Due date calculator

Add the first day of your last period and we will work out your estimated due date, how far along you are and what the NHS usually offers next. Take it at your own pace.

Your estimated due date

Add a date

First day of your last period

Pick the first day of your last period and we will work out the rest.

What happens when

Your appointments and scans

This is what the NHS usually offers in England. Your midwife will give you your own dates, and they may be a little different. Some appointments are only for a first baby.

Now
Tell maternity servicesRefer yourself for NHS pregnancy care as soon as you know you are pregnant.
As soon as you can
8 to 12 weeks
First midwife appointmentOften called the booking appointment. It takes about an hour and you can ask anything.
11 to 14 weeks
Dating scanYour first ultrasound scan. It checks when your baby is due, with optional screening.
16 weeks
16 week appointmentA check in with your midwife about your screening results.
18 to 21 weeks
20 week scanA scan to check how your baby is developing.
25 weeks
25 week appointmentIf this is your first baby: your bump, blood pressure and a urine check.
28 weeks
28 week appointmentBlood tests, and the anti-D injection if you need it.
31 weeks
31 week appointmentIf this is your first baby: your 28 week results and a bump check.
34 weeks
34 week appointmentTime to talk about getting ready for labour and birth.
36 weeks
36 week appointmentChecking which way your baby is lying, and talking about feeding.
37 weeks
Full termFrom 37 weeks your baby is considered full term.
38 weeks
38 week appointmentTalking about your options if you go past 41 weeks.
40 weeks
Your due dateOnly a few babies arrive on the day itself, so try not to set your heart on it.
41 weeks
41 weeksIf you are still pregnant, your midwife will talk you through a membrane sweep and induction.

The working

How we work out your due date

We use Naegele's rule, which midwives have used for nearly 200 years. Pregnancy is counted from the first day of your last period, not from conception, so at conception you are already about 2 weeks pregnant.

Due date = first day of last period + 280 days + (your cycle length − 28 days)

If your cycle is usually 32 days, ovulation probably came a few days later than in a 28 day cycle, so we move the date 4 days later. Your dating scan at 11 to 14 weeks will give you a more accurate date, and that is the one your midwife will use.

Questions

Common questions

How accurate is a due date?

It is an estimate. Only a small number of babies arrive on the day itself, and most come in the couple of weeks either side. A pregnancy is full term from 37 weeks.

What if I do not know when my last period was?

That is very common. Your midwife will work out your dates from your dating scan instead, so there is nothing to worry about.

What if my periods are irregular?

The cycle length setting helps, but it is still a rough guide. Your dating scan is much more accurate when cycles vary.

When should I contact my midwife?

As soon as you know you are pregnant, you can refer yourself for NHS pregnancy care. After that, you can contact them any time you are worried. You do not have to wait for your next appointment.

Sources

Last checked 21 October 2026. Spotted something wrong? Tell us and we will fix it.

Your midwife is there for you

Call your midwife or maternity unit straight away if you have bleeding, a lot of pain, a bad headache or swelling, or your baby's movements slow down or change. Call NHS 111 if you cannot reach them, and 999 in an emergency. If this date brings up difficult feelings, Tommy's and the Miscarriage Association offer kind, free support.