Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 6/23/2020
If you’re sexually active and don’t want to become pregnant, using a safe and reliable form of birth control is your best option for avoiding pregnancy.
There are numerous different forms of birth control available, from over-the-counter products such as condoms to prescription medications and devices such as the birth control pill, patch, ring, implant, IUD and more.
The different forms of birth control that are available vary hugely in effectiveness, with some almost perfect at preventing pregnancy and others significantly less effective.
Below, we’ve explained how birth control effectiveness works. We’ve also listed the most and least effective forms of birth control to help you make informed, effective decisions about your reproductive health and wellbeing.
Before we get into which form of birth control is most effective, it’s important to explain how the effectiveness rate of different forms of birth control is calculated.
If you’ve searched online for information about birth control effectiveness before, you may have seen different forms of birth control mentioned as being “99 percent” or “91 percent” effective at preventing pregnancy.
You may have also seen different percentages used to refer to a contraceptive’s effectiveness in “perfect” and “real life” scenarios.
In order to put these numbers into context, it’s important to understand how they work and what they mean.
The effectiveness of different forms of contraception is usually calculated using a system called the Pearl Index. The Pearl Index measures the number of contraceptive failures (pregnancies) that occur per 100 woman-years of contraceptive use.
In other words, a contraceptive’s Pearl Index measures how many women will become pregnant each year per 100 women using that type of contraceptive. The lower any form of birth control’s Pearl Index is, the more reliable and effective it is at preventing pregnancy.
For example, the hormonal intrauterine device (IUD) has a Pearl Index of 0.16. This means that fewer than one out of every 100 women who use the hormonal IUD will become pregnant during each year of use.
Expressed differently, 99.84 percent of sexually active women who use the hormonal IUD won’t become pregnant each year.
Using no contraception at all, on the other hand, has a much higher Pearl Index of eighty-five. In other words, only 15 percent of sexually active women of reproductive age who don’t use any form of contraception won’t become pregnant each year.
Most forms of contraception have two different Pearl Indexes. The first is the Pearl Index for the contraceptive when it’s used perfectly, while the second takes into account common errors that occur when contraceptives are used in a real-life, non-clinical environment.
These two Pearl Indexes can vary by quite a large amount, especially for forms of birth control that are easy to forget about or use improperly during sex.
For example, condoms have a very low Pearl Index of two when used perfectly, meaning that 98 percent of women won’t become pregnant for each year of perfect use.
However, because it’s relatively common to make mistakes when using a condom, the real life Pearl Index for condoms is 12 to fifteen. This means that only 85 percent to 88 percent of women who use condoms exclusively won’t become pregnant each year.
Depending on the specific resource you use to check birth control effectiveness, you might see the Pearl Index expressed in one of several different ways:
As a number. For example, a certain form of contraception might have a Pearl Index of 5.0 or 6.1, referring to the number of women per 100 that will become pregnant for each year of use.
As a percentage of women who will become pregnant each year. This is the same as above, but expressed as a percentage. For example, a certain form of birth control might result in 5.0 or 6.1 percent of women who use it becoming pregnant annually.
As a percentage of women who won’t become pregnant each year. For example, the above methods of birth control would be referred to as being 95.0 and 93.9 percent effective at preventing pregnancy.
To keep everything simple and consistent, we’ve used the third method for all of the birth control effectiveness rates listed below.
The Pearl Index isn’t perfect — over the years, researchers have highlighted several issues with the way it collects and uses data. It’s also an average based on study findings, meaning it may not translate directly into your exact real-world experience.
However, because of the Pearl Index’s age, simple calculation method and widespread use in studies of different forms of birth control, it’s become the most common method for calculating birth control effectiveness.
Other than abstaining from sex completely, the most effective forms of birth control are those that are good at preventing pregnancy, convenient and difficult to forget about or accidentally use improperly:
Intrauterine device (IUD). The intrauterine device, or IUD, is one of the most effective forms of birth control. The IUD is a tiny, T-shaped device that’s inserted into your uterus by a nurse or healthcare professional. Once inside, it prevents pregnancy for three to 12 years.
There are two different types of IUD that are currently available: the hormonal IUD and the non-hormonal IUD. Both are more than 99 percent effective at preventing pregnancy after they’re fitted by a nurse or healthcare professional.
Birth control implant. The birth control implant is a tiny, rod-shaped implant that’s fitted into your arm. Once inside, it releases hormones that prevent pregnancy. The implant is one of the most effective forms of birth control, with a 99 percent effectiveness rate.
Birth control shot (Depo-Provera®). The Depo-Provera birth control shot is 99 percent effective at preventing pregnancy when used perfectly. However, because some people forget to get their injection on time, it’s 94 percent effective in real-life conditions.
Birth control pill. The birth control pill is 99 percent effective at preventing pregnancy when it’s used perfectly. However, since it’s easy to forget about the pill, it’s 91 percent effective in real-life conditions.
Birth control patch. Similar to the birth control pill, the patch is 99 perfect effective at preventing pregnancy when it’s used perfectly. In real life, it’s easy to forget to change your patch on time, giving the patch a 91 percent real-life effectiveness rate.
Birth control ring. The NuvaRing® birth control ring is also 99 percent effective when used perfectly. Like other forms of hormonal birth control, the birth control ring is slightly less effective in real-life conditions, with a real life effectiveness rate of 91 percent.
Tubal ligation (or, for men vasectomy). Tubal ligation, or sterilization, is more than 99 percent effective at preventing pregnancy, meaning it’s the most effective form of birth control that’s currently available other than abstaining from sex.
However, it’s also a permanent method of birth control that you can’t reverse, meaning it’s only recommended if you’re sure that you don’t want to become pregnant. For men, getting a vasectomy has a similar effectiveness rate.
Other forms of birth control may not be as effective as the options listed above, either due to a low overall effectiveness rate or a higher risk of making mistakes. Less effective forms of birth control include:
Diaphragm. The diaphragm is a barrier-based method of birth control that prevents you from becoming pregnant by blocking your partner’s sperm from making its way through your cervix and coming into contact with an egg.
Used perfectly, the diaphragm is 94 percent effective at preventing pregnancy. However, in real life, its effectiveness rate is only 88 percent. It’s also worth noting that diaphragms work best when used in conjunction with spermicide.
Cervical cap. Another barrier-based method of birth control, the cervical cap works by covering your cervix and blocking your partner’s sperm. Its effectiveness varies based on how you use it, as well as whether or not you’ve had children.
For women who haven’t given birth, the cervical cap is 86 percent effective at preventing pregnancy. For women who have given birth, the cervical cap is only 71 percent effective at preventing pregnancy. And, as with the diaphragm, this efficacy is only achieved in conjunction with spermicde.
Birth control sponge. The birth control sponge, which covers your cervix and contains spermicide, varies in effectiveness depending on whether or not you’ve given birth.
For women who’ve never given birth, the sponge is 91 percent effective when it’s used perfectly and 88 percent effective in real-life conditions. For women who’ve given birth, the sponge is 80 percent effective if used perfectly and only 76 percent effective in real-life conditions.
Condoms. Condoms are effective when used correctly. However, since it’s quite easy to make mistakes when using condoms, their effectiveness rate is significantly lower in real life than it is under perfect use.
When they’re used perfectly, condoms are 98 percent effective at preventing pregnancy, while also providing protection from some STDs. In real-life conditions, condoms are 85 percent effective at preventing pregnancy.
Internal (female) condoms. When used perfectly, internal condoms are 95 percent effective at preventing pregnancy. They also provide protection from certain STDs. In real-life conditions, they’re approximately 79 percent effective at preventing pregnancy.
Spermicide. Spermicide is 82 percent effective at preventing pregnancy when it’s used perfectly and 72 percent effective when it’s used imperfectly. Spermicide is much more effective when used with other forms of birth control, such as condoms.
Withdrawal (pulling out). The withdrawal method is 96 percent effective at preventing pregnancy when it’s performed perfectly, meaning your partner withdraws before they ejaculate and makes sure no semen comes into contact with your vagina.
However, it’s easy to make mistakes using the withdrawal method. Because of this, it’s only 78 percent effective in real life.
Fertility awareness methods (FAMs). Fertility awareness methods (FAMs), such as the temperature, calendar and cervical mucus methods, vary from 76 to 88 percent effective at preventing pregnancy.
Many types of birth control can vary in effectiveness based on how you use them. For example, condoms are highly effective when used perfectly but become much less effective if you or your partner make a mistake while using them.
To make your birth control as effective as possible and reduce your risk of becoming pregnant, try using the following tips:
Most forms of birth control are relatively easy to use. However, it’s still important that you read the label that comes with your pills, patches or other contraceptives to check that you’re using them properly.
Seemingly small things such as the time of day you take your birth control pill or the exact day you change your patch can have a big impact on the effectiveness of your birth control.
The birth control pill quickly becomes less effective if you forget to take one or several doses in a row. If you often find yourself forgetting to take your pill, try setting a reminder on your phone or keeping your pill pack in a visible, obvious location that you won’t miss.
Condoms are very effective at preventing pregnancy, provided you and your partner have one on hand when the moment strikes. To avoid having to rely on your partner, it’s best to keep at least one condom in your bag so that you’re prepared in any situation.
Keeping a condom or two on hand not only reduces your risk of becoming pregnant — it’s also important for protecting yourself from sexually transmitted diseases (STDs).
Condoms work well when they’re put on your partner’s penis properly, but small mistakes can increase their risk of failure. For example, small things like allowing air to become trapped in a condom can increase its risk of breaking and exposing you to your partner’s semen.
To avoid making mistakes, it’s important to learn how to put on a condom properly. This guide from the CDC covers the right way to use a male condom and points out a few dos and don’ts that you’ll want to be aware of if condoms are your preferred form of birth control.
If you use a hormonal form of birth control such as the birth control pill, patch or ring, using a condom when you have sex will further reduce your risk of becoming pregnant and offer extra protection from STDs.
Population estimates suggest that using condoms with hormonal birth control may lower your risk of unplanned pregnancy by as much as 80 percent. It’s also okay to use condoms with non-hormonal forms of contraception, such as the sponge, diaphragm or copper IUD.
If your form of birth control fails, it’s important that you can access emergency contraception to reduce your risk of becoming pregnant.
Medications such as ulipristal acetate and the levonorgestrel morning-after pill, as well as options such as the copper IUD, can help you significantly lower your risk of pregnancy if used shortly after sex.
To avoid misunderstandings, it’s best to talk to your partner about birth control. Let them know what form of birth control you currently use and talk about how you’d like to make sure both of you stay safe from STDs or an unplanned pregnancy.
If you and your partner aren’t looking to have children, you may also want to talk about a permanent method of birth control such as tubal ligation or vasectomy.
Whatever you ultimately decide on, communicating openly with your partner about birth control can help you avoid misunderstandings and enjoy safer sex.
From condoms to the pill, the IUD and more, there are numerous different options available to reduce your risk of becoming pregnant if you’re sexually active.
Research shows that options such as the intrauterine device (IUD) and hormonal contraceptives such as the birth control implant, shot, pill, patch and ring tend to be most effective at preventing pregnancy when they’re used correctly.
On the other hand, barrier-based forms of birth control, such as condoms, offer protection from some STDs, meaning they may be worth considering. For optimal protection, you may choose to use both hormonal and barrier-based contraception.
There’s no ideal form of birth control for everyone. Choose a form of birth control that’s a good match for your needs, health and lifestyle to keep yourself and your partner protected from an unplanned pregnancy.
Working out which form of birth control to use can often be a confusing process. View our range of generic birth control pills online or read our complete guide to your birth control options to find out more about what’s available and which form of birth control is right for you.