If my first day of my last period pregnancy calculator

How do I use the pregnancy calculator?

To find out your due date, you just need to select the date of the first day of your last period on our pregnancy calculator tool, adjust your average cycle length and click 'submit’. Your cycle length is the number of days between your periods, counting the first day of your period until the day before your next period starts. 

You will then receive your estimated due date and the option to sign-up to our pregnancy email. This weekly email gives you fun pregnancy facts, useful tips and great recipe ideas to help you and your baby have the healthiest possible pregnancy.

Are you in early pregnancy? Find out all you need to know about pregnancy from week 4 onwards.

What if I have irregular periods?

If you were having irregular periods before you got pregnant, you can still use the pregnancy calculator. Just choose your average cycle length. But bear in mind that an ultrasound will be the most accurate way of predicting your due date.

How accurate is the due date?

The pregnancy calculator gives you an approximate due date. It is worked out by adding 280 days (40 weeks) to the first day of your last menstrual period. This is based on a 28-day cycle but is adjusted for longer or shorter cycles.

Your period and ovulation are counted as the first 2 weeks of pregnancy. If you have the baby on your due date, your baby has been growing for 38 weeks, not 40, but you are still classed as 40 weeks pregnant. 

Remember that only around 5% of babies are born on their due date so it’s just an estimation.  

Will I get a more accurate due date later in the pregnancy?

You will have your first appointment with the midwife, the 'booking appointment', by 10 weeks.  At that appointment, you will be offered an ultrasound scan – this is often called the dating scan.  

This scan will check how many weeks pregnant you are and work out a more accurate due date. You’ll also be able to find out whether you’re having more than 1 baby and how your baby is developing.  

But if you're impatient to know when your baby will arrive, our due date calculator can give you an estimated due date now! 

What should I do next?

If you don’t already have a midwife, you may be able to self-refer to your local maternity unit directly for your antenatal care. Visit your local hospital’s website to find out more.

Speak to your GP if you can’t self-refer or if you think your pregnancy may be high-risk. For example, if you have a long-term condition, had complications in a previous pregnancy or experienced a late miscarriage or stillbirth. Your GP will tell the midwifery team you are pregnant.

You will be given a date for your first appointment with a midwife. This should happen before you are 10 weeks pregnant. 

We know pregnancy can be an overwhelming time. We created our Healthy Pregnancy tool to try to take away some of this anxiety by giving you a personalised set of tips for your pregnancy. 

First Response is here for you on your pregnancy journey! Check out our learning center for expert guidance on trying to conceive, fertility and having a baby.

If you are wondering “how many weeks pregnant am I?” now’s the time to find out! Learn how far along you are in your pregnancy and estimated due date with the First Response pregnancy calculator. Starting with the first day of your last menstrual period it is easy to calculate when you conceived.

Find out your baby's due date so you can start planning key milestones.

When did your last period begin?

Please enter a valid date.

What is your average cycle length?

days

If my first day of my last period pregnancy calculator

Start with the first day of one period and count right up to the day before the first day of your next period. Count the first day of bleeding or spotting as day one. The average cycle length is 28 days, but can range anywhere from 20 to 45 days.

Your estimated due date is , that's away.

If my first day of my last period pregnancy calculator

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Do you count pregnancy from first day of last period?

Your weeks of pregnancy are dated from the first day of your last period. This means that in the first 2 weeks or so, you are not actually pregnant – your body is preparing for ovulation (releasing an egg from one of your ovaries) as usual.

How do you calculate pregnancy from last period?

Most pregnancies last around 40 weeks (or 38 weeks from conception), so typically the best way to estimate your due date is to count 40 weeks, or 280 days, from the first day of your last menstrual period (LMP). You could also subtract three months from the first day of your last period and add seven days.

When did I conceive based on first day of last period?

Conception usually occurs around 11-21 days after the first day of the last period of a woman who has a regular period. The estimation of conception date is based on this, but is rarely ever exact since it is difficult to know exactly when ovulation occurs.