Quick answer: Condoms are up to 98% effective at preventing pregnancy when used correctly every time, and 82% effective in typical use, according to the NHS. That 16-point gap is almost entirely down to how people use them, not to condoms breaking. The World Health Organization is blunt about it: very few pregnancies or infections happen because of slips or breaks.
Condoms are the only form of contraception that also protects against sexually transmitted infections, and they remain one of the most reliable options available when they're used properly. The catch is in that last phrase, and this guide is mostly about what it actually means.
Table of Contents
- What the 98% figure actually means
- What makes condoms effective
- Can everyone use condoms?
- Is it possible to get pregnant if you use a condom?
- Internal condoms and the 95% figure
- What actually causes condoms to fail
- Why lube changes the odds
- A note on spermicide
- Medicines and products that damage condoms
- Why you should never use two condoms
- What to do if a condom splits or comes off
- How well condoms protect against STIs
- Are latex condoms more effective than non-latex?
- How to tell a condom meets safety standards
- Where to get condoms in the UK
- Frequently asked questions
What the 98% figure actually means
Almost every article about condom effectiveness quotes 98%, and almost none of them explain that this number describes a scenario most people never achieve.
Contraception effectiveness is reported two ways. Perfect use describes what happens when the method is used exactly as intended, every single time, with no mistakes. Typical use describes what happens in real life, where people occasionally rush, occasionally skip, and occasionally get it slightly wrong.
For external condoms, the NHS puts perfect use at 98% and typical use at 82%, which works out at around 1 in 5 women who rely on condoms for a year becoming pregnant.
That gap is the entire story. Nothing about the condom itself changes between the two figures. The same product produces both numbers. What changes is whether it goes on before any contact, whether it stays on, and whether it gets used at all on the occasions when it should. Everything else in this guide is really about closing that gap.
What makes condoms effective
A condom works as a barrier. It sits between you and your partner and stops semen, and the skin-to-skin contact around the covered area, from crossing between you. That's the whole mechanism, and it's why condoms protect against both pregnancy and infection when nothing else does both.
The things that make the biggest practical difference are unglamorous:
- Putting the condom on before any genital contact, not partway through.
- Using a new one every time.
- Checking the expiry date before you use it.
- Using the right size so it doesn't slip or split.
- Adding lubricant, particularly for anal sex.
Putting a condom on properly takes seconds and doesn't have to interrupt anything. If you've never been shown, our guide on how to put on a condom walks through it step by step, and getting this right is the single highest-value thing on the list.
Size matters more than most people expect. A condom that's too tight is more likely to split, and one that's too loose is more likely to slip off, which is why our condom size guide is worth five minutes before you buy. You can browse the full condom range once you know what you're looking for.
Can everyone use condoms?
Most people can. The NHS advises against latex condoms in two specific situations: if you have a latex allergy, or if you're using antifungal medicine on or around the anus, vulva and vagina, or penis and testicles.
If either applies, the answer isn't to go without. Non-latex condoms made from polyisoprene or polyurethane give you the same barrier protection without the latex. The packet always states what the condom is made from.
If you've had a reaction and you're not sure whether latex was the cause, our guide to latex condom allergy symptoms covers what to look for and what to switch to.
Is it possible to get pregnant if you use a condom?
Yes. No contraceptive method is 100% effective, and condoms are no exception.
At 98% perfect use, roughly 2 in every 100 women relying on condoms for a year would become pregnant. At 82% typical use, that rises to around 1 in 5. Both figures come from the same NHS guidance, and the difference between them is behaviour rather than product quality.
The NHS is specific about what counts as incorrect use, and the two examples it gives are worth memorising: putting a condom on after the penis has already touched the vagina, and a condom splitting or coming off during sex. The first is far more common than the second.
If you want belt-and-braces protection against pregnancy, combining condoms with a second method such as the pill or an implant is more effective than either alone, and it keeps the STI protection that other methods don't provide.
Internal condoms and the 95% figure
Internal condoms, still often called female condoms, are worn inside the vagina rather than on the penis. They work on the same barrier principle and they're the option that doesn't depend on a partner's cooperation to use.
They're slightly less effective than external condoms. The NHS puts them at 95% with perfect use and 79% with typical use, which is around 1 in 5 women becoming pregnant over a year of typical use. The WHO quotes the same 95% figure.
The gap between 98% and 95% is real but small, and an internal condom used consistently will always beat an external condom used occasionally. If it suits you better, that's the one to use. condoms.uk carries internal condoms alongside the standard range.
One thing to know: don't use an internal and an external condom at the same time. The same friction problem that applies to doubling up on external condoms applies here.
What actually causes condoms to fail
This is where most articles on the subject get the emphasis wrong, including the earlier version of this one.
The instinctive worry is breakage. The WHO's position is that very few pregnancies or infections occur due to slips or breaks. The risk sits overwhelmingly with condoms not being used correctly, or not being used at all, on a given occasion.
The most common problems, in rough order of how often they cause trouble:
- The condom goes on after sex has already started, so there's been contact before any barrier existed.
- No condom is used at all that time, for whatever reason.
- The condom is removed before sex has finished.
- No space is left at the tip to collect semen, so pressure builds and the condom is more likely to split.
- The condom is put on inside out, turned over, and reused rather than replaced.
- The condom is expired or has been stored badly.
- The condom is damaged when the packet is opened, often by teeth or nails.
Reading that list, six of the seven are decisions rather than defects. That's genuinely good news, because it means the effectiveness of your own condom use is largely within your control.
On storage and expiry, heat and friction degrade condoms over time, which is why a wallet is one of the worst places to keep one. Our article on how long condoms last covers what to check and where to keep them.
Why lube changes the odds
The original version of this article didn't mention lubricant once, which was an omission, because it's one of the few things you can add that measurably reduces the chance of a condom failing.
The WHO states that lubricant makes it less likely a condom will break, slip or come off, and that it can improve the experience at the same time. That matters twice over, because a condom that feels better is a condom that's more likely to get used next time.
Two rules govern which lubricant to use:
Water-based or silicone-based only. These are safe with every condom material.
Never oil-based with latex. This is one of only two "don'ts" on the NHS condoms page. The WHO names kitchen oil, butter and hand lotion specifically as things that cause latex condoms to break. Massage oils, petroleum jelly and many body moisturisers fall into the same category.
Lubricant matters most for anal sex, because the rectum produces no natural lubrication, so a condom used without it is under far more friction. The WHO also flags lubricant as useful for anyone experiencing vaginal dryness, including around the menopause.
If you're unsure which type suits you, our comparison of water-based and silicone lube explains the trade-offs, and you can browse the lube range for something that pairs with your condoms.
A note on spermicide
An earlier version of this article suggested adding spermicide, or choosing a condom containing it, as a way to increase effectiveness. That advice was out of date and we've removed it.
Spermicides containing nonoxynol-9 do not protect against HIV and may increase the risk of infection in women who use them frequently, according to the WHO, which specifically advises women at high risk of HIV against using nonoxynol-9 spermicides for contraception.
A Cochrane systematic review reached the same conclusion, finding no evidence that nonoxynol-9 protects against HIV and evidence that it may cause harm by increasing genital lesions, with a statistically significant increase in that risk among women using it.
The practical takeaway is simple. A standard condom used correctly, with a water-based or silicone-based lubricant, is the better combination. You don't need spermicide to reach the 98% figure, and the barrier is what's doing the work.
Medicines and products that damage condoms
Beyond oil-based lubricants, some medicines applied to the genital area can degrade condom material.
The NHS advises against using latex condoms while you're using antifungal medicine on or around the genitals or anus. Creams, pessaries and suppositories for conditions such as thrush can weaken latex, polyisoprene and polyurethane, which means the condom may fail without any obvious warning.
If you're mid-treatment for thrush, use an additional or alternative method of contraception until the course is finished, and speak to a pharmacist if you're unsure how long to wait.
Why you should never use two condoms
Doubling up feels like it should double the protection. It does the opposite.
The NHS lists this as one of its two "don'ts": using more than one condom can make one or both split. Two layers of latex rubbing against each other generate friction that neither is designed to withstand, and the result is a higher chance of failure, not a lower one.
The same applies to wearing an internal condom and an external condom together. One condom, correctly sized and properly lubricated, is the safest configuration.
What to do if a condom splits or comes off
This is the moment that brings most people to an article like this one, and it's worth being direct about it.
The NHS treats a split or slipped condom as an urgent matter and advises getting help from a pharmacist, a sexual health clinic, 111 or a GP. You may need emergency contraception, an STI test, or both.
Timing matters for emergency contraception. The NHS guidance on emergency contraception sets out the options and the windows in which each one works, and the sooner you act the more options remain open to you. You can contact 111 online at any hour if you're not sure where to start.
STI testing works on a different timescale to emergency contraception, so a clinic will advise when to test rather than testing immediately. Don't let the wait put you off making the appointment.
Practical note for afterwards: check whether the condom was the right size, whether lubricant was used, and whether it was in date. A split usually has a cause, and identifying it stops the same thing happening again.
How well condoms protect against STIs
Condoms are the only contraceptive method that also reduces STI transmission, which is why the NHS describes using one every time as the best way to protect yourself and your partner from HIV and other STIs.
The scale of that effect is significant. A modelling study published in the National Library of Medicine's PubMed Central archive estimated that increased condom use since 1990 has averted around 117 million new HIV infections worldwide. The WHO also notes that most of the 374 million new curable STI infections recorded globally in 2020 could have been prevented by correct condom use.
Protection isn't uniform across every infection. Condoms are most effective against infections carried in bodily fluids, and less complete against infections that spread through skin contact beyond the area a condom covers. We've covered that distinction in detail in our guide to whether condoms protect against STIs, which is the better place to look if that's your main question.
Are latex condoms more effective than non-latex?
No. Both provide the same barrier protection when used correctly, and the effectiveness figures quoted throughout this article apply to both.
Latex comes from rubber trees and is the most widely used condom material. Polyisoprene is a synthetic version of the same polymer, made without the natural proteins that trigger latex allergies, and many people find it feels closer to latex than the alternatives. Polyurethane is a different plastic altogether, thinner and better at conducting heat, and compatible with oil-based lubricants where latex isn't.
The choice between them is about allergies and preference rather than protection. Someone with a latex allergy is far better served by a non-latex condom they can use comfortably than by a latex one they'll avoid.
One material is a genuine exception. Lambskin condoms, made from animal intestine, prevent pregnancy but do not reliably protect against STIs, because the material contains pores small enough to block sperm but not viruses. If STI protection matters to you, and for most people it should, lambskin isn't a suitable choice. condoms.uk doesn't stock it.
How to tell a condom meets safety standards
Check the packet for a CE mark or a UKCA mark. The NHS advises looking for a European CE mark or UKCA mark, which means the condom has been tested to high safety standards. UKCA stands for UK Conformity Assessed and is the British marking introduced after Brexit. CE is the European equivalent, and both remain valid in the UK.
The WHO adds that condoms should meet ISO standards and WHO/UNFPA specifications to ensure their effectiveness. Any condom sold by a reputable UK retailer will meet these, but it's worth a glance at the box if you've bought from an unfamiliar source or picked something up abroad.
Also check the expiry date. An expired condom may not perform as intended, and it's the easiest thing on this list to verify.
Where to get condoms in the UK
Contraception is free and confidential on the NHS. You can get condoms free from sexual health clinics, some GP surgeries and pharmacies, and some young people's services. The NHS has a service finder for contraception services if you'd like to use one.
This applies to under-16s too. The NHS is clear that contraception is free and confidential regardless of age, and that a doctor, nurse or pharmacist won't tell anyone, including parents or carers, unless they believe someone is at risk of harm.
Buying online gives you a wider choice of sizes, materials and styles than most free schemes carry, which matters if fit has been a problem for you. You can browse the full condom range at condoms.uk, delivered in discreet packaging.
The bottom line
Condoms are 98% effective with perfect use and 82% in practice, and the distance between those numbers is made up almost entirely of human decisions rather than product failures.
Put it on before any contact. Use a new one every time. Check the date. Get the size right. Add water-based or silicone-based lubricant, especially for anal sex. Skip the spermicide. Never use two at once. Do those seven things consistently and your own effectiveness rate sits much closer to the top of that range than the bottom.
And if something does go wrong, act quickly rather than waiting to see. Emergency contraception is time-sensitive, and a clinic would far rather see you the next morning than a month later.
Frequently asked questions
How effective are condoms at preventing pregnancy?
Condoms are up to 98% effective at preventing pregnancy when used correctly every time you have sex, and 82% effective with typical use, according to the NHS. Typical use accounts for the ordinary mistakes people make, such as putting a condom on partway through sex or not using one on a particular occasion. The 16-point difference between those figures reflects behaviour rather than any difference in the condoms themselves.
Why are condoms not 100% effective?
No contraceptive method is 100% effective. For condoms, the shortfall is mostly down to how they're used rather than the product failing. The most common problems are putting the condom on after genital contact has already happened, removing it before sex has finished, leaving no space at the tip, or not using one at all on a given occasion. The WHO states that very few pregnancies or infections result from condoms slipping or breaking.
What does typical use mean?
Typical use is the effectiveness rate measured across real-world users, including everyone who occasionally uses the method incorrectly or inconsistently. Perfect use describes the rate among people who use the method exactly as instructed every single time. Both figures are quoted for every contraceptive method, and the gap between them is usually the most informative thing about how a method performs in practice.
Are internal condoms as effective as external ones?
Not quite. The NHS puts internal condoms at 95% effective with perfect use and 79% with typical use, compared with 98% and 82% for external condoms. The difference is real but modest, and an internal condom used consistently offers better protection than an external condom used only sometimes. Choose whichever you'll actually use every time.
Does lube make condoms more or less effective?
Water-based and silicone-based lubricants make condoms more effective, because the WHO notes they reduce the chance of a condom breaking, slipping or coming off. Oil-based lubricants do the opposite with latex condoms and can cause them to break. That includes kitchen oil, butter, hand lotion, massage oil and petroleum jelly. Stick to water-based or silicone-based products with latex.
Should I use condoms with spermicide?
Current guidance says no. The WHO advises that spermicides containing nonoxynol-9 do not protect against HIV and may increase infection risk in women who use them frequently, and a Cochrane review found evidence of harm through increased genital lesions. A standard condom used correctly with a water-based or silicone-based lubricant is the better combination, and the barrier itself is what delivers the protection.
Can I use two condoms for extra protection?
No. The NHS specifically advises against using more than one condom, because friction between the two layers can cause one or both to split. The same applies to combining an internal condom with an external one. A single, correctly sized, properly lubricated condom is the safest option.
What should I do if a condom splits?
Treat it as urgent. The NHS advises getting help from a pharmacist, a sexual health clinic, 111 or a GP, and you may need emergency contraception, an STI test, or both. Emergency contraception is time-sensitive, so the sooner you act the more options are available. STI testing works to a different timescale and a clinic will advise when to test.
Do condoms protect against all STIs?
They significantly reduce the risk of most STIs but not equally across all of them. Condoms are most effective against infections transmitted through bodily fluids, and less complete against infections that spread via skin contact outside the area the condom covers. The NHS still describes consistent condom use as the best way to protect against HIV and other STIs.
Does condom size affect how well they work?
Yes. A condom that's too tight is more likely to split under tension, and one that's too loose is more likely to slip off during sex. Both outcomes reduce effectiveness. Nominal width is the measurement that matters most, and getting it right is one of the simplest ways to improve how reliably condoms work for you.
Can medicines stop condoms working?
Some can. The NHS advises against using latex condoms while you're using antifungal medicine on or around the anus, vulva and vagina, or penis and testicles. Creams, pessaries and suppositories for conditions such as thrush can weaken latex, polyisoprene and polyurethane. Use an additional or alternative method until the treatment course is finished.
Do expired condoms still work?
Not reliably. The NHS advises checking the use-by date before use, because an expired condom may not be effective. The material degrades over time, and heat and friction accelerate that, which is why storing condoms in a wallet or a car is a poor idea. If the packet is damaged, brittle or past its date, use a different one.
Are lambskin condoms as effective as latex?
For pregnancy prevention they work, but for STI protection they don't. Lambskin is made from animal intestine and contains pores that are small enough to block sperm but large enough to allow viruses through. If STI protection is a consideration, and for most people it should be, choose latex, polyisoprene or polyurethane instead.
This article is for informational purposes only and does not constitute medical advice. If you are concerned about pregnancy, a possible STI exposure, or a reaction to a condom or lubricant, speak to a pharmacist, your GP or a sexual health clinic, or visit NHS.uk. If a condom has split or come off, seek advice promptly, as emergency contraception is more effective the sooner it is taken.
