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When might my next period start?
Estimate your next period, likely ovulation date and fertile window from the cycle information you enter.
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FREE MENSTRUAL CYCLE CALCULATOR — USE IT NOW
Estimate your next period and cycle dates
Enter basic information about your latest period to see an estimated next-period window, ovulation date and fertile window.
Your estimated cycle
Next estimated period
Estimated ovulation
Estimated fertile window
Latest period dates
These dates show your estimated cycle timing based on the information entered. For pregnancy prevention, use a recognised contraceptive method.
*The information submitted in this calculator is not stored.
Cycles are personalA 28-day cycle is a common reference point. Cycle timing and period length can vary between women and from month to month.
Changes may be worth discussingSpeak with a gynaecologist if periods are repeatedly absent, suddenly change, are unusually heavy, cause severe pain, or regularly last outside your normal pattern.
A HELPING HAND FOR WHAT COMES NEXT
Would you like to keep going?
Talk through the estimate with Aura, or keep it with your dates so it is easy to find next time.
Turn one estimate into a clearer cycle history.
Create a free ParentAura+ App account to keep this dated result, follow changes and build a clearer report over time.
- ✓Keep period dates, flow and symptoms in one private place.
- ✓See how cycle length changes from month to month.
- ✓Build clearer reports as your history grows.
Your result is still here. Please open ParentAura+ separately to continue.
WHAT YOUR ESTIMATE SHOWS
A helpful starting point
- ✓Show an estimated next-period window from your latest period and usual cycle length.
- ✓Place likely ovulation and fertile-window dates on the same simple timeline.
- ✓Give you a useful starting point for planning this cycle.
USEFUL TO KNOW
Keep this in mind
- —Predict the exact day your period or ovulation will happen.
- —Explain repeated missed periods, very heavy bleeding or severe pain.
- —Diagnose pregnancy, PCOS or another health condition.
This is an estimation based on the details entered. Please consult your gynaecologist to confirm the outcome when it relates to your care.
UNDERSTANDING YOUR CYCLE
Your menstrual cycle is more than your period
A menstrual cycle starts on the first day of one period and ends the day before the next period begins. Tracking the dates can help you anticipate bleeding, understand recurring symptoms and recognise changes in your usual pattern.
This is the date used to begin each cycle, even if bleeding continues for several days.
Many adult cycles fall between approximately 21 and 35 days, and small month-to-month changes can occur.
Period length counts bleeding days. Cycle length counts from the start of one period to the start of the next.
Several recorded cycles provide a more useful picture than a single calendar estimate.
What happens during the menstrual cycle?
The menstrual cycle is a repeating sequence of hormonal and physical changes that prepares the body for a possible pregnancy. It includes menstruation, development of an egg, ovulation and the time after ovulation.
Follicular phase
This begins on the first day of the period. The uterine lining is shed, estrogen gradually rises and follicles in the ovaries develop. One follicle may release an egg at ovulation. The length of this phase can vary considerably.
Luteal phase
This begins after ovulation. Progesterone helps prepare the uterine lining for a possible pregnancy. If pregnancy does not occur, estrogen and progesterone fall and the next period begins.
How to calculate cycle length
Mark the first day of one period, then mark the first day of the following period. Count the days from the first date up to—but not including—the second date. That number is the cycle length. Repeat this for several cycles and calculate an average if the lengths are reasonably consistent.
To make a simple next-period estimate, add the usual cycle length to the first day of the most recent period. The calculator also estimates ovulation by counting back approximately 14 days from the predicted next period. The time between ovulation and the next period is not exactly 14 days for every woman, so the result remains approximate.
How long can a period last?
Bleeding patterns differ. A period commonly lasts several days, often around two to seven days, but your usual pattern matters. Spotting is not always the same as the first day of full menstrual bleeding, so consistent recording helps.
Speak with a gynaecologist if something changes significantly. Seek advice for very heavy bleeding, bleeding lasting much longer than usual, severe pain, dizziness or fainting, periods that repeatedly disappear, or a sudden persistent change in your normal cycle.
What can influence cycle timing?
Stress, illness, travel, major sleep changes, significant weight change, intense exercise, breastfeeding, adolescence, perimenopause, medicines and conditions such as PCOS or thyroid disorders can affect cycle timing. Tracking shows the pattern, while a medical professional can assess possible causes when needed.
If cycles are frequently shorter than about 21 days, longer than about 35 days, or vary widely, tracking can provide useful information to discuss with a gynaecologist.
Why might a period arrive later than expected?
A calculator predicts from an average, but an individual cycle may be longer. Pregnancy is one possibility after unprotected sex, while stress, illness, travel, major sleep or weight changes, intense exercise, breastfeeding, changes in contraception, PCOS, thyroid conditions and perimenopause can also alter timing.
A later-than-expected period can happen for different reasons. If pregnancy is possible, use an appropriately timed pregnancy test. Professional support can help when periods remain absent, repeatedly unpredictable or substantially different from your usual pattern.
How can I recognise an irregular pattern?
Small differences between cycles are common. A pattern may be considered irregular when periods are repeatedly fewer than about 21 days or more than about 35 days apart, when the gap changes considerably from one cycle to the next, or when bleeding is unusually heavy or unpredictable.
A calculator becomes less accurate when cycles vary. Recording several start dates, bleeding days and symptoms is still useful because it turns “my periods are irregular” into a dated history that a gynaecologist can review.
Symptoms around a period
Menstrual cramps
Cramping can occur as the uterus contracts. Mild discomfort is common, but pain that interrupts normal activities, becomes suddenly worse or is not helped by usual measures deserves medical attention.
Tiredness
Hormonal changes may affect energy. Very heavy periods can also contribute to iron deficiency and fatigue, so persistent exhaustion alongside heavy bleeding should be discussed with a gynaecologist.
Bloating
Hormonal changes can affect fluid balance and digestion. Speak with a clinician if bloating is severe, persistent or continues well beyond the usual cycle pattern.
Mood changes
Some women notice irritability, sadness, anxiety or emotional sensitivity before a period. Track timing and severity. Major mood symptoms or changes affecting daily life need professional support.
Skin and breast changes
Hormonal fluctuations may be linked with temporary acne and breast tenderness. New or persistent breast symptoms deserve individual assessment from a qualified medical professional.
Can pregnancy happen soon after a period?
Yes, particularly with shorter cycles or longer bleeding. Sperm can remain alive for several days, and ovulation may happen earlier than a calendar estimate predicts. For pregnancy prevention, use a recognised contraceptive method.
Why ongoing tracking is more useful
One estimate assumes that the entered cycle length represents your usual pattern. Tracking several months can show average cycle length, variation, bleeding duration and recurring symptoms. This makes the dashboard more personal and provides clearer information if you later speak with a gynaecologist.
Questions about periods and the ParentAura App
When is a menstrual cycle considered irregular?
Cycle length naturally varies, but a recurring pattern of cycles shorter than about 21 days, longer than about 35 days, missed periods or large changes from one month to the next is worth discussing with a gynaecologist. Recording several cycles helps you see whether the change is occasional or repeating.
Why might my period arrive earlier or later than expected?
Stress, illness, travel, sleep changes, weight changes, breastfeeding, contraception, PCOS, thyroid conditions and pregnancy can all affect timing. If pregnancy is possible, take a pregnancy test at the appropriate time. Seek professional support for persistent or significant changes.
Can I become pregnant soon after my period?
Yes. This can happen when ovulation occurs early, especially with shorter cycles or longer bleeding. Sperm can remain alive for several days, so period dates alone should not be used for contraception.
What does the ParentAura Period Calculator show?
Enter the first day of your latest period and your usual cycle length to see an estimated next-period date, cycle phases and fertile-window timing.
How does the Period Tracker help with irregular cycles?
Instead of relying on one month, the App compares the period dates and symptoms you record across multiple cycles. It shows your shortest, longest and average recorded cycle so your personal pattern becomes easier to understand.
A HELPING HAND FOR FUTURE DATES
My Period & Cycle Tracker
The matching ParentAura+ App keeps the dates and updates you choose to add together, so your own pattern becomes easier to follow over time.