Pregnancy calculator and estimated due date
Your pregnancy timeline
The usual NHS appointments, the work deadlines that are easy to miss, and when many parents start looking at the bigger baby items. Enter your dates above to see it with your own dates.
By week 10 · NHS care
Booking appointment with a midwife
Contact a midwife or GP as soon as you know you are pregnant. The booking appointment should ideally happen by 10 weeks.
Source: NHS: your antenatal appointments
Weeks 10 to 13 · NHS care
Dating scan
Usually offered between 10 and 14 weeks. It checks how far along you are and gives you a more accurate due date.
Source: NHS: 12-week scan
Weeks 16 to 31 · NHS care
Whooping cough vaccine
You can have it from 16 weeks, and it is usually given at around 20 weeks. Having it before 32 weeks gives your baby the best protection.
Weeks 18 to 20 · NHS care
20-week scan
Usually offered between 18 and 21 weeks. It looks at how your baby is developing.
Source: NHS: 20-week scan
Weeks 18 to 30 · Getting ready
A more comfortable pregnancy
As your bump grows, a pregnancy pillow can help you get comfortable on your side at night.
From week 20 · Work and pay
MATB1 certificate
Your midwife or GP can give you a MATB1 from about 20 weeks before your due date. Your employer uses it as proof of your due date for Statutory Maternity Pay.
Weeks 20 to 28 · Getting ready
Pushchair and car seat
Many parents look at these around now, while there is time to compare, try them in the shop and check the car seat fits your car.
By week 25 · Work and pay
Tell your employer
At least 15 weeks before your due date, tell your employer when the baby is due and when you want your maternity leave to start.
Weeks 24 to 32 · Getting ready
A safe place to sleep
The NHS advises a cot or Moses basket in the same room as you for at least the first 6 months, with a firm, flat mattress.
From week 28 · NHS care
RSV vaccine
Offered from 28 weeks of pregnancy. It helps protect your baby from RSV, a common cause of bronchiolitis.
Source: NHS: RSV vaccine
Weeks 28 to 34 · Getting ready
Bedtime basics
A baby sleeping bag in the right tog for the room keeps bedding simple and safe.
Weeks 28 to 34 · Getting ready
Feeding
Whether you plan to breastfeed, bottle feed or both, it helps to have the basics ready before the birth.
Weeks 30 to 36 · Getting ready
Bath time
A baby bath and a way to check the water temperature are all you need at first.
Weeks 32 to 36 · Getting ready
Hospital bag and changing
The NHS suggests having your hospital bag packed at least 3 weeks before your due date. Nappies, wipes and a changing bag are worth sorting at the same time.
From week 36 · Getting ready
Ready for the journey home
Fit the car seat before the birth and practise putting it in and out of the car, so the first journey home is calm.
This timeline is general information, not medical, legal or financial advice. Follow the advice of your midwife or GP, and check your rights with your employer or GOV.UK.
How does the pregnancy calculator work?
Pregnancy is counted from the first day of your last period, not from the day you conceived. This date is often called your LMP (last menstrual period). Conception usually happens around 2 weeks later, but the exact day is rarely known, so midwives and doctors use the first day of your last period as the starting point.
How do we calculate your due date?
We add 280 days (40 weeks) to the first day of your last period. This is known as Naegele's rule. If your cycle is usually shorter or longer than 28 days, we move the due date earlier or later by the difference, and adjust the number of weeks pregnant in the same way.
The result is an estimate. You'll often see weeks of pregnancy written as weeks plus days, so 20+3 means 20 weeks and 3 days. The NHS also has its own due date calculator.
How long does a pregnancy last?
Pregnancy normally lasts from 37 to 42 weeks from the first day of your last period, so most babies are not born on their due date itself. A baby born before 37 weeks is premature.
If you do not go into labour naturally by 41 weeks, you'll be offered induction of labour, and a membrane sweep is usually offered before that, after 39 weeks. It's your choice whether to be induced. If your pregnancy lasts longer than 42 weeks and you decide not to be induced, you should be offered increased monitoring to check your baby's wellbeing.
What if I don't know the date of my last period?
If you are not sure of the date, or your periods are irregular, the calculator may not give an accurate result. In England, you'll be offered a dating scan at around 10 to 14 weeks of pregnancy. It is used to work out how many weeks pregnant you are and your due date, so it can replace the date given by this calculator.
Why is pregnancy counted in weeks rather than months?
Your baby develops quickly, and antenatal appointments, scans and screening tests are all timed by week of pregnancy. Weeks are also more precise than months, which have different numbers of days.
How many months pregnant am I?
Months are only a rough guide, but the table below shows approximately how the weeks of pregnancy match the three trimesters and nine months.
| Trimester | Weeks | Months |
|---|---|---|
| 1st | 1-4 | one |
| 5-8 | two | |
| 9-13 | three | |
| 2nd | 14-17 | four |
| 18-22 | five | |
| 23-27 | six | |
| 3rd | 28-31 | seven |
| 32-35 | eight | |
| 36-40 | nine |