Know your cycle better in less than an hour.
Nineteen short lessons give you a clear, practical introduction to the Billings Method. What to notice, what your observations mean, and how your cycle’s patterns begin to tell a story.
No account, no card, no catch.
19 short lessons in 5 modules
Self-paced and completely free
Finish all 19 and earn your Corvia Certificate of Completion
The method Corvia is built on
A scientifically grounded way to understand your cycle by paying attention to what your body is doing today. Not predicting what it should do based on a calendar.
No temperature taking. No internal exams. No wearable required. Just one daily observation of the sensations and signs your body naturally produces.
Your body is already talking. Billings teaches you how to listen.
Not the rhythm method
The Rhythm Method and the Billings Method are often confused. They work very differently.
Rhythm Method
Guesses when you are fertile based on the length of past cycles. It assumes your body will follow a calendar.
Based on averages. Not you.Billings Method
Reads what your body is doing right now through the sensation at the vulva and the appearance of any discharge. Your cycle tells you where you are. No guessing.
Based on your body. Always.That means a long cycle, short cycle, delayed ovulation, stressful month, postpartum season, or changing pattern doesn’t have to fit a predetermined calendar. You observe what is actually happening today.
The core principle
As ovulation approaches, rising estrogen changes the mucus produced by the cervix.
Those changes can be noticed externally at the vulva, often as a progression from a familiar baseline toward sensations that feel increasingly wet or slippery.
Near ovulation, the sensation becomes distinctly slippery. After ovulation, progesterone rises and that slippery sensation ends.
That shift is the foundation of the Billings Method.
You don’t predict ovulation. You observe the hormonal changes happening around it. No internal examination is required. Sensation is noticed naturally throughout the day during ordinary activities.
What women observe
Once a day, at the end of the day, you record what you noticed at the vulva.
What you felt matters more than what you saw.
The important part isn’t memorizing the words. It’s learning your pattern and recognizing when that pattern changes.
These are the eight options Corvia’s daily check-in offers, in this order.
Your baseline
During the early infertile phase of a cycle, most women experience a stable, unchanging pattern. Billings calls this the Basic Infertile Pattern, or BIP.
For some women, the BIP is dryness. Nothing felt, nothing seen, day after day. For others, it may include a small amount of discharge that remains essentially the same from one day to the next. The specific observation is less important than its consistency.
Fertility announces itself through change. When something becomes different, a different sensation, a different appearance, a different pattern, you stop assuming infertility and begin paying closer attention.
Know your normal. Notice the change.
In Corvia
You tell Corvia which baseline is yours when you set up your profile: a dry baseline, an unchanging-discharge baseline, or still learning. That choice changes how your moist, damp and wet days are read, because an unchanging discharge is a baseline for one woman and a change for another. You can update it any time in your profile.
Peak Day
As fertility develops, the sensation at the vulva may become increasingly wet and eventually slippery. The last day of slippery sensation is called Peak Day. Peak is closely associated with ovulation and represents the time of greatest fertility.
But there’s a catch. You cannot confirm Peak until the next day. You know a day was Peak because the slippery sensation is gone. The change may be to dry, sticky, or another sensation, but it is no longer slippery.
That is why Billings is not about predicting what happens next. You observe. Then you interpret the pattern your body actually gave you.
The shape of a cycle
The number of days may change. The timing of ovulation may change. But once you understand the pattern, the cycle begins to have a recognizable shape.
01
Menstruation
Bleeding begins a new cycle. Observation continues, although heavy bleeding can mask other signs.
02
Basic Infertile Pattern
A stable pattern begins to emerge. For many women this is dryness. For others it may be an unchanging discharge.
03
Developing pattern
Something changes. The sensation or appearance becomes different from the established Basic Infertile Pattern and develops over time.
04
Peak
The final day of slippery sensation. Ovulation occurs close to this time.
05
Three days after Peak
Although the slippery sensation has ended, the method continues to treat these three days as potentially fertile. Corvia marks them X1, X2 and X3.
06
Post-ovulatory infertility
From the fourth day after Peak, the post-ovulatory infertile phase begins and continues until menstruation.
Then a new cycle starts, and you observe again. One day at a time. One pattern at a time.
Using what you observe
The Billings Method has four rules for couples using the method to postpone pregnancy. The same observations also help couples identify the most fertile part of the cycle when they hope to conceive.
Early Day Rule 1
Avoid intercourse on days of heavy menstrual bleeding.
In a short cycle, fertility may begin before bleeding has ended. Heavy bleeding can hide the mucus signs that would otherwise indicate fertility.
Early Day Rule 2
During an established Basic Infertile Pattern, intercourse is available on alternate evenings.
Waiting until evening gives a woman the day to confirm that her usual pattern has not changed. Alternating evenings also allows an intervening day of observation, since seminal fluid following intercourse can make interpretation more difficult.
Early Day Rule 3
When the Basic Infertile Pattern changes: wait and see.
A change may be the beginning of fertility, even if ovulation does not happen immediately. The developing pattern is observed until Peak can be identified or the Basic Infertile Pattern returns.
The Peak Rule
Once Peak is identified, count three full days.
For couples postponing pregnancy, intercourse is avoided through the third day after Peak. From the beginning of the fourth day past Peak until menstruation, the cycle is considered infertile.
Trying to conceive?
What changes is how you use the information. The slippery sensation identifies the time of highest fertility, helping a couple recognize the days when intercourse is most likely to result in conception.
Same body. Same method. Different intention.
Faith & fertility
Catholic teaching recognizes that married couples may have serious reasons to postpone a pregnancy. The question isn’t whether couples may discern the timing of another child. It’s how they do it.
The Church supports methods of family planning based on self-observation and the use of naturally infertile periods because they work with fertility rather than suppressing or altering it. Billings is one way couples can live that out.
01
Works with the body
Fertility is observed, not suppressed.
02
Respects the marital act
The act itself is not altered.
03
Invites discernment
Couples prayerfully respond to what the woman observes.
04
Shared by spouses
Fertility becomes a conversation, not a burden.
Nothing is added. Nothing is suppressed.
Fertility isn’t treated like something broken that needs to be switched off. The couple learns how the woman’s body works and respects what it is doing. When a couple prayerfully discerns that pregnancy should be postponed, they abstain during fertile days rather than changing the marital act itself.
Fertility becomes something shared.
The woman may make the daily observation, but the discernment belongs to both spouses. NFP asks couples to communicate about fertility, intentions, sacrifice, parenthood, and the life they are building together.
Responsible parenthood includes discernment.
Catholic teaching isn’t simply “have as many children as physically possible.” It calls spouses to generously welcome life while prayerfully considering their responsibilities to God, one another, their existing children, and the circumstances of their family.
Faith and fertility were never meant to be separate.
The Catholic Church does not require the Billings Method specifically. Billings is one form of natural family planning consistent with the Church’s teaching on self-observation and the use of naturally infertile periods.
A seventy-year story
The Billings Method began with Australian physicians Drs. John and Evelyn Billings, whose clinical work with women began in the 1950s.
Over decades, they studied the patterns women observed at the vulva and worked alongside reproductive scientists, including Professor James B. Brown, to understand the hormonal events behind those observations.
The result was remarkably simple: changes a woman can recognize externally correspond with changes occurring internally throughout her reproductive cycle.
The method has since been taught across cultures, languages, reproductive stages, and cycle types around the world.
The technology is the woman’s own observation.
Effectiveness
Billings has been studied both as a method for postponing pregnancy and as a way to identify the fertile time when trying to conceive.
When the method is properly taught and its rules are correctly followed, published studies have found very low pregnancy rates among couples seeking to avoid pregnancy. Research has also found that identifying the fertile pattern can help couples time intercourse when seeking pregnancy, including couples who have previously experienced difficulty conceiving.
But numbers only tell part of the story. Method effectiveness depends on knowing the method. Billings is not simply “look for mucus.” It depends on establishing an individual Basic Infertile Pattern, recognizing change, correctly identifying Peak, and applying the rules consistently.
That’s why women using Billings for family planning are encouraged to learn with an accredited instructor.
The method is simple. Learning your own pattern is personal.
View the research →More than fertility
Charting isn’t only about answering “am I fertile today?” Month after month, your observations begin to create a picture of how your body typically behaves. You may start noticing:
A chart cannot diagnose a medical condition. But it can give you something incredibly useful: a detailed record of what changed and when.
That record can be shared with your Billings instructor or healthcare professional when something doesn’t look like your normal.
Learn it the right way
Billings 101 gives you the foundation: the observations, the patterns, Peak, the rules, and the science underneath them. It’s a great place to begin.
But if you plan to rely on Billings to avoid or achieve pregnancy, there is no substitute for learning your individual pattern with an accredited Billings instructor. A trained instructor can look at your actual chart, answer questions, and help you interpret situations that a general course simply can’t anticipate.
Billings 101 teaches the method. An instructor helps you learn your body.
Your Corvia Billings 101 Certificate of Completion recognizes completion of Corvia’s educational course. It is not certification or accreditation as a Billings Ovulation Method instructor.
Where Corvia fits
The Billings Method teaches you how to understand what your body is telling you. Corvia gives you a beautiful place to live that practice every day.
And bring the fertility conversation into the same place you bring everything else that matters: your prayer life.
Corvia doesn’t replace the method. It was built around it.
The marks you’ll see on your chart
Billings records each day as a stamp. This is the same legend that sits at the top of your chart in Corvia, so the vocabulary on this page is the vocabulary you’ll meet on day one.