How Does the Period Calculator Work?

The calculator uses simple math. Here is how it finds each date.

• Next period date = first day of your last period + your cycle length
• Ovulation day = your next period date minus 14 days
• Fertile days = the 5 days before ovulation plus the ovulation day

Example

Riya's last period started on 1 October. Her cycle is 28 days long. Her period lasts 5 days.

• Her next period will likely start on 29 October and end around 2 November.
• She will likely ovulate around 15 October.
• Her fertile days are about 10 October to 15 October.

How do I find my cycle length?

Count the days from the first day of one period to the day before your next period starts. Do this for 3 months. Then add the numbers and divide by 3. This gives you your average cycle length.

What Is the Menstrual Cycle?

The menstrual cycle is the monthly change your body goes through to get ready for a possible pregnancy. Hormones control it. Each cycle starts on the first day of your period. It ends on the day before your next period starts.

The cycle has 4 phases.

1. Menstrual Phase (Period Days)

This is when you bleed. The lining of the uterus comes out of the body through the vagina. It usually lasts 3 to 7 days. You may feel cramps, back pain or tiredness.

2. Follicular Phase

This phase starts on the first day of your period and goes on until ovulation. The body gets an egg ready. The lining of the uterus starts to grow thick again. Many people feel more energy in this phase.

3. Ovulation Phase

The ovary lets go of an egg. This usually happens about 14 days before your next period. The egg lives for about 12 to 24 hours. This is the time when the chance of getting pregnant is highest.

4. Luteal Phase

This phase starts after ovulation and lasts until your next period. It is usually about 14 days long. If there is no pregnancy, hormone levels drop. This is when many people feel PMS signs like bloating, mood swings or sore breasts.

What Is a Normal Period Cycle?

A normal cycle for adults lasts 21 to 35 days. The average is about 28 days. But only some people have a cycle of exactly 28 days. A cycle of 24 or 32 days is also normal.

A normal period lasts 2 to 7 days.

For teens, cycles can be longer, up to 45 days. This is common in the first few years after the first period. The cycle often becomes more regular with time.

It is also normal for your cycle to change by a few days from month to month.

Can I Use It If My Periods Are Irregular?

Yes, you can. But the dates will be less exact.

Your periods may be irregular if:

• Your cycle is shorter than 21 days or longer than 35 days
• Your cycle length changes by more than 7 to 9 days from month to month
• You skip periods often

Tip: Track your periods for 3 to 6 months. Use the average cycle length in the calculator. This will give you better results. You can also track your periods for free on WhatsApp. Just send "Hi" to +91 97188 66644.

Why Is My Period Late?

A period is usually called late when it has not started 5 or more days after the date you expected. A late period is common and is often not a cause for worry.

Common reasons include:

• Pregnancy. If you had sex, take a home pregnancy test.
• Stress. Exams, work or big life changes can delay your period.
• Weight change. Losing or gaining a lot of weight can affect your cycle.
• Too much exercise. Very hard training can stop or delay periods.
• PCOS. Polycystic ovary syndrome is a common hormone problem that can cause irregular periods.
• Thyroid problems. Both an overactive and an underactive thyroid can change your cycle.
• Medicines. Some medicines, including birth control pills, can change your period.
• Breastfeeding. Periods may not come back for some months after childbirth.
• Illness or travel. Being sick or changing time zones can shift your dates.

Signs Your Period Is Coming

Many people notice signs 1 to 2 weeks before their period. These signs are called PMS (premenstrual syndrome). They usually go away a few days after the period starts.

Common signs include:

• Cramps in the lower belly
• Bloating or a full stomach
• Sore or swollen breasts
• Pimples or acne
• Feeling tired
• Mood swings or feeling low
• Food cravings
• Headache or back pain

Get Ready for Your Next Period

Once you know your dates, you can plan ahead. Keep your period products ready a few days before your period is due. Here are Sirona products that can help before, during and after your period.

For Period Days

Pick the product that feels right for your body and your flow.

• Sirona Select+ Rash Free Sanitary Pads: Cottony-soft pads with wide cover for heavy flow. Change your pad every 4 to 6 hours, or sooner on heavy days.
• Sirona Comfort+ XXL Sanitary Pads: Longer pads that give more cover at night.
• Sirona Reusable Sanitary Pads: Cloth pads you can wash and use again. A good pick if you want less waste.
• Sirona Menstrual Cup: A soft cup made of medical-grade silicone. It collects period blood and can be worn for up to 8 hours.
• Sirona Reusable Menstrual Disc: A flat, soft disc that sits higher inside the body. Some people find it more comfortable than a cup.
• Sirona Tampons, Mixed Flow: Tampons for light and heavy days in one pack. Change a tampon every 4 to 8 hours.
• Sirona Applicator Tampons: Tampons with an applicator for easy use if you are new to tampons.
• Sirona Disposable Period Panties: Wear them like underwear and throw them away after use. Great for heavy nights and travel.
• Sirona Reusable Period Panty: Washable underwear that soaks up period blood. Wear it alone on light days or with a cup or pad on heavy days.

For Light Days and Spotting

• Sirona Dry Comfort Panty Liners: Thin cotton liners for the first and last days of your period, or for spotting.

For Period Cramps

• Sirona Feminine Pain Relief Patch: A herbal, drug-free patch. Stick it on your lower belly to help ease cramps at home, school or work.
• Sirona Electric Hot Water Bag: Heat on the belly can help relax the muscles and ease period pain.
• Sirona Cramp Comfort Kit: A ready kit to help you get through painful period days.

For Cup and Disc Care

• Sirona Electric Menstrual Cup Sterilizer: Cleans your cup or disc with steam after each period.
• Sirona Natural Menstrual Cup Wash: A gentle wash that is safe for silicone cups and discs.

For Staying Clean and Fresh

• Sirona Intimate Wet Wipes: Alcohol-free wipes to feel fresh when you cannot wash.
• Sirona Period Stain Remover Wipes: Wipe away period stains from clothes when you are out.
• Sirona Sanitary Disposal Bags: Wrap and throw away used pads and tampons in a clean way.

For a First Period

• Sirona First Period Kit: A simple kit to help girls feel ready for their first period.
• Sirona Teens Period Pants: Soft, leak-proof period pants made for teens.

Keep a Period SOS Kit in Your Bag

Periods do not always come on the exact date. Keep a Sirona Period SOS Kit in your school bag, office bag or purse. Then you are ready even if your period comes early.

Track Your Period on WhatsApp

Do not want to check your dates every month? Use the free Sirona Period Tracker on WhatsApp. Just send "Hi" to +91 97188 66644 on WhatsApp. Share your period details, and the tracker will remember them. It sends you reminders and your next cycle dates.

Start tracking on WhatsApp

When Should You See a Doctor?

Most changes in your period are normal. But talk to a doctor if:

• You have not had a period for 3 months and you are not pregnant
• Your period lasts more than 7 days
• You need to change your pad or cup every 1 to 2 hours because of heavy bleeding
• You pass blood clots that are about 2.5 cm or bigger
• Your cramps are so bad that you cannot do daily tasks
• Your cycle is shorter than 21 days or longer than 35 days most of the time
• You bleed between periods or after sex
• You have not had your first period by age 15

A Note from Sirona

At Sirona, we want you to know your body better. This calculator gives you a reliable guide to your next period, ovulation day and fertile days. It works best when your periods are regular.

But every body is different. Your dates can change because of stress, illness, health conditions like PCOS or thyroid problems, or some medicines. So please treat these dates as a guide, not a promise.

This calculator is not a birth control method. Do not use it to avoid pregnancy. It also does not replace advice from a doctor. If something feels wrong, please talk to a doctor.