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Pregnancy test calculator: when to take a test

Testing too early is the most common reason for a confusing result. Enter your dates to see when implantation usually happens and which day gives the most reliable answer.

When can you take a pregnancy test?

The most reliable day to test is the first day of your missed period, or any day after it. That is about 14 days after ovulation. Some tests say they can detect a pregnancy a few days earlier, but they are less reliable, and a negative result that early may simply mean it is too soon.

If your cycles are irregular, it can be hard to know when your period is due. In that case, test at least three weeks after you last had unprotected sex.

How a pregnancy test works

Home tests detect a hormone called hCG in your urine. Your body only makes hCG after a fertilised egg has implanted in the lining of the womb, which usually happens 6 to 12 days after ovulation. Levels then rise quickly, roughly doubling every two to three days in the first weeks, so a test that is negative at 10 days past ovulation can be clearly positive a few days later.

What is implantation bleeding?

Some people notice a little light spotting, often pink or brown, around the time the egg implants. It is usually much lighter than a period and lasts from a few hours to a couple of days. Many people have no bleeding at all, so its absence tells you nothing. If the bleeding is heavy, bright red or painful, contact your doctor or midwife.

Getting the most accurate result

• Follow the instructions in the box. Time and the amount of urine matter.
• Most tests work at any time of day. Some makers suggest first-morning urine if you test early, because it is more concentrated, so check the leaflet.
• Check the expiry date and read the result at the time the instructions say, not later.
• If you get a negative result but your period has not arrived, test again after three to seven days.
• A faint line on most tests is usually a positive result. Test again in a couple of days if you are unsure.

What to do next

If your test is positive, contact your doctor or midwife to book your first appointment, and start taking folic acid if you have not already. Our guides can help: early signs of pregnancy and testing, folic acid and prenatal vitamins and what to expect at your first appointments.

If you have a positive test and one-sided lower abdominal pain, shoulder-tip pain, dizziness or vaginal bleeding, seek urgent medical help. Read about the symptoms of an ectopic pregnancy. If you are still trying, the ovulation calculator shows your fertile window.

Official guidance: NHS: doing a pregnancy test.