The two figures, and which one is yours
Condom effectiveness is published as two numbers because it is measured two ways: typical use and perfect use (Wikipedia). The typical-use figure is 87%, and the perfect-use figure is 98%. If you want the single most useful sentence: 87% describes how condoms perform for people having sex the way people actually do, and 98% describes how they perform when every use is correct and consistent.
So the figure that describes your own use is 87% unless you can honestly say every single act of intercourse involves a correctly applied condom from start to finish, with no slip, no break, and no skipped occasion. Most people cannot say that, which is why the typical-use number is the one to plan around. The 98% figure is not a marketing number — it is the ceiling that correct, consistent use reaches.
What typical use actually includes
Typical use is not a euphemism for carelessness. It is the measured performance of condoms across real-world use, and the gap between 87% and 98% comes from the things that go wrong in practice: condoms that split or slip off, and occasions when a condom is not used at all (Brook). Those three failure routes — slip, break, and non-use — are what the 87% figure is built to absorb.
That matters for how you read the number. A split condom is not a moral failure; it is one of the events the typical-use statistic already accounts for. Brook notes that if a condom splits or slips off, or you are worried, you may need emergency contraception (Brook). The practical takeaway is that the 87% figure assumes some of this will happen. It is the honest baseline for a sexually active person rather than a worst case.
What perfect use requires
Perfect use is a narrow, specific standard, and it is worth knowing exactly what it asks so you can judge how close you are. It requires three conditions held together: a condom used correctly, used consistently, and used every time. Correct use means the condom is applied properly and remains intact. Consistent use means it is used for the whole of every act, not partway. And every-time use means no exceptions (Wikipedia).
When all three hold, the published figure is 98%. When any one of them lapses. A condom put on late, a break, a night without one. You are no longer in the perfect-use group, and the 87% figure is the one that applies. This is why the two numbers are not in competition: they describe two different populations of use, and the only question is which population your behaviour puts you in.
Placing yourself on the scale
To place yourself, ask three questions in order. Do you use a condom every time you have intercourse? Do you use it for the entire act, from start to finish? And have you had a slip or break in the recent past? If the answer to all three is a clean yes, the 98% figure describes your use. If any answer is no or uncertain, the 87% figure is the one to plan around (Wikipedia).
There is no partial credit between the two numbers, and that is the point of the scale. A person who is usually careful but occasionally skips a condom is in the typical-use group, not somewhere in the high nineties. Being honest about which group you are in is what makes the number useful, because it tells you whether the gap between 87% and 98% is something you have already closed or something you could still close.
Closing the gap
Closing the gap means moving your own behaviour toward the perfect-use conditions, and the evidence points to concrete steps rather than general caution. Use a new condom each time you have sex (Brook). Use only water-based or silicone lubricant with latex condoms, because oil-based products can damage latex (Planned Parenthood). And if a condom splits or slips, treat it as a real event and seek emergency contraception advice rather than waiting (Brook).
- Use a new condom every time you have sex (Brook).
- Use only water-based or silicone lubricant with latex condoms — oil-based products can damage latex (Planned Parenthood).
- If a condom splits or slips off, or you are worried, seek emergency contraception advice (Brook).
- If you have a latex allergy, choose a condom made from a material other than latex, such as polyurethane (Wikipedia).
Those four steps are the practical route from the 87% group toward the 98% group. None of them requires special equipment, and each one removes a specific failure route rather than adding a general instruction to be more careful.
What the figure does not cover
The 87% and 98% figures are about pregnancy prevention, and they should not be read as a complete statement of protection. Condoms also protect against sexually transmitted infections by preventing sexual fluids from being transferred between partners (Brook), and latex condoms in particular help protect against both pregnancy and STDs (Planned Parenthood). STI protection is a separate benefit from the pregnancy figure, and it depends on the condom being used, not on the percentage.
That separation matters when you are deciding what to do next. If your concern is pregnancy, the 87% and 98% figures are the right frame. If your concern is STI risk, the relevant fact is that condoms reduce transmission by preventing fluid exchange, and the CDC’s guidance is to know how to protect yourself and your sex partner or partners from STIs (CDC). If you have had unprotected sex and are concerned about STIs, testing is the route to certainty, and STIs can take up to 7 weeks after unprotected sex to show up on a test (NHS).
The stop boundary
The two figures answer the pregnancy question and nothing more. Once you know whether you are in the 87% group or the 98% group, the remaining decisions. STI testing, emergency contraception after a break, or a change of method. Are separate questions with their own routes, and the sources above are the places to take them.