Late Period Calculator — How Late Am I?
If your period hasn't arrived, enter your last period date and cycle length to see your expected date and how many days late you are. A period is usually considered late once you're more than 5 days past the expected date. This page explains the common reasons for a late or missed period and when a pregnancy test will give a reliable answer.
Enter your last period date and press Calculate to see your cycle predictions.
Tools that pair well with this one.
Eight more calculators families use alongside this — all free, no account needed.
Frequently asked questions
When is a period officially considered late?+
A period is generally 'late' once you are more than 5 days past your expected date, and 'missed' once you reach about 6 weeks from your last period with no bleeding. A one-off late period is usually nothing to worry about.
Why is my period late if I'm not pregnant?+
Common non-pregnancy causes include stress, sudden weight change, intense exercise, travel and time-zone changes, illness, poor sleep, thyroid problems, PCOS, and starting or stopping hormonal contraception. Perimenopause can also lengthen cycles.
When should I take a pregnancy test if my period is late?+
If you're sexually active, take a home pregnancy test from the day after your missed period, and repeat after a week if it's negative but your period still hasn't come. Testing first thing in the morning gives the most reliable result.
When should I see a doctor about a late or missed period?+
See a gynaecologist if you miss three or more periods in a row (and aren't pregnant), your periods are consistently irregular, or a late period comes with severe pain, unusual discharge, or other new symptoms.
How does the period calculator work?+
Enter the first day of your last period and your average cycle length (28 days is typical, but 21–35 days is also normal). The calculator counts forward to predict your next 6 period start dates, plus the ovulation day and fertile window within each cycle. The prediction assumes a roughly regular cycle.
What's a normal menstrual cycle length?+
Any cycle between 21 and 35 days is considered normal. The 28-day cycle is a popular average, not a universal standard. What matters more is consistency — if your cycle length varies by less than 7–9 days month to month, you're considered regular.
Does this period calculator work for irregular periods or PCOS?+
It gives a rough estimate, but predictions are less accurate when cycles vary. With PCOS, post-pregnancy, perimenopause, or chronic stress, cycles often shift by 7+ days. For irregular cycles, track 3–6 months of actual dates to find your personal average, and don't rely on calendar predictions for contraception.
Is this a substitute for a doctor?+
No — it's a calendar tool. If you have heavy bleeding, severe pain, missed periods for 3+ months (when not pregnant), bleeding after menopause, or any new symptoms, see a gynaecologist. The calculator helps you track your cycle; it doesn't diagnose conditions.