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Convert carbamide peroxide to hydrogen peroxide
Whitening gels and strips list either carbamide peroxide or hydrogen peroxide, while the EU and UK rules count the hydrogen peroxide present or released. Enter the percentage on the label: the tool gives its hydrogen peroxide equivalent and the limit it falls under.
How much hydrogen peroxide is in 10% carbamide peroxide?
At most 3.6%. Carbamide peroxide breaks down on contact with water into urea and hydrogen peroxide: multiply its percentage by 0.36 to get the hydrogen peroxide it can release. For example, 16% carbamide peroxide yields at most 5.8% hydrogen peroxide, under the EU limit of 6%, and 22% yields 7.9%, above it.
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Carbamide peroxide vs hydrogen peroxide: what is the difference?
Carbamide peroxide combines urea and hydrogen peroxide; on contact with water it breaks down and releases that hydrogen peroxide, which is the whitening agent. Both appear on labels, but the same percentage does not mean the same thing: 10% carbamide peroxide corresponds to at most 3.6% hydrogen peroxide, according to the EU Scientific Committee on Consumer Products (SCCP), in a 2007 opinion.
Why the rules count hydrogen peroxide
In the European Union, Regulation 344/2013 sets its limits as hydrogen peroxide present in the product or released, for example by carbamide peroxide: up to 0.1% for products sold to the public, 0.1 to 6% for whitening products supplied only to dentists, and nothing above. In the UK, the General Dental Council applies the same limits. A gel labeled 16% carbamide peroxide therefore falls among the products reserved for dentists, and a 35% gel is over the cap.
Common concentrations, converted
| Carbamide peroxide | Hydrogen peroxide, at most | In the EU and the UK |
|---|---|---|
| 10% | 3.6% | Through a dentist |
| 15% | 5.4% | Through a dentist |
| 16% | 5.8% | Through a dentist |
| 20% | 7.2% | Not allowed |
| 22% | 7.9% | Not allowed |
| 35% | 12.6% | Not allowed |
| 44% | 15.8% | Not allowed |
What a percentage doesn’t tell you
A concentration tells you neither what result to expect nor how your teeth will tolerate it. It also assumes the label is right: when researchers in Hungary test-bought high-strength gels online, one of the five delivered contained no active ingredient, two were about 80% weaker than stated and two up to 9% stronger. Follow your product’s instructions; for your own teeth, that’s one for a dentist to look at.
Sources
- European Commission (GreenFacts summary of the SCCP opinion, 2007) — Tooth whiteners & oral hygiene products containing hydrogen peroxide: what is hydrogen peroxide and what is it used for?
- Règlement (UE) n° 344/2013 de la Commission du 4 avril 2013 modifiant les annexes II, III, V et VI du règlement (CE) n° 1223/2009 relatif aux produits cosmétiques — peroxyde d’hydrogène, annexe III, entrée 12 (EUR-Lex)
- General Dental Council — Tooth Whitening Position Statement (July 2016)
- Fittler et al. — Rampant online marketing of teeth whitening products: evaluation of online information, labelling accuracy and quantitative analysis of high peroxide content gels (Heliyon, 2023)
Keep reading
How to use whitening strips
The three EU levels, the pace of sessions and when to pause.
How to whiten teeth naturally
What the studies found on household peroxide, baking soda and other remedies.
How to make teeth whiter
Toothpaste, strips, LED kits, the dentist: what each method shows.
An Enamel team tool. The calculation follows the equivalence published by the EU scientific committee; it is not regulatory advice. Our editorial approach