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Teeth Whitening Strength Converter

Enter the active ingredient and the percentage on your whitening product's label. See its hydrogen peroxide equivalent, how that strength fits the rules in the US, EU, UK, Canada and Australia, and what to expect.

Example shown. Enter what your product's label says.

Look for "hydrogen peroxide" or "carbamide peroxide" next to the strength or in the ingredient list.

%

The number before the % sign, for example 10, 16 or 35.

Product type

Rules differ by country. We list only places whose rules we could check.

Hydrogen peroxide equivalent

Trays with gel

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Rules where you live

This strength in each place

PlaceStatus

What to expect

This product type
Sensitivity
Gums
Sore or white gums usually come from gel touching the gums. With trays, irritation most often comes from a tray that doesn't fit well. It's usually short-lived.
How long it lasts
Sources differ. In a 2-year trial, results from both in-office (35% hydrogen peroxide) and at-home (16% carbamide peroxide) whitening showed no significant fade. Another trial saw a slight fade by 9 months. The NHS says results may last around 3 years if you follow your dentist's advice, but teeth can restain within a month if you keep up staining foods and drinks.
How often
No guideline sets a fixed schedule. Follow the product's directions and whiten again only when the color has faded. Overuse can damage enamel or gums.

See a dentist before you whiten if:

  • you're under 18, pregnant or breastfeeding
  • you have gum disease, tooth decay or broken or leaky fillings
  • one tooth has turned darker than the others
  • you have crowns, veneers, bonding or implants where they show: they won't change color

Common strengths compared

Common label strengths, their hydrogen peroxide equivalent, and their status in the EU and UK, Canada and Australia. In the US we found no federal percentage limit.
On the labelHydrogen peroxideEU & UKCanadaAustralia

Hydrogen peroxide figures use Health Canada's factor of 0.361 for carbamide peroxide. In the US we found no federal percentage limit, so it has no column. A highlighted row matches your entry.

Carbamide peroxide vs hydrogen peroxide: how to convert

Multiply the carbamide peroxide percentage by 0.361 to get the hydrogen peroxide equivalent. Carbamide peroxide is hydrogen peroxide bound to urea. In contact with water it breaks apart, and about a third of its weight is released as hydrogen peroxide, the part that does the bleaching.

On the labelHydrogen peroxide equivalent
10% carbamide peroxideabout 3.6%
16% carbamide peroxideabout 5.8%
22% carbamide peroxideabout 7.9%
35% carbamide peroxideabout 12.6%

Health Canada publishes the 0.361 factor, and it matches the European figures (10% carbamide peroxide = 3.6%; 6% hydrogen peroxide = 16.62% carbamide peroxide). Some sources round it to "about a third" or say 10% equals "about 3%". The differences are only rounding.

Not every whitening product contains peroxide. PAP (phthalimidoperoxycaproic acid) is a non-peroxide bleaching agent, so it has no hydrogen peroxide equivalent. Most whitening toothpastes work mainly by polishing off surface stains.

What strength of hydrogen peroxide is safe?

There's no single safe number: the rules depend on where you live. Each country draws its lines in a different place:

PlaceKey lineAbove that lineHighest allowed
European Union0.1% hydrogen peroxideOnly through a dentist, who does the first use; not for anyone under 186%
United Kingdom0.1% hydrogen peroxideOnly through a dental professional; not for anyone under 18 unless it treats disease6%, except to treat or prevent disease
Canada3% hydrogen peroxideThe maker must send Health Canada a clinical study on peroxide in salivaNo limit set in the guidance
Australia6% hydrogen peroxide or 18% carbamide peroxideRegistered dental practitioners only–
United StatesNo federal limit found––

EU safety experts concluded that 0.1% is safe for products sold freely. They judged up to 6% possibly safe if a dentist checks your mouth first and use is limited, and above 6% not safe for consumers. In the US, the FDA said in 2014 that most peroxide whiteners would meet the definition of a cosmetic, and we found no federal percentage limit. Store products there are weaker than dentist products, and dentist take-home gels are typically 10% to 38% carbamide peroxide.

Strength isn't the whole story. How long the gel touches your teeth, how often you use it and how well it stays off your gums all matter too.

Is teeth whitening safe for enamel?

Used as directed, peroxide whitening is considered safe and doesn't cause lasting damage to the tooth. That's the conclusion of the American Academy of Pediatric Dentistry and of a 2014 research review. Some studies found the enamel surface can become slightly rougher or softer. Overuse is the real risk: the ADA warns it can damage enamel or gums, and overtreatment has been shown to harm tooth structure.

Acidity matters too: in Canada, whitening products must have a pH of at least 4.

Why teeth get sensitive after whitening, and what helps

Peroxide passes through the enamel to the dentin underneath and briefly irritates the tooth's nerve. It's the most common side effect. Studies report it in anywhere from 8% to 66% of people, often in the first days. Pooled data from 11 trials found about 51% of people had some sensitivity with at-home whitening and 63% with in-office whitening. It's usually mild and stops after treatment ends.

What helps:

  • Use a lower strength. In a 2025 review of at-home trials, 20–22% carbamide peroxide gels had about twice the sensitivity risk of 10–11% gels.
  • Take a break. The ADA says you can stop, then try again later.
  • Desensitizing toothpaste helped in some studies but not others. Bleaching gels with a desensitizer added didn't lower the risk.
  • Pain relievers taken beforehand need more research, the ADA says.

Sensitivity usually lasts no more than a few days. If it lasts longer, see a dentist. The Tooth Sensitivity Quiz helps you sort out other causes.

How long does teeth whitening last?

Usually months to a few years, depending mostly on your habits. In one 2-year trial, people whitened at the dentist or at home kept their shade with no significant fade. Another trial found a slight fade by 9 months. The NHS says results may last around 3 years if you follow your dentist's advice. Keep up staining foods and drinks like coffee, tea and red wine, and teeth can restain within a month. The Teeth Stain Risk Quiz shows which habits matter most for you.

How often can you whiten your teeth?

No guideline sets a fixed schedule, so whiten again only when the color has faded and follow the directions. Overuse can damage enamel and gums. In the EU and UK, each new course of a stronger product starts with a visit to a dental professional. Health Canada requires a warning to ask your oral health professional before long-term use.

At-home vs professional whitening

At-home products are weaker and slower; in-office whitening is stronger and faster. The main types:

  • Whitening toothpaste removes surface stains only.
  • Strips and paint-on gels or pens are store products, often used twice a day for about 2 weeks.
  • Trays with gel from a dentist are custom-fitted, so the gel stays on your teeth and off your gums. They're worn a few hours a day or overnight.
  • In-office whitening uses about 25% to 35% hydrogen peroxide, with your gums shielded, often in one visit.

A 2025 review found at-home whitening caused milder sensitivity than in-office whitening, with similar or better color change, though the evidence was low certainty. Choosing a gel strength: start low. Lower strengths cause less sensitivity, and reviews haven't shown that stronger gels give better results in the end. Pediatric dentists also point to using the lowest strength that works.

Can you whiten crowns, veneers, bonding or implants?

No. Whitening only lightens natural teeth. Crowns, veneers, tooth-colored fillings and bonding, bridges, implant crowns and dentures keep their color. If you whiten natural teeth next to them, they may no longer match. Before whitening, a dentist can check which dental work shows and what replacing it to match might cost. See how long dental work lasts if older work is due for replacement.

How this tool works

  1. Conversion. It multiplies the label percentage by Health Canada's factor: 1 for hydrogen peroxide, 0.361 for carbamide peroxide, 0.472 for calcium peroxide, 0.349 for zinc peroxide and 0.602 for magnesium peroxide. It doesn't convert PAP, sodium perborate or products without peroxide.
  2. Rounding. Results are rounded to two decimals, as Health Canada asks for peroxide concentrations (three decimals below 1%). The tool compares that rounded number with each limit, so the number you see and the verdict always agree.
  3. Rules. EU and UK limits use the hydrogen peroxide equivalent. Canada's 3% trigger does too. Australia's rules are written for each ingredient (6% hydrogen peroxide, 18% carbamide peroxide), so the tool checks the label number there. Note that 18% carbamide peroxide is about 6.5% hydrogen peroxide: legal for consumers in Australia, but over the EU limit.
  4. Expectations. Sensitivity numbers come from pooled clinical trials, not your own teeth.

It can't tell you whether whitening is right for you. Rules change, so check with a dentist before using anything strong.

Frequently asked questions

Is 6% hydrogen peroxide safe for teeth?
It depends on who is using it and how. In the EU and UK, 6% is the most allowed, and only through a dental professional who checks your mouth first and does the first use. EU safety experts judged products above 6% not safe for consumers. In Australia, products up to 6% can be sold directly to consumers. Sensitivity is common at any strength, and stronger at-home products cause more of it.
What strength of carbamide peroxide should I use?
Start low. Dentist take-home gels typically range from 10% to 38% carbamide peroxide, which is about 3.6% to 13.7% hydrogen peroxide. In a 2025 review of at-home trials, 20–22% gels had about twice the sensitivity risk of 10–11% gels, and reviews haven't shown that stronger gels give better results in the end. Your dentist can choose a strength for your teeth.
Does whitening toothpaste whiten teeth?
It removes surface stains, mainly with mild abrasives, but it doesn't change the tooth's own color the way peroxide bleaching does. The ADA suggests one with the ADA Seal for stain removal. You can compare abrasivity in the Toothpaste RDA Chart.
Can teenagers whiten their teeth?
Usually not with strong products. In the EU and UK, products above 0.1% hydrogen peroxide can't be used on anyone under 18 (the UK allows an exception only to treat or prevent disease), and the NHS doesn't whiten teeth for anyone 17 or younger. US pediatric dentists say teens using home products should be supervised by an adult, and they discourage cosmetic whitening while baby teeth are still present. Health Canada requires a label warning that peroxide products aren't recommended for children under 12.
Why do in-office gels go up to 35% if the EU limit is 6%?
Because the rules differ. In the EU and UK, nothing above 6% hydrogen peroxide is allowed for whitening, even at a dentist. In Australia, stronger gels are allowed, but only for registered dental practitioners. In the US we found no federal percentage limit. Where it's allowed, in-office whitening generally uses about 25% to 35% hydrogen peroxide, with the gums shielded first.

Sources

  1. Health Canada. Evidence of safety requirements for tooth whitening products containing peroxide and peroxide-generating compounds. published September 2024, modified 2025-08-12. Conversion factors (carbamide/urea peroxide 0.361), the 3% clinical-study trigger, pH of at least 4, label warnings. Accessed October 26, 2026.
  2. European Commission, Scientific Committee on Cosmetic Products and Non-Food Products (SCCNFP). Clarification of the Opinion concerning Hydrogen (carbamide) peroxide in Tooth Whitening Products. opinion of 1999. 3.6% hydrogen peroxide = 10% carbamide peroxide. Accessed October 26, 2026.
  3. Dental Council (Ireland). Tooth Whitening – Guidance to the Dental Profession. effective 31 October 2012. 6% hydrogen peroxide is the equivalent of 16.62% carbamide peroxide. Accessed October 26, 2026.
  4. Dental Council and Irish Medicines Board. Notice to Dental Practitioners: Hydrogen Peroxide in Tooth Whitening Products. September 2012. Summary of the EU rules from Directive 2011/84/EU and the SCCP opinion. Accessed October 26, 2026.
  5. EUR-Lex (Official Journal of the European Union). Council Directive 2011/84/EU of 20 September 2011 (amending Annex III of Cosmetics Directive 76/768/EEC). 2011. Listed as no longer in force since 2013; its rules carried over into the EU Cosmetics Regulation (EC) No 1223/2009. Accessed October 26, 2026.
  6. European Commission (summary of the SCCP 2007 opinion). Details on Tooth Whiteners & Oral Hygiene Products containing hydrogen peroxide. 2007. Sections 1, 3, 5 and 6: carbamide peroxide contains about 35% hydrogen peroxide; in-office 25–35%; sensitivity in up to two-thirds; above 6% not considered safe. Accessed October 26, 2026.
  7. General Dental Council (UK). Tooth whitening position statement. 11 July 2016. Accessed October 26, 2026.
  8. NHS. Teeth whitening. reviewed 19 August 2025. Accessed October 26, 2026.
  9. Australian Dental Association. Policy Statement 2.2.8 - Teeth Whitening (Bleaching) By Persons other than Dental Practitioners. amended 24 April 2026. Poisons Standard: 3–6% hydrogen peroxide and 9–18% carbamide peroxide are Schedule 5; above 6% / 18% dental practitioners only (Schedule 10). Accessed October 26, 2026.
  10. Federal Register of Legislation (Australia). Therapeutic Goods (Poisons Standard—October 2026) Instrument 2026. 2026. Current Poisons Standard. Schedule 5: hydrogen peroxide more than 3% up to 6%, carbamide peroxide more than 9% up to 18% (3% or less and 9% or less are not scheduled). Schedule 10: teeth whitening preparations above 6% hydrogen peroxide or 18% carbamide peroxide, except those supplied solely by registered dental practitioners. Accessed October 26, 2026.
  11. Federal Register of Legislation (Australia). Poisons Standard Amendment No. 1 of 2013. 2013. Created the dental-practitioner-only entries for teeth whitening preparations above 18% carbamide peroxide or 6% hydrogen peroxide. No longer in force as a separate instrument; carried into later Poisons Standards. Accessed October 26, 2026.
  12. Regulatory Affairs Professionals Society (RAPS). Are Products Used to Whiten Your Teeth Drugs or Cosmetics? FDA Weighs in. 23 April 2014. Reports the FDA's response to the ADA's 2009 petition. Accessed October 26, 2026.
  13. American Dental Association. Whitening (Oral Health Topics). updated August 16, 2022. Accessed October 26, 2026.
  14. American Dental Association (MouthHealthy). Teeth Whitening. Accessed October 26, 2026.
  15. American Academy of Pediatric Dentistry. Policy on the Use of Dental Bleaching for Child and Adolescent Patients. latest revision 2023. Accessed October 26, 2026.
  16. Carey CM. Journal of Evidence-Based Dental Practice. Tooth Whitening: What We Now Know. 2014. Accessed October 26, 2026.
  17. Llena C, Saenz L, Ghilotti J, Folguera S, Melo M. Journal of Functional Biomaterials. Phthalimidoperoxycaproic Acid (PAP) Versus Peroxides and Impact on Dental Enamel After Whitening Treatment: An In Vitro Study. 2026. Accessed October 26, 2026.
  18. Rezende M, Loguercio AD, Kossatz S, Reis A. Journal of Dentistry. Predictive factors on the efficacy and risk/intensity of tooth sensitivity of dental bleaching: A multi regression and logistic analysis. 2016. Sensitivity 51% at-home, 62.9% in-office (11 trials). Accessed October 26, 2026.
  19. de Geus JL, Martins A, Reis A, Rezende M. Operative Dentistry. At-home vs In-office Bleaching: An Updated Systematic Review and Meta-analysis. 2025. Accessed October 26, 2026.
  20. Terra RMO, Favoreto MW, Morris T, Loguercio AD, Reis A. Journal of Dentistry. Effect of at-home bleaching agents and concentrations on tooth sensitivity: A systematic review and network meta-analysis. 2025. 20–22% vs 10–11% carbamide peroxide: risk ratio 2.0; 14–16% vs 2–4% hydrogen peroxide: 2.9. Accessed October 26, 2026.
  21. Eachempati P, Kumbargere Nagraj S, Kiran Kumar Krishanappa S, Gupta P, Yaylali IE. Cochrane Database of Systematic Reviews. Home-based chemically-induced whitening (bleaching) of teeth in adults. 2018. Accessed October 26, 2026.
  22. Tay LY, Kose C, Herrera DR, Reis A, Loguercio AD. American Journal of Dentistry. Long-term efficacy of in-office and at-home bleaching: a 2-year double-blind randomized clinical trial. 2012. Accessed October 26, 2026.
  23. Fernández E, Bersezio C, Bottner J, et al. Operative Dentistry. Longevity, Esthetic Perception, and Psychosocial Impact of Teeth Bleaching by Low (6%) Hydrogen Peroxide Concentration for In-office Treatment: A Randomized Clinical Trial. 2017. Accessed October 26, 2026.
  24. Rezende M, Coppla FM, Chemin K, et al. Operative Dentistry. Tooth Sensitivity After Dental Bleaching With a Desensitizer-containing and a Desensitizer-free Bleaching Gel: A Systematic Review and Meta-analysis. 2019. Accessed October 26, 2026.
  25. Cabral AEA, Lourenço MAG, de Medeiros Santos BS, et al. Clinical Oral Investigations. Effectiveness of desensitizing toothpastes in reducing tooth sensitivity after tooth bleaching: a systematic review. 2024. Accessed October 26, 2026.

Last reviewed by the Dental Health Time editorial team, against the sources above. How we review.

Toothpaste RDA ChartSearch and compare toothpaste abrasivity Teeth Stain Risk QuizStain risk score, prevention and whitening Tooth Sensitivity QuizSensitive teeth → likely causes and what helps How Long Dental Work LastsHow long crowns, fillings and implants last