All tools
Conception calculator
The likely day a baby was conceived, from the last period or the due date, and the days it could have been. Free, with no account or uploads.
When conception likely happened
Type the first day of your last period, or your due date. It is an estimate of a few days, not one day.
Counting from
Last periodDue date given
From the first day of one period to the first day of the next.
Type a date to see the answer.
This is arithmetic on your numbers, not medical advice; ask a doctor, nurse or midwife about your own health. Worked out in your browser; nothing you type is sent anywhere or kept, and this page has no adverts.
A little help along the way
Follow these steps. Every option is explained underneath. Everything runs in your browser; nothing is sent anywhere or kept.
- Say what you want to work outA due date, how far along you are, the conception date, or your fertile days.
- Say what you are counting fromYour last period, a due date you were given, conception, an IVF transfer or a scan.
- Type the dateWith your usual cycle length for a period, the embryo's age for IVF, or the age a scan gave.
- Read the answerIn words, with the rule it was counted by; add a due date to your calendar.
Questions people ask
- How is the conception date found?
- Ovulation is usually about 14 days before the next period, so the page counts from your last period and cycle length, or 266 days back from a due date.
- Can it tell me the exact day?
- No. Sperm can live up to five days, so conception can have been on any of about six days, and cycles vary; it is an estimate.
- Can it tell who the father is?
- No. Dates cannot show that; only a DNA test can.
This page is the Pregnancy calculator, opened for this one job; every other tool it has is one press away. Each of its settings is explained on the Pregnancy calculator's own page.
Read the step-by-step guide