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 just wash them after every 8 hours of wear. Surgical and disposable respirator masks (KN95, N95, N99) are discarded after their rated wear time. Surgical masks typically need replacing every 2 hours of use, making them expensive over weeks or months. N95 and KN95 respirators last up to 16 hours of cumulative wear and filter at least 95% of airborne particles, making them a good middle ground between cost and protection. N99 respirators offer the highest filtration but are also the most expensive per unit.
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, wear time and typical cost
| Mask type | Filtration | Max wear time | 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 |
Wear-time limits are per hours of actual use, not clock hours. CDC guidance as of 2024.
Frequently asked questions
How long can you wear a surgical mask?
According to CDC guidance, a surgical (procedural) mask should be replaced after approximately 2 hours of continuous wear, or sooner if it becomes damp, visibly soiled, or hard to breathe through. Dampness from breathing reduces its filtration efficiency significantly. If you wear one for 8 hours a day you will need roughly 4 masks per day.
Can I reuse an N95 or KN95 respirator?
N95 and KN95 respirators are rated for up to 16 hours of cumulative wear time before the filtration material degrades. You can wear the same respirator across multiple short sessions, tracking the total time, then discard it when you reach 16 hours. 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.