by the number of days. For example, if each person needs 2 surgical masks per day and your household has 4 people planning for 30 days, you need 2 x 4 x 30 = 240 masks as a baseline. Add a 10% buffer to get 264 masks. The calculator above does this automatically when you set the household size.
Should I add a buffer to my mask supply?
Yes. A 10-20% buffer is a sensible precaution. Masks can tear, accidentally get contaminated, or become unavailable due to supply chain issues. Public health guidance generally recommends keeping a rolling 2-week household supply at minimum. If you have vulnerable household members, a 30-day buffer is prudent.