Compare annual pregnancy risk and monthly probability for up to four contraceptive methods side by side, with typical-use and perfect-use failure rates.
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Usage scenario
Accounts for real-world inconsistency and human error.
Select up to 4 methods to compare
3/4 selected
No Contraception
None
85%
annual risk
Monthly risk: ~14.6%Effectiveness: 15.0%
Baseline risk for sexually active couples not using contraception.
Male Condom
Barrier
18%
annual risk
Monthly risk: ~1.6%Effectiveness: 82.0%
Also protects against STIs. Effectiveness drops with incorrect use or breakage.
Combined Pill (Oestrogen + Progestogen)
HormonalHormonalPrescription
9%
annual risk
Monthly risk: ~0.8%Effectiveness: 91.0%
Typical-use failure mostly due to missed pills. Must be taken daily.
Medical notice
Failure rates are population-level estimates from CDC and WHO data. Individual effectiveness
depends on consistent and correct use. Discuss contraceptive options with your GP or sexual
health clinician, especially if you have health conditions or take other medications.
Contraceptive effectiveness is measured as the percentage of women who do not experience an unintended pregnancy in the first year of use. Two key metrics are reported: typical-use failure rate (real-world use, including inconsistency and user error) and perfect-use failure rate (consistent, correct use every time). This calculator lets you compare up to four methods side by side.
Typical use vs perfect use
The gap between typical and perfect use is largest for user-dependent methods like condoms and the pill. For the combined oral contraceptive pill, perfect use yields a failure rate of ~0.3%, while typical use is ~9% — a 30-fold difference driven primarily by missed doses. Long-acting reversible contraceptives (LARCs) like the implant and IUDs have almost no difference between typical and perfect use because they require no ongoing action by the user.
When choosing a contraceptive method, consider how reliably you can follow the method's requirements. A theoretically effective method used inconsistently may perform worse than a less effective method used perfectly.
Emergency contraception
Emergency contraception (the morning-after pill or copper IUD) is not for regular use but can significantly reduce pregnancy risk after unprotected sex. The copper IUD, when fitted within 5 days of unprotected sex, is the most effective emergency contraceptive at over 99% effectiveness.
The emergency contraceptive pill is most effective within 24 hours but can be used up to 72–120 hours depending on the formulation. It does not protect against future acts of unprotected sex.
Frequently asked questions
Which contraceptive method is most effective?
The subdermal implant (e.g. Nexplanon) and hormonal IUS (e.g. Mirena) are the most effective reversible methods at over 99.8% effectiveness. Vasectomy and tubal ligation are the most effective overall. For those who cannot use hormones, the copper IUD offers over 99% effectiveness without any hormonal effect.
Do failure rates account for STI protection?
No — failure rates in this calculator refer only to pregnancy prevention. Male condoms are the only contraceptive method that also provides significant protection against sexually transmitted infections (STIs). For STI prevention, condoms should be used even when a hormonal or long-acting method is in place.
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