The short version. The fertile window is about six days each cycle: the five days before ovulation plus the day of. Having sex every 1 to 2 days during that window gives the best odds. "Saving up" by abstaining for long stretches actually works against you.
- The window is roughly 6 days, ending on ovulation day.
- Sex every 1 to 2 days through the window beats trying to time one perfect day.
- Long abstinence to "build up" sperm lowers motility. Don't do it.
- Sperm survive a few days inside; the egg lives about a day, so aim before ovulation.
You can do everything else right and still miss, simply because of timing. Conception has a narrow window each cycle, and a lot of couples either misjudge it or overthink it into a chore. The biology is straightforward once you see it, and the practical rule is easier than most people expect.
The fertile window
An egg is only available for about 24 hours after ovulation. Sperm, on the other hand, can survive in the female reproductive tract for up to about five days under the right conditions. Put those together and you get a fertile window of roughly six days: the five days leading up to ovulation, plus ovulation day itself.
The most fertile days are the two to three days right before ovulation, because that puts healthy sperm in place and waiting when the egg is released. Aiming at or just before ovulation beats aiming after, because once the egg is gone, that cycle’s window has closed.
How often to have sex
Here is where couples tie themselves in knots trying to pinpoint one perfect day. The simpler, better strategy is frequency: have sex every 1 to 2 days throughout the fertile window. That cadence means sperm are reliably present whenever ovulation happens, which matters because ovulation timing is not perfectly predictable.
Every 1 to 2 days also keeps sperm quality high, which brings up the most common timing mistake.
Why “saving up” backfires
A lot of men assume that abstaining for a week or two before the fertile window will “build up” a stronger sample. It does the opposite. Long abstinence increases volume slightly but lets sperm age, which lowers motility, the very quality that gets a sperm to the egg. The relationship between abstinence and sperm quality is the same reason a semen analysis asks for only 2 to 5 days of abstinence, covered in how to collect a semen sample.
So skip the saving-up strategy. Regular sex through the window keeps both frequency and sperm quality where you want them. The role motility plays is explained in sperm motility explained.
Finding your window
To time the window, you need a rough sense of when ovulation happens. Common methods:
- Ovulation predictor kits, which detect the hormone surge a day or so before ovulation.
- Cycle tracking, estimating ovulation as roughly 14 days before the next expected period.
- Basal body temperature and cervical mucus changes, which give additional signals.
No method is perfect, which is exactly why the every-1-to-2-days approach is forgiving. You do not have to nail the day if you are covering the window.
Where the man fits
Timing is only half the equation. The sperm arriving during that window still need to be there in sufficient number and quality. If a couple has timed things well for several cycles without success, checking the man’s side is the efficient next move, and a semen analysis is the quick way to do it. How long to try before testing is in how long it should take to conceive.
Check the man's side
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Order the RSA test →FAQ
When are the most fertile days? The two to three days right before ovulation, within a fertile window of about six days that ends on ovulation day.
How often should we have sex to conceive? Every 1 to 2 days through the fertile window. That keeps sperm present for ovulation and maintains sperm quality.
Should we save up sperm for the fertile window? No. Long abstinence lowers motility. Regular sex every 1 to 2 days is better than abstaining to “build up.”
How long do sperm survive? Up to about five days inside the female reproductive tract under good conditions, which is why sex before ovulation works. The egg itself lasts about a day.
We are timing it right but not conceiving. What now? If several well-timed cycles pass without success, test both partners. A semen analysis is the quick first step for the man. See when to seek evaluation for the thresholds.
Sources
- American Society for Reproductive Medicine. The fertile window and intercourse frequency.
- Mayo Clinic: Getting Pregnant. Timing and the fertile window.
- Cleveland Clinic: Ovulation. Ovulation timing and fertility.
Undeez is not a medical provider. Talk to a physician about your situation and any fertility concerns.
