Cycle · Missed period
Period late calculator.
Enter the first day of your last period, your usual cycle length and today's date to see how many days late your period is.
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Period Late Calculator: how it works
Your period is late by today's date minus the date it was expected, and the expected date is the first day of your last period plus your usual cycle length. If your last period began on 1 September 2026 and your cycle is 28 days, the next is expected on 29 September, so on 3 October it is 4 days late and you are on cycle day 33.
Cycle length is counted from the first day of one period to the first day of the next, so the expected start is the last period start plus your cycle length in days. The NHS says periods usually come around every 28 days, but a gap of 21 to 35 days is common, and a period is irregular if the gap is under 21 or over 35 days. If your cycle is irregular, the expected date is an average and your real date can easily fall days either side of it; use the Cycle Length Average and Regularity Calculator to see your own range.
On testing, the NHS says you are most likely to get a reliable result from the first day of a missed period, and that a negative result is less reliable if you test too early. A missed period is often an early sign of pregnancy, but it can also be caused by stress, weight changes, exercise, hormonal contraception, thyroid problems and other conditions. See a clinician for a late period together with pain, heavy bleeding or other symptoms.
Worked example. Last period started 1 September 2026, usual cycle 28 days. Expected start = 1 September + 28 days = 29 September. Today is 3 October, so the period is 3 October - 29 September = 4 days late. Cycle day today is 33 (1 September is day 1).
Frequently asked questions
How many days late is my period?
Days late = today minus your expected period date, where the expected date is your last period start plus your usual cycle length. A last period on 1 September and a 28 day cycle gives an expected date of 29 September.
When should I take a pregnancy test if my period is late?
The NHS says most pregnancy tests can be used from the first day of a missed period. A negative result is less reliable if you test too early, so retest after a few days if you still think you could be pregnant.
What if my cycle is irregular?
Then the expected date is only a guide. The NHS defines irregular as a gap under 21 days or over 35 days. Enter your usual or average cycle length, and see the cycle average page to work out your range.
What can make a period late other than pregnancy?
The NHS lists stress and anxiety, big weight changes, too much exercise, some hormonal contraception, thyroid problems and the start of menopause among the causes of irregular periods.
When should I see a doctor about a late period?
The NHS says to see your GP if your test is negative and you have missed 3 consecutive periods. See a clinician sooner for pain, heavy bleeding or other symptoms that worry you.
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Not medical advice
Not medical advice. This tool does not diagnose anything and cannot tell you whether a pregnancy is healthy or whether a cycle is normal for you. See your clinician for heavy or unusual bleeding, pain, dizziness, or any symptom that worries you, and get urgent care for severe pain or very heavy bleeding.