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Pregnancy

How to Calculate When Pregnancy Occurred

Olivia Prete
· · Updated Jan 16, 2026 · 2 min read
Pregnancy is an exciting time for any couple. Whether your baby was planned or a pleasant surprise, you'll have many questions. You'll probably want to know when the baby was conceived as well as the baby's due date. While both dates are an estimate based on a woman's menstrual cycle, it can give you and your health care provider greater insight into time lines and is a great way to track the health and growth of your baby.

 

Things You'll Need

  • Calendar
 

4 Steps To Calculate When Pregnancy Occurred

Calculate When Pregnancy

1. Determine When Your Menstrual Cycle Began

This means knowing the first day of your last period. Write down the date or circle it on a calendar.

 

2. Take A Pregnancy Test 28 Days From The First Day Of Your Last Period

If it confirms that you are indeed pregnant, you can calculate when conception occurred.

 

3. Count 280 Days, Starting From The First Day Of Your Last Period

This is when the baby is due. Circle it on the calendar.

 

4. Count 266 Days Backward From The Due Date

This is the date the baby was most likely conceived.

 

Tips and Warnings
  • Conception usually takes place halfway through the menstrual cycle, or 14 days after the first day of your period.
  • Remember that all calculations are based on a typical 28-day cycle. Adjust if your cycle is longer.
 

You Might Also Like : How to Conceive a Boy : Best Ways

 

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Written by

Olivia Prete

For the past 5 years, she has been sharing her thoughts and experiences through her blog, covering topics ranging from personal development to pop culture. Olivia's writing is honest, relatable, and always thought-provoking.

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