Tools · Pregnancy

When to Take a Pregnancy Test: Calculator and Early Signs Checklist

See when to take a pregnancy test from your last period or the date you had sex, based on NHS (UK) or FDA and OWH (US) advice. Plus an early signs checklist.

Quick answer: In the US, the FDA says to test 1 to 2 weeks after a missed period for the most reliable result, and the Office on Women's Health (OWH) says results may be more accurate if you wait until after the first day of your missed period. In the UK, the NHS says most tests can be used from the first day of a missed period. With irregular periods, the OWH suggests counting four weeks from the time you had sex; if you don't know when your period is due, the NHS says to test at least 21 days after you last had unprotected sex.

Reviewed by: Whispie Editorial Team Evidence-Based Parenting Research

Published: 2026-09-25

This article is for general information and is not a substitute for professional medical advice. Always consult your pediatrician or doctor about your child.

Sources: WHO, CDC, AAP and NHS guidance. Recommendations differ between countries — for local advice see the NHS or CDC.

See how we research and review →

Enter the first day of your last period and your cycle length, and the calculator shows when your next period is due and the dates to test. If your periods are irregular or you don't know when the next one is due, choose 'Irregular / I don't know' and enter the date you last had unprotected sex (with the United States selected, you can also enter the first day of your last period).

The dates follow the guidance for the country you pick: the Office on Women's Health (OWH) and the FDA in the United States, and the NHS in the United Kingdom. Below the calculator you'll find the NHS list of early signs, when to get medical help, and first steps if your test is positive.

Where do you live?

First day of your last period Cycle length (days) 21 to 45 days. Not sure? Use 'Irregular / I don't know'.

When to get medical help

If you think you might be pregnant and have abnormal vaginal bleeding or pain in your lower belly or pelvis, contact your provider (MedlinePlus).
During pregnancy, the CDC says to seek medical care immediately for warning signs such as vaginal bleeding or fluid leaking, severe belly pain that doesn't go away, dizziness or fainting, and severe nausea and throwing up.
If an ectopic pregnancy ruptures, symptoms may get worse, for example severe, sharp and sudden pain in the lower belly, fainting or feeling faint, or pain in the shoulder area. A rupture needs emergency medical help (MedlinePlus).
When you get care, tell them you are pregnant or were pregnant within the last year (CDC).

In an emergency, call 911 or your local emergency number (MedlinePlus).

If your test is positive

Call your doctor right away to schedule an appointment (OWH). MedlinePlus says to see your provider as soon as possible to make sure you get the right care.
Your doctor can use a blood test, or a more sensitive test along with a pelvic exam, to tell for sure whether you are pregnant (OWH).
Seeing your doctor early in pregnancy means you can begin prenatal care, and it can help you and your baby stay healthy (OWH).

Frequently Asked Questions

When should I take a pregnancy test?

In the US, the FDA says to test 1 to 2 weeks after a missed period for the most reliable result, and the Office on Women's Health (OWH) says results may be more accurate if you wait until after the first day of your missed period. In the UK, the NHS says most tests can be used from the first day of a missed period. Some very sensitive tests can be used even before you miss a period (NHS), but the OWH says the earlier you test, the harder it is for a test to detect hCG. The calculator turns these into dates for you.

Should I take a pregnancy test in the morning?

US and UK advice differ here. MedlinePlus says to test your first morning urine, because it usually has more hCG than urine later in the day, and the FDA and the Office on Women's Health (OWH) say first morning urine can improve accuracy. The NHS says you can use urine collected at any time of day, and it doesn't have to be in the morning.

Can a pregnancy test be negative if I'm pregnant?

Yes. The Office on Women's Health (OWH) says women sometimes get false-negative results when they test too early, and the NHS says a positive result is almost certainly correct, but a negative result is less reliable. If you still think you're pregnant, the NHS says to wait a few days and test again, and to speak to a GP if the second test is also negative and your period hasn't arrived. MedlinePlus says hCG rises every day in early pregnancy, so it's a good idea to repeat the test a week after the first one, and to call your provider if two home tests are negative but you still think you're pregnant.

When should I test if my periods are irregular?

The Office on Women's Health (OWH) suggests counting 36 days from the start of your last period, or four weeks from the time you had sex. If you don't know when your next period is due, the NHS says to do the test at least 21 days after you last had unprotected sex. Choose 'Irregular / I don't know' in the calculator to see these dates.

Can you have pregnancy symptoms before a missed period?

The Office on Women's Health (OWH) says symptoms such as headache, fatigue and breast tenderness can occur even before a missed period, and MedlinePlus says the most common sign of early pregnancy is a missed period. The NHS says early signs usually start when you're around 4 to 6 weeks pregnant, and that if you think you might be pregnant, you can find out by doing a pregnancy test.

Sources: Office on Women's Health (HHS) — Pregnancy tests · Office on Women's Health (HHS) — Knowing if you are pregnant · FDA — Pregnancy (home use tests) · MedlinePlus — Pregnancy test · MedlinePlus — Ectopic pregnancy · MedlinePlus — Recognizing medical emergencies · CDC — Urgent maternal warning signs (HEAR HER) · NHS — Doing a pregnancy test · NHS — Signs and symptoms that might mean you're pregnant · NHS — Ectopic pregnancy: symptoms · NHS — When to call 999 · NHS — What to do when you find out you're pregnant · NHS — Refer yourself for NHS pregnancy care · NHS — Antenatal (pregnancy) care and appointments