Best time to get pregnant calculator

When is the best time to conceive? Enter the first day of your last period and your usual cycle length. You will see your fertile window, your best days to try and when to expect your next period.

Your cycle

First day of your last period

Average cycle length Count from day 1 of one period to day 1 of the next. 28 days is a common starting point.

Adjust days between ovulation and your next period

Luteal phase length 14 days suits most people. Change it only if you have tracked a different pattern.

Dates stay in your browser. We never receive them.

Example: a 28-day cycle

Pick a date to see your own best days

This is how a typical cycle looks. Your dates replace it as soon as you enter the first day of your last period.

First day of period
Fertile window
Best days
Ovulation

OvulationDay 15About 14 days before the next period starts.
Fertile windowDays 10 to 15Five days before ovulation, plus ovulation day.
Best daysDays 13 to 15The two days before ovulation and ovulation day.

Your best days to try

Estimated ovulation

Fertile window

Next period

Due date if you conceive this cycle

First day of period
Fertile window
Best days
Ovulation

Your next three cycles

Cycle starts	Fertile window	Ovulation	Next period

More pregnancy calculators

See all pregnancy calculators

How the best days are worked out

1Find your ovulation day Next period minus 14 days Ovulation tends to happen about 14 days before your next period starts. A longer cycle moves ovulation later, and a shorter one moves it earlier.
2Open the fertile window Ovulation minus 5 days Sperm can wait in the reproductive tract for up to about five days, and an egg lasts roughly a day. That makes six fertile days: the five before ovulation and ovulation day.
3Pick your best days The last 3 fertile days The chance of pregnancy is highest in the two days before ovulation and on ovulation day. These are the days worth planning around.

What these dates can and cannot tell you

A calendar gives you a sensible starting point. It cannot see inside your body, so every date here is an estimate, and ovulation can happen earlier or later.

What the calculator uses

The first day of your last period.
Your average cycle length.
A luteal phase of 14 days, which you can change from 10 to 16 days if you have tracked a different pattern.

What it cannot tell you

Whether you ovulated this cycle, or on which day.
Whether tubes, sperm, fertilization and implantation are all working well.
Whether you are pregnant. A test does that, and a scan confirms the dates.
Whether it is safe to skip contraception. A fertile window estimate is not birth control.
How closely it matches ovulation that has been measured. It uses a standard formula and has not been checked against measured ovulation.

Ovulation often happens about 14 days before your next period. Cycle length and timing vary from person to person and from month to month, which is why a range works better than a single day.

Which tracking method fits you?

A calendar is the starting point. Add one more clue when you want more precision, and pick the one you can keep up without stress.

Method	What it can add	Keep in mind
Calendar or app (this calculator)	An estimated window based on your period dates.	Dates alone cannot confirm ovulation, and variability reduces precision.
Urine ovulation (LH) test	Detects the hormone surge that comes before ovulation.	A surge is indirect evidence, and false results and hard-to-read lines can happen.
Cervical mucus	Clear, stretchy mucus can mark potentially fertile days.	Reading it is subjective, and it does not show that conception will happen.
Basal body temperature	A temperature pattern helps you recognise ovulation after it has happened.	It is less useful for predicting the window in the same cycle.

A 2023 Cochrane review of seven randomised trials, with 2,464 women or couples, found that urine ovulation tests probably improved pregnancy and live-birth rates for women under 40 who had been trying for less than 12 months. Evidence for the other methods was less certain, and several trials were funded by manufacturers. Tests are an option and never a requirement.

Our guides cover the signs of ovulation and how to chart your temperature. A temperature chart confirms ovulation after it happens, which helps you learn your own pattern over a few months.

When to have sex to get pregnant

Have sex in the six days that end on ovulation, and the days closest to ovulation matter most. Pregnancy through vaginal sex is very unlikely outside that window, and the chance is highest in the two days before ovulation. You do not need to hit one exact day, because sperm can wait for the egg.

Sex on	Chance of pregnancy	Why
Before the window opens	Unlikely	Early ovulation can happen, especially in a short cycle.
Five to three days before ovulation	Possible	Sperm can wait in the reproductive tract for about five days.
The two days before ovulation, and ovulation day	Highest	The most useful days to plan around.
After ovulation day	Drops quickly	An egg can be fertilized for only about 12 to 24 hours after it is released.

The American Society for Reproductive Medicine notes that sex every one to two days in the window gives the highest pregnancy rates, and two to three times a week across the cycle gives nearly the same result. In the 28-day cycle shown above, the window runs from day 10 to day 15, so sex on days 10, 12, 14 and 15 covers a one-to-two-day rhythm. Your own dates appear as soon as you enter your last period.

If counting days feels like a chore, sex every two to three days across the whole cycle covers the window without any tracking. There is no need to hold back, and no position, or lying down afterwards, has been shown to improve the chance of pregnancy. Intimacy does not have to follow the calendar. Tracking and timed sex can become a burden, so simplify your routine, pause the reminders or take a month off whenever you need to. Difficulty conceiving is never a personal failure.

When a cycle runs long or short, the dates above move with it. Re-enter the first day of each new period to keep the estimate fresh. If your cycles vary by more than a week, have sex every two to three days, lean on ovulation tests and talk to your provider about why.

Cycle-based tools are less useful when ovulation is infrequent or unpredictable, as it can be with polycystic ovary syndrome (PCOS). Treatment for ovulation problems is a clinician's decision. An international PCOS guideline names letrozole as the first-line medicine for inducing ovulation when no other fertility factor is present, and it is not a self-treatment.

After you stop hormonal birth control, your first cycles may be irregular, and the contraceptive injection can delay a return to usual fertility for up to a year, according to the NHS. Our guide to coming off birth control explains what to expect.

Pregnancy tests are most reliable from the first day of a missed period, and our guide to when to take a pregnancy test explains how to get a clear result. When you have a positive result, the due date calculator turns your dates into a due date and a full list of milestones.

Your chances of getting pregnant each cycle, and when to ask for help

People often look for a chances of getting pregnant calculator, a pregnancy odds calculator or a pregnancy probability calculator. No tool can know your own fertility, because it depends on age, health, timing and some luck. A calculator can show which days carry the highest chance, which is what the dates above do, and the group figures below show how chances change with age.

Among healthy couples, about one in four become pregnant in a given cycle in their 20s and early 30s, and about one in ten at age 40, according to ACOG estimates. In the PRESTO study of 2,962 couples in the United States and Canada, 79.3% of people aged 25 to 27 and 55.5% of those aged 40 to 45 had become pregnant by 12 cycles. These are group figures that describe pregnancy rather than live birth, and they are not a forecast for you. A few cycles without a pregnancy is common, even with well-timed sex.

Situation	Usual time to seek an assessment
Under 35, no known concerns	After 12 months of regular unprotected sex without pregnancy
Age 35 to 40	After 6 months
Over 40	Sooner, because more immediate evaluation may be appropriate
Irregular or absent periods, suspected endometriosis or tubal disease, known sperm problems, sexual dysfunction or cancer treatment	Seek advice earlier, instead of waiting for the usual threshold

These thresholds come from US professional guidance. Both partners are assessed together, including a semen analysis where appropriate. The route into care differs by country, and some health systems ask for a referral from a family doctor first. The World Health Organization's first global infertility guideline (2025) emphasises fair access and adapting care to national circumstances, since not everyone can reach a specialist. Our guides on how long conception takes and trying after 35 go further, including how to find fertility care where you live.

Before you start trying

Start folic acid. Most national advice is 400 micrograms a day from before conception, and the end date differs by country. The folic acid guide compares them.
Book a preconception visit. Review long-term conditions, medicines (including over-the-counter and herbal products), vaccines and family history. Do not stop a prescribed medicine without advice.
Include the person providing sperm. A semen analysis is part of a standard assessment, and our male fertility guide explains it.
Keep food and supplements simple. No universal fertility supplement stack has been shown to help, and a varied, nutritious diet is a good base. See the best foods guide.

Common questions

Quick answers about timing, tracking and what to do when plans take longer.

When is the best time to get pregnant?

The best time is the two days before ovulation and the day of ovulation. Ovulation usually falls about 14 days before your next period starts, so the exact dates depend on your cycle length.

What is the best day to have sex to get pregnant?

The two days before ovulation and ovulation day itself. In a 28-day cycle with a 14-day luteal phase, ovulation falls on day 15 and the best days are days 13 to 15. Enter your last period above to see your own dates.

When should we start having sex in the cycle?

Start when your fertile window opens, which is five days before ovulation. In a 28-day cycle that is about day 10. If your cycle length varies, start a few days earlier, or have sex every two to three days across the whole cycle.

What are my chances of getting pregnant each month?

Among healthy couples about one in four become pregnant in a given cycle in their 20s and early 30s, and about one in ten at age 40, according to ACOG estimates. Your own chance depends on age, health, timing and some luck, and sex in the fertile window gives the best odds.

Is there a pregnancy probability or odds calculator?

No calculator can work out your personal probability, because it depends on fertility factors that dates cannot show. This page shows which days of your cycle have the highest chance, and the figures on this page show how chances change with age.

When is the best time to get pregnant after a period?

It depends on your cycle length. In a 28-day cycle, ovulation falls around day 15 and the best days are days 13 to 15, about two weeks after your period starts. In a shorter cycle the window opens earlier, so enter your own dates above.

How often should we have sex during the fertile window?

Every one to two days in the fertile window gives the highest pregnancy rates, and two to three times a week across the cycle gives nearly the same result without any tracking.

Should we have sex every day to get pregnant?

You can. There is no need to restrict how often you have sex, and daily sex in the window is fine. Because every other day works nearly as well, choose the rhythm that feels easy to keep up.

Do we need to time sex at all?

No. Sex two to three times a week across the cycle gives nearly the same pregnancy rates as timing sex to the fertile window, so timing is optional. A calendar and ovulation tests are there for people who want to plan.

Is it too late to have sex after ovulation?

The chance drops quickly after ovulation, because an egg can be fertilized for only about 12 to 24 hours after it is released. Ovulation tests and cervical mucus can help you see where you are in the cycle.

Does lying down after sex, or a certain position, help?

No. Specific positions and lying down afterwards have not been shown to improve the chance of pregnancy, and there is no need to limit how often you have sex.

How many days before ovulation can you get pregnant?

Up to five days. Sperm can survive in the reproductive tract for about five days, which is why the fertile window is six days long and ends on ovulation day.

Can I get pregnant right after my period?

It is unlikely and still possible. In a short cycle ovulation can come soon after a period ends, and sperm can live for several days.

How accurate is a calendar based fertile window?

It gives a starting estimate, and it cannot confirm that ovulation happened. Ovulation can shift from one cycle to the next, so ovulation tests, cervical mucus or a temperature chart can sharpen the dates.

What if my cycle is irregular?

A calendar estimate is less reliable when cycles vary a lot. Ovulation tests can help you spot the hormone surge, and a provider can look into why your cycle changes.

Do ovulation tests work?

A 2023 Cochrane review of seven trials found that urine ovulation tests probably improve pregnancy and live-birth rates for women under 40 who have been trying for less than 12 months. A surge is indirect evidence that ovulation is near, results can be hard to read and several trials were funded by manufacturers. Tests are an option, not a requirement.

Can I use the fertile window to avoid pregnancy?

No. Ovulation can move, so these dates cannot rule out pregnancy. A fertile window estimate is not a contraceptive method.

Can I use this after stopping birth control?

Yes, with care. Your first cycles may be irregular, so enter each new period as it starts and add ovulation tests. The contraceptive injection can delay a return to usual fertility for up to a year.

When should I take a pregnancy test?

Most home tests are most reliable from the first day of a missed period. If you do not know when your period is due, the NHS advises testing at least 21 days after the last unprotected sex. An early negative result may need repeating after a few days.

How long should we try before asking for help?

Assessment is usually suggested after 12 months of regular unprotected sex if you are under 35, after 6 months at 35 to 40, and sooner over 40 or with known concerns such as irregular periods. Routes into care and funding differ by country.

Is the fertile window the same in every country?

The biology is the same everywhere. Health bodies in Germany, the UK and the US teach the same core idea: sex in the days before ovulation and on ovulation day gives the best chance. What differs is how you reach tests and treatment, so check your own health system.