Water Purification Tablet Dosage Calculator

Select your tablet type and water volume to get the exact number of tablets needed, wait time, and how many people the treated water will serve.

Calculate tablet dosage

Select your purification product and enter the volume of water to treat.

Purification product

Each product has a different dose rate. Always verify against your package insert.

Water to treat

How much water and how clean it is. Cloudy water doubles the dose for most chemical tablets.

Water volume

Water clarity

Dosage Live

Add 5 tablets

For 5 liters with Aquatabs. Wait 30 minutes before drinking.

5 Tablets to add

30 min Wait before drinking

10 ½-liter servings

How to use this calculator

Select your purification product from the dropdown, each product has a specific dose rate per liter or quart. Enter the volume of water you need to treat and the unit (liters, gallons, or quarts). Select "cloudy" if the water appears turbid, which doubles the required dose. The result shows total tablets needed, recommended wait time before drinking, and how many half-liter servings the treated batch provides.

Tips for success

Filter cloudy or particulate water through a cloth, coffee filter, or pre-filter before adding tablets, turbidity dramatically reduces effectiveness.
Temperature matters: cold water (below 10°C / 50°F) slows chemical action. Extend wait times by 15–30 minutes in cold conditions.
Iodine tablets are not suitable for pregnant women, people with thyroid conditions, or shellfish allergies. Use NaDCC or chlorine dioxide instead.
Chlorine dioxide tablets (Micropur) are the most effective against Cryptosporidium, recommended for backcountry or unknown water sources.
Store tablets sealed and dry, exposure to air and moisture degrades them significantly. Check expiry dates annually.

Chemical tablets are a backup, not a primary filter. They kill bacteria and most viruses, but chlorine-based tablets do not eliminate Cryptosporidium. For truly unknown water sources, pair with a physical filter or use chlorine dioxide tablets and extend the wait time to 4 hours.

Comparison of common tablet types

NaDCC (Aquatabs, Katadyn MP1): Sodium dichloroisocyanurate. Fast-acting (30 min), low taste impact, no iodine. Most popular for emergency kits.
Iodine (Potable Aqua): Effective and inexpensive but leaves a noticeable taste. Potable Aqua PLUS includes a neutralizer tablet to improve taste. Not for long-term use.
Chlorine dioxide (Micropur MP1): Broadest spectrum, the only tablet type effective against Cryptosporidium. Requires a 4-hour wait for full effectiveness. Best for unknown backcountry water.

FAQ

How many tablets should I stockpile for a 72-hour kit?

Plan for 1 gallon (3.8L) of water per person per day. Aquatabs treat 1L per tablet, so for a family of 4 over 3 days, you'd need 46 tablets at minimum. Buy a 50–100 tablet pack and replace annually. They're inexpensive, no reason to cut it close.

Can I use pool shock (calcium hypochlorite) instead of tablets?

Yes. Pool shock (78%+ calcium hypochlorite) can purify water in emergencies: dissolve 1 teaspoon in 2 gallons of water to create a concentrate, then add 1 part concentrate to 100 parts water. It's far more economical for large quantities. Tablets are better for portability and single-batch use.

Do purification tablets remove heavy metals or chemicals?

No. Chemical tablets only disinfect biological pathogens (bacteria, viruses, and some protozoa). They do not remove heavy metals, pesticides, nitrates, or chemical contaminants. For chemical contamination, activated carbon filtration is required.

What's the shelf life of purification tablets?

Properly sealed: Aquatabs and NaDCC tablets last 3–5 years. Iodine tablets last 4 years sealed, but degrade quickly once opened. Micropur chlorine dioxide tablets are good for 4–5 years sealed. Always store in a cool, dark, dry place and check expiry dates when rotating your kit.