Seven free calculators for trying to conceive and for pregnancy. Find your conception date, work back from a due date or scan to the day you conceived, work out your due date, see your fertile window and implantation window, check an hCG result and check how much weight to gain. Nothing you enter leaves your browser.
Work back from your last period, your due date or an ultrasound to the day you most likely conceived, the days that could have led to it, and when implantation happened.
Work out when you most likely conceived. Start from the first day of your last period, your due date or a conception date you already know, and you get a window of a few days either side.
Find your due date, see how many weeks pregnant you are today and get the dates of the scans, tests and milestones ahead.
See your estimated ovulation day, fertile window and best days to try, with a plain guide to when to have sex and what your chances are each cycle.
See when implantation is most likely, the full 6 to 12 day window after ovulation and the first day to take a pregnancy test.
Enter a blood test result to see which weeks of pregnancy it fits, or enter two results to check the 48 hour rise, the doubling time or a fall.
See the recommended weight gain for your whole pregnancy and for your week, in kilograms, pounds or stones, for one baby or twins.
| Your situation | Calculator |
|---|---|
| I want to know when I conceived | Conception calculator: when did I get pregnant? |
| I know my due date or my scan results and want the conception date | Pregnancy conception date calculator |
| I have a positive test and want my due date | Pregnancy due date calculator |
| I want to know how many weeks pregnant I am | Pregnancy due date calculator |
| I am trying to conceive and want to time sex | Best time to get pregnant calculator |
| I want to know my chances of getting pregnant this cycle | Best time to get pregnant calculator |
| I want to know when implantation happens | Implantation calculator: when does implantation happen? |
| My blood test shows an hCG number | hCG calculator: how many weeks pregnant am I? |
| I want to know how much weight to gain | Pregnancy weight gain calculator |
Calculators give estimates. A pregnancy test confirms a pregnancy, and an early ultrasound gives the most accurate due date. If you are not sure whether to test yet, our guide to when to take a pregnancy test explains the timing, and the week by week pregnancy timeline shows what happens after your dates are set.
Pregnancy is dated from the first day of your last period, which is why you count as two weeks pregnant on the day you conceive. The conception and due date calculators use that standard, adjust for cycle length and show a window because ovulation and conception can fall a few days either side of the estimate.
The fertile window and implantation calculators work backwards from your next period, since ovulation tends to happen about 14 days before it, and the implantation calculator then adds 6 to 12 days. The hCG calculator compares a blood test result with published ranges and guidance, and the weight gain calculator applies national recommendations to your height and starting weight. Every page lists its sources.
None of the calculators needs your name or email, and none of them replaces advice from your care team.
Short answers about choosing and using a pregnancy calculator.
An early ultrasound gives the most accurate dating, and every calculator here is an estimate that starts from a date or a number you provide. Each page shows how it works and which sources it uses, so you can judge it for yourself. If a scan and a calculator disagree, your care team uses the scan.
No calculator can tell you whether you are pregnant. A pregnancy test does that, and a blood test or scan confirms it. Our guide to when to take a pregnancy test explains the timing, and the calculators then help you work out your dates.
Use the conception calculator. Enter the first day of your last period, your due date or a conception date you already know. Conception usually happens about 14 days after the first day of your last period, and the calculator shows a window of a few days either side.
Pregnancy is counted from the first day of your last period, so you are already about two weeks pregnant on the day of conception. The due date calculator counts the weeks and days for you and shows the trimester.
No. They run in your browser, and nothing you type is sent to us. A session store in your own tab keeps your entries until you close the tab, so you can move between calculators.
Yes. They are free, they have no sign-up and they never ask for your name or email.
