Conception Calculator
When did I conceive? This free conception calculator estimates the date your baby was most likely conceived, based on your due date, the first day of your last period or an ultrasound. It also shows the window of days when sex could have led to your pregnancy.
| Detail | Dates |
|---|---|
| Likely conception window (± 2 days) | — |
| Days when sex could have led to pregnancy | — |
| Likely implantation | — |
| Reliable home pregnancy test from | — |
Healthy eating in early pregnancy
- Breakfast: 1–2 well-cooked eggs with whole wheat toast or roti and a glass of milk
- Mid-morning: seasonal fruit (banana, apple, orange) and a few almonds
- Lunch: palak or saag, daal, 1 roti and raita
- Snack: plain lassi or a fruit chaat
- Dinner: well-cooked chicken or fish, sabzi and a small portion of rice
Folic acid: if you are not already taking it, start a folic acid supplement (usually 400 micrograms a day) straight away, as advised by your doctor. It helps prevent neural tube defects and matters most in the first 12 weeks.
Important first steps
- Confirm your pregnancy with a home test, then book a visit with your doctor or gynaecologist.
- Tell your doctor about any medicines you take, as some are not safe in pregnancy.
- Avoid smoking, alcohol, raw or undercooked meat and eggs, unpasteurised milk and liver.
- Limit caffeine to 200 mg a day, about two mugs of tea or one to two cups of coffee.
- For morning sickness, try small, frequent meals, ginger, or plain crackers before getting out of bed.
- Stay active with gentle exercise such as walking, unless your doctor advises otherwise.
- Rest and drink plenty of water; tiredness is very common in early pregnancy.
Disclaimer: Conception dates are estimates. Your doctor can give a more accurate date with an early ultrasound.
When did I conceive?
For most people with a regular 28-day cycle, conception happens around two weeks after the first day of the last period, when the ovary releases an egg (ovulation). With longer or shorter cycles, it happens later or earlier. Because sperm can survive in the body for up to five days and the egg lives for 12–24 hours, the sex that led to your pregnancy could have happened up to five days before conception.
How the conception date is calculated
From your due date: conception ≈ due date − 266 days (38 weeks).
From your last period: conception ≈ first day of last period + (cycle length − 14) days. For a 28-day cycle this is day 14; for a 32-day cycle, day 18.
From an ultrasound: the pregnancy age measured on the scan is used to work back to your last period, then 14 days are added.
Example: If your due date is 8 June 2027, your most likely conception date is 15 September 2026, and the days when sex could have led to pregnancy are roughly 10–16 September 2026.
How accurate is a conception calculator?
A conception calculator gives an estimate, usually accurate to within a few days for people with regular cycles. The exact day is difficult to know because ovulation can vary from cycle to cycle, sperm can wait several days for an egg, and due dates themselves are estimates. An early ultrasound, done before about 14 weeks, gives the most accurate dating, usually within about 5–7 days.
Conception vs implantation
Conception (fertilisation) is when a sperm meets the egg, usually in the fallopian tube. The fertilised egg then travels to the womb and implants in its lining about 6–12 days later. After implantation the body starts making the pregnancy hormone hCG, which is what pregnancy tests detect. That is why tests are most reliable from the day your period is due, about two weeks after conception.
Pregnancy weeks vs weeks since conception
Doctors count pregnancy from the first day of your last period, not from conception. This means that at the moment of conception you are already considered two weeks pregnant. A pregnancy that is "8 weeks" by the doctor's count is about 6 weeks since conception. To find your due date and key dates ahead, use our Due Date Calculator; if you are planning a pregnancy, the Ovulation Calculator shows your most fertile days.
Frequently Asked Questions
How do I work out when I conceived?
Subtract 266 days from your due date, or add about 14 days to the first day of your last period if you have a 28-day cycle. This calculator does it for you and adjusts for your cycle length.
Can I get pregnant from sex a few days before ovulation?
Yes. Sperm can live for up to five days, so sex in the five days before ovulation can lead to pregnancy. The most fertile days are the two or three days before ovulation.
Can a conception calculator tell who the father is?
No. Because conception can follow sex from several days earlier, and dates are only estimates, a calculator cannot reliably show which encounter led to a pregnancy. Only a DNA paternity test can confirm this.
How soon after conception can I take a pregnancy test?
Home tests are most reliable from the first day of your missed period, around 14 days after conception. Some sensitive tests can show a positive result a few days earlier.
Is the conception date the same as the day I had sex?
Not always. Conception happens when the egg is fertilised, which can be up to five days after sex because sperm can survive in the body while waiting for ovulation.