Keep your hot tub at 50–100 ppm hydrogen peroxide
A hot tub holds a few hundred gallons, so the right amount is measured in ounces, not gallons. Here's how to get it right with 12% or 35%.
Hot tub owners who run their tub on hydrogen peroxide hold it between 50 and 100 parts per million (ppm), the same range as a pool. The difference is scale: a hot tub holds a few hundred gallons instead of tens of thousands, so the amount you add is measured in ounces. You need three numbers: how much water your tub holds, the strength of the peroxide you pour in, and what your test strip reads right now. The calculator below works it out for 12% or 35% hydrogen peroxide.
Hot tub dose chart
Total amount to reach each level from a 0 ppm reading.
35%Hydrogen peroxide| Tub size | 50 ppm | 80 ppm | 100 ppm | +10 ppm |
|---|---|---|---|---|
| 250 gal2–3 seats | 4.0 | 6.5 | 8.1 | 0.8 |
| 350 gal4–5 seats | 5.7 | 9.1 | 11.3 | 1.1 |
| 450 gal6–7 seats | 7.3 | 11.7 | 14.6 | 1.5 |
| 550 gal8+ seats | 8.9 | 14.2 | 17.8 | 1.8 |
12%Hydrogen peroxide| Tub size | 50 ppm | 80 ppm | 100 ppm | +10 ppm |
|---|---|---|---|---|
| 250 gal2–3 seats | 12.8 | 20 | 26 | 2.6 |
| 350 gal4–5 seats | 17.9 | 29 | 36 | 3.6 |
| 450 gal6–7 seats | 23 | 37 | 46 | 4.6 |
| 550 gal8+ seats | 28 | 45 | 56 | 5.6 |
Test before you add. Already have some in the tub? Use the green +10 ppm column for each 10 ppm you need. 1 fl oz is about 30 mL; 8 fl oz is 1 cup. Get test strips →Hot Tub Peroxide Calculator
Enter your hot tub's gallons, then see how much 12% or 35% hydrogen peroxide brings it into the 50–100 ppm range. Small tub, small amounts: we show it in fluid ounces.
How many gallons does your hot tub hold?
Use the number from your owner’s manual. Don’t have it handy? Tap a typical size to start.
Typical sizes fill in the middle of each range. Seat count is only a rough guide, so your manual’s number is always better. Inflatable and plug-and-play tubs often hold 150–250 gallons.
Choose your hydrogen peroxide
Both reach the same ppm. The difference is how much you pour.
What does your test strip read?
Dip a strip and match the color. Fresh fill? Leave it at 0.
Hydrogen Peroxide Test StripsRead 0–100 ppm · 50 strips per bottle
Free PDF guide
Take the hot tub peroxide guide with you
- Dose chart, 150–600 gal
- Test strip guide
- Printable hot tub log
9 pages · by email (and text, if you like)
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Why Hot Tubs Are Different
The target range is the same as a pool, but a few things about a hot tub change how you get there and how often you check.
Small amounts
A few ounces makes a big difference in a few hundred gallons. Measure every dose with a marked cup; don’t pour straight from the jug.
Hot water
Hydrogen peroxide breaks down faster in warm water, so your reading drops quicker than in a pool.
More people per gallon
A full tub of soakers in a small volume uses peroxide up faster. Test before each soak.
A cover on top
Take the cover off while you add peroxide and leave it off for a while afterward.
What 50–100 ppm Means in a Hot Tub
100 ppm
is 0.01% hydrogen peroxide by weight
~13 fl oz
of 35% brings a 400-gallon tub from 0 to 100 ppm
~41 fl oz
of 12% brings a 400-gallon tub from 0 to 100 ppm
Parts per million describes how much hydrogen peroxide is in the water by weight. A bottle of 35% is 350,000 ppm, so a little goes a long way in a small tub. The calculator works by weight: it figures out how many grams your tub needs to rise from your current reading to your target, then converts that to the fluid ounces of 12% or 35% solution that contain it.
How Many Gallons Does Your Hot Tub Hold?
The best number is the one from your owner’s manual. You’ll also often find it on the spec label inside the equipment access panel, or on the manufacturer’s website by model name. If you can’t find it, these ranges are a reasonable starting point:
200–300 gal
2–3 seats
300–400 gal
4–5 seats
400–500 gal
6–7 seats
500+ gal
8+ seats
Seat count is only a rough guide. Two tubs with the same number of seats can differ by 100 gallons or more depending on the seat layout and depth. Inflatable and plug-and-play tubs often hold 150–250 gallons. If you’re estimating, start at the low end of the range, add three quarters of the amount, and let your test strip tell you how much more you need.
Before You Start
Test strips
Have hydrogen peroxide test strips that read 0–100 ppm.
Goggles & gloves
Splash-proof goggles and nitrile or butyl rubber gloves.
A measuring cup
A clean plastic cup with ounce markings, used only for peroxide. Never metal.
Read the SDS
Check your equipment
Ask your hot tub’s maker about hydrogen peroxide at 50–100 ppm with your shell, heater, pump, cover and headrest pillows.
Ozonators & UV
If your tub has an ozonator, UV light or another built-in water system, check with the manufacturer before adding peroxide.
Cartridges & floaters
Take out bromine or chlorine floaters and any cartridges or mineral sticks that work alongside them.
This guide is for residential hot tubs. Public and commercial spas follow the water-treatment requirements set by their local health department.
Switching From Bromine or Chlorine? Start With Fresh Water
Bromine and chlorine compete with hydrogen peroxide. When they meet in the water, they react with and use up each other, so anything left in the tub eats into the peroxide you add. Bromine is especially stubborn in hot tubs because it builds up in the water over time. The cleanest way to switch is to drain, clean and refill, which most hot tubs need every few months anyway.
- Stop adding bromine or chlorine and take out any floaters or cartridges.
- Drain the tub, rinse or replace the filter as your manufacturer recommends, and wipe down the shell.
- Refill with fresh water and bring it up to temperature.
- Confirm bromine and chlorine read zero with a bromine or chlorine test strip, then add peroxide using the calculator.
Can’t drain right now? Let the bromine or chlorine fall to zero first, then add peroxide in stages and retest after each one. Expect to need more than the calculator shows until it’s used up.
Never add hydrogen peroxide and bromine or chlorine at the same time, and never mix them in a cup or container.
How to Add Hydrogen Peroxide to Your Hot Tub
- Cover offOpen the cover and leave it open while you add peroxide and for a little while after.
- Jets runningCirculation on so the peroxide mixes in right away. Turn the air blower off to limit splashing.
- Pour slowly near a jetMeasure into a clean plastic cup and pour close to the water. Keep it off the shell, cover and headrest pillows (see the red marker).
- Wait, then testRun the jets 15 to 20 minutes, then dip a test strip away from where you poured.
- Test first. Dip a test strip and note your current reading.
- Work out your amount with the dose chart or calculator above, using that reading.
- Everyone out. Nobody in the tub, including pets, while you add peroxide.
- Take the cover off and fold it out of the way.
- Turn on the jets so the water is circulating. Turn the air blower off to limit splashing.
- Put on goggles and gloves.
- Measure about three quarters of the amount into a clean plastic measuring cup.
- Pour slowly and close to the water near a jet so it mixes in right away. Keep it off the shell, the cover and the headrest pillows, where concentrated peroxide can bleach or damage surfaces.
- Rinse the cup and any drips with plenty of water.
- Run the jets for 15 to 20 minutes with the cover off, then test again and top up in small amounts until the strip reads in your target range.
- Leave the cover off a little longer, then close it. Soak once the strip reads 50–100 ppm.
How to Use Hydrogen Peroxide Test Strips
Your test strip is how you avoid both underdosing and overdosing. The strips are sensitive: they change color across roughly 10 to 100 ppm, which is exactly the range a hot tub runs in. In a small tub the level can move quickly, so get in the habit of testing before every soak.
Illustration only. The pad darkens as the peroxide level rises; always match against the color chart printed on your strip bottle.
Hydrogen Peroxide Test Strips0–100 ppm · 50 strips per bottle · keep the cap tight and the strips dry
Keeping Your Hot Tub at 50–100 ppm
Hydrogen peroxide breaks down into water and oxygen over time, and it goes faster in a hot tub than in a pool. These speed it up:
Water temperature
The warmer the water, the faster the level drops.
Number of soakers
More people and longer soaks use it up quicker.
Lotions & oils
Body lotion, sunscreen and hair products add to the load. A quick rinse before soaking helps.
Debris
Leaves and organic matter in the water.
- Test before every soak. In a small tub the level can drop noticeably in a day or two.
- Top up before you hit 50 ppm. Use the +10 ppm column in the dose chart or the calculator.
- Keep a simple log of the date, reading and amount added so you learn how fast your tub uses it.
- Look after the filter by rinsing or replacing it on the schedule your manufacturer recommends.
- Drain and refill on schedule. When you refill, start over from a zero reading.
- Keep up your normal water-balance testing, such as pH and alkalinity, as your hot tub maker recommends.
12% or 35%: Which Should You Use?
35%Hydrogen peroxide- About 13 fl oz brings a 400-gallon tub to 100 ppm
- A 32 oz bottle covers many top-ups
- More concentrated, so measure carefully and handle with extra care
12%Hydrogen peroxide- About 41 fl oz brings a 400-gallon tub to 100 ppm
- Bigger pours make small top-ups easier to measure
- Less concentrated, but still needs goggles and gloves
Both reach the same ppm in your tub; the difference is how much you measure and pour. Going through a lot? Both also come in larger 35% sizes and 12% gallons. Check each product page for shipping options, since container size and concentration affect how it ships.
Handling and Storage
Protect eyes & skin
Wear splash-proof goggles and chemical-resistant gloves whenever you handle concentrated peroxide.
Original container
Tightly closed and upright, in a cool, dark, ventilated place out of direct sun. Not on top of a warm hot tub.
Store it separately
Away from bromine, chlorine, acids, metals and anything flammable.
No pouring back
Never return unused peroxide to the bottle, and never use metal cups or scoops.
Lock it up
Keep it away from children and pets.
If it splashes
Eyes: rinse with clean water for at least 15 minutes and get medical help. Skin: rinse thoroughly. Follow the SDS first-aid section.
35% Food Grade Hydrogen Peroxide 32 oz
35% Food Grade Hydrogen Peroxide 1 Gallon
12% Food Grade Hydrogen Peroxide Solution 32 oz
12% Food Grade Hydrogen Peroxide Solution 1 Gallon
Hydrogen Peroxide Test StripsFrequently Asked Questions
How much 35% hydrogen peroxide do I need for my hot tub?
About 13 fluid ounces for a 400-gallon tub to go from 0 to 100 ppm, or about 10 fluid ounces to reach 80 ppm. That works out to roughly 3.2 fl oz per 100 gallons for 100 ppm. Use the calculator for your exact tub size and current reading.
How much 12% hydrogen peroxide do I need?
About 41 fluid ounces for a 400-gallon tub to go from 0 to 100 ppm, or about 33 fluid ounces to reach 80 ppm. That’s roughly 10 fl oz per 100 gallons for 100 ppm.
How often should I test?
Before every soak, and every day or two when the tub is in regular use. Hot water and a small volume mean the level moves faster than in a pool.
There’s still bromine or chlorine in my tub. What should I do?
They compete with hydrogen peroxide and use it up, so some of the peroxide you add goes into reacting with them instead of raising your reading. The cleanest fix is to drain, clean and refill. If you can’t, let it fall to zero, then add peroxide in stages and retest until the strip holds in the 50–100 ppm range.
Can I use hydrogen peroxide with an ozonator or UV system?
Check with your hot tub’s manufacturer first. Built-in water systems vary, and they can tell you whether hydrogen peroxide at 50–100 ppm is compatible with yours.
My test strip didn’t change color right after I added peroxide. Why?
A strip dipped into concentrated peroxide, or into the spot where you just poured, gets overloaded and burns out, showing no color at all. Run the jets for 15 to 20 minutes, then test a few inches down, away from the jets.
What if my reading is over 100 ppm?
Stop adding peroxide, leave the cover off and run the jets. The level comes down on its own as the peroxide breaks down, which happens fairly quickly in warm water. Retest before soaking and wait until the strip reads 100 or below.
Can I add peroxide while people are in the tub?
No. Everyone stays out while you add it, and until the water has circulated and a test strip reads within 50–100 ppm.
Is the calculator exact?
The chemistry is exact, but tub volumes are estimates and strips read in steps. That’s why the calculator has you add about three quarters first, then retest and top up.
Have a pool too? Our hydrogen peroxide pool guide has a calculator and dose charts for 5,000 to 50,000 gallons.
Free PDF guide
Take the hot tub peroxide guide with you
- Dose chart, 150–600 gal
- Test strip guide
- Printable hot tub log
9 pages · by email (and text, if you like)
Check your inbox
We sent a download link to . It can take a minute to arrive. Don't see the email? Check your spam or promotions folder.
Disclaimer
Information only, used at your own risk. This page, the dose chart and the calculator are general information provided for convenience. They are not professional, engineering, medical or legal advice. Results are estimates that depend on the measurements, test readings and other information you enter, and on conditions we cannot see or control. You are solely responsible for deciding whether and how to use hydrogen peroxide in your hot tub, and for every amount you add.
No claims about water treatment. This guide explains how to reach and hold a hydrogen peroxide concentration. It makes no claim that hydrogen peroxide sanitizes or disinfects water or controls any organism, and our products are not sold as registered spa or pool sanitizers. Public and commercial spas must follow the requirements of their local health authority.
Equipment, surfaces and property. Hydrogen peroxide is a strong oxidizer. Before use, confirm compatibility with the manufacturer of your hot tub, including the shell, heater, pump, jets, filter, cover, headrest pillows, ozonator, UV system and any other equipment. We are not responsible for damage to hot tubs, equipment, covers, pillows, surfaces, finishes, decks, clothing or any other property, or for voided warranties, resulting from the use or misuse of hydrogen peroxide or of the information on this page.
Skin sensitivity and soaking. Some customers with sensitive skin have told us they notice a slight tingling at levels around 120 ppm and above. This is customer feedback, not a tested threshold, and sensitivity varies from person to person. If anyone feels irritation, have them get out and rinse with fresh water, keep everyone out until the level comes down, and seek medical advice if irritation continues. Follow your hot tub manufacturer’s guidance on water temperature and soak times, and anyone with a health condition or who is pregnant should talk to a doctor before using a hot tub.
Handling. Concentrated hydrogen peroxide can cause serious burns to skin and eyes. Always follow the product label and Safety Data Sheet, wear protective equipment, and keep it away from children and pets.
Limitation of liability. To the fullest extent permitted by law, Bulk Peroxide and its owners, employees and affiliates disclaim all warranties, express or implied, regarding this information, and are not liable for any direct, indirect, incidental, consequential or other damages, including personal injury, property damage or loss, arising from the use of this page, the calculator, or our products in a hot tub. By using this information you accept these terms. Nothing here limits any rights you have that cannot be limited under applicable law.