When to Take a Pregnancy Test Calculator
Enter the first day of your last period and your usual cycle length to see the first day a standard home pregnancy test is reliable. That day is the first day of your missed period. The calculator also shows when a negative result is easier to trust.
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From the first day of one period to the first day of the next. Leave it at 28 if you are not sure.
Enter the first day of your last period to see when a home pregnancy test is reliable.
This is general information, not medical advice. It cannot take your own health history into account. For anything that worries you, speak to a doctor, midwife or pharmacist.
How it works
The earliest reliable test day = first day of your last period + your cycle length. That is the day your next period is due, so if it does not come, it is the first day of your missed period. The NHS says most pregnancy tests can be used from this day.
The second date is 7 days later. Home tests look for a hormone called hCG in your urine. Your body only starts making hCG once a fertilised egg has attached to the womb, about 6 to 10 days after the egg is fertilised, and the level then rises quickly. A test taken too early can be negative even when you are pregnant. MedlinePlus (US National Library of Medicine) says urine tests are 97 to 99% accurate a week or two after a missed period.
Estimated ovulation is the day your period is due minus 14 days. It is shown so you can see how the dates fit together: the first reliable test day is about 2 weeks after ovulation.
What it cannot tell you
- The dates depend on your cycle being close to its usual length this month. If you ovulated later than usual, the first reliable day is later too. If you do not know when your period is due, the NHS advice is to test at least 21 days after you last had unprotected sex.
- A positive result is almost certainly correct. A negative result is less certain, mostly because of testing too early. If your test is negative and your period still has not come, test again after a few days, and speak to a doctor if a second test is negative and you still have no period.
- Some tests are sold for use a few days before a missed period. They can pick up some pregnancies early, but they miss more at that stage. Always follow the instructions in the box.
- The calculator cannot tell you if you are pregnant. If you have a positive test with severe pain low in your tummy, pain in the tip of your shoulder, or heavy bleeding, get urgent medical help.
Apps that do this for you
A calculator answers once. These apps keep track over time. Compare all period tracking apps.
Clue
A period tracker: cycle tracking with predictions for your period, PMS and ovulation.
Cycles
A period tracker for iPhone: predict your periods and fertile days and share your cycle phases with a partner.
Euki
A period tracker: log your cycle and sexual health, with your entries kept on your phone.
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Common questions
You can take most home pregnancy tests from the first day of your missed period. Some sensitive tests can be used a few days earlier, but a negative result that early is less reliable. If you do not know when your period is due, the NHS says to test at least 21 days after you last had unprotected sex.
A standard home pregnancy test is reliable about 14 days after ovulation, which is around the day your period is due. Before that, the level of the pregnancy hormone hCG is often too low to detect. Testing earlier can give a negative result even if you are pregnant.
Yes, a pregnancy test can be negative when you are pregnant, most often because it was taken too early. The hormone hCG only appears after the fertilised egg attaches to the womb, and it takes a few more days to reach a level a test can find. If your period does not come, test again in a few days.
No, you do not need to take a pregnancy test in the morning once your period is late. The NHS says you can test a urine sample collected at any time of day. If you test before your period is due, the first urine of the day is the most concentrated, so check the instructions for your test.
Home pregnancy tests are about 97 to 99% accurate when used a week or two after a missed period and when the instructions are followed. A positive result is almost always right. A negative result is less reliable, especially if you test early.