Pregnancy
Pregnancy Due Date Calculator
Work out your due date from your last period, a conception date, an IVF transfer or an ultrasound measurement — then see every date that matters for the next nine months on one timeline.
How it works
Four ways to date a pregnancy
A pregnancy is counted from the first day of your last period, not from conception — which is why you are already "four weeks pregnant" before anything has happened. Each method below converts back to that same starting point, and the tool does the rest.
| Method | The rule |
|---|---|
| Last period (LMP) | Due date = first day of your last period + 280 days (40 weeks). This assumes a 28-day cycle with ovulation on day 14, so if your cycles are longer or shorter the result is adjusted by the difference. |
| Conception date | Due date = conception + 266 days (38 weeks). The two-week gap is because pregnancy is counted from your period, roughly a fortnight before you conceived. |
| IVF transfer | A day 5 transfer dates the pregnancy at + 261 days; a day 3 transfer at + 263 days. This is the most precise method available, because the exact age of the embryo is known. |
| Ultrasound | The scan gives a measurement of how far along you were on that date, which converts back to a starting point and then + 280 days. First-trimester scans are accurate to within a few days, which is why providers often revise a due date after one. |
Not sure which to pick? Use the last period unless you have had a dating scan — then use the scan, because it supersedes the others.
This is a calculator, not medical advice. It does arithmetic on the dates you enter and knows nothing about your pregnancy. A due date is an estimate, not an appointment.
Everything on this page — the dating methods, the milestone dates, the week-by-week notes — is general information. It is not clinical guidance and it is not a substitute for your own care. Talk to your midwife, doctor or provider about anything to do with your pregnancy or your baby's health.
This is the default method, and it is what most providers use first. It assumes ovulation on day 14 of a 28-day cycle — if your cycles are longer or shorter, the length above adjusts the result.
Only useful if you know the date — from tracking ovulation, or from a single possible date. Conception is dated at 266 days before the due date, because a pregnancy is counted from the last period, roughly two weeks before conception.
Dating from an IVF transfer is the most precise method there is, because the exact age of the embryo is known. Day 5 transfer + 261 days. Day 3 transfer + 263 days. Most general calculators ignore IVF entirely and give you a date that is days out.
A first-trimester ultrasound is the most accurate dating method available, which is why providers often revise your due date after one. Enter what the sonographer measured, not what you thought you were.
Pick a method and enter a date
Your due date appears here
Not sure which to use? The last menstrual period is the default, but a first-trimester ultrasound is the most accurate if you have had one.
Every date that matters, in order
A due date is one number. These are the rest of them — the appointments and markers that actually structure a pregnancy. Each one is dated from your input above.
Where you are, week by week
Your baby, week by week
What is happening at each week of pregnancy, from the first weeks through to full term.
What the size comparison means: the fruit is a way of picturing something you cannot see yet — it is not an ingredient list. Saying your baby is "the size of a blueberry" means it is roughly that length at that week. The bars below fill as the weeks pass, so you can see how quickly the comparisons grow.
First trimesterWeeks 4–13
Week 4
Poppy Seed
Your baby is implanting into the uterine wall. The embryo has two tiny layers of cells.
Week 5
Sesame Seed
The heart is beginning to form and will soon start beating.
Week 6
Sweet Pea
The neural tube is closing. The heart is beating about 110 times per minute.
Week 7
Blueberry
The brain is developing rapidly. Arm and leg buds are growing.
Week 8
Raspberry
Tiny fingers and toes are forming. Your baby is constantly moving.
Week 9
Cherry
All essential organs are in place. Muscles are beginning to form.
Week 10
Strawberry
Vital organs are beginning to function. Tiny tooth buds are forming.
Week 11
Fig
Your baby can open and close their fists. Tooth buds are appearing.
Week 12
Lime
Reflexes are kicking in. Your baby can make sucking motions.
Week 13
Lemon
Fingerprints are forming. Vocal cords are developing.
Second trimesterWeeks 14–27
Week 14
Peach
Your baby can make facial expressions. The body is growing faster than the head.
Week 15
Apple
Your baby can sense light through closed eyelids.
Week 16
Avocado
The skeleton is hardening from cartilage to bone.
Week 17
Pear
Fat storage is beginning. Sweat glands are developing.
Week 18
Bell Pepper
Your baby can hear sounds! You may feel the first kicks.
Week 19
Mango
A protective coating called vernix is forming on the skin.
Week 20
Banana
You are halfway there! This is typically when the anatomy scan happens.
Week 21
Carrot
Eyebrows and eyelids are fully formed.
Week 22
Papaya
The sense of touch is well developed. Lips are forming.
Week 23
Grapefruit
Lungs are beginning to produce surfactant for breathing.
Week 24
Corn
Lungs are beginning to produce surfactant, which helps them work. The inner ear is fully developed.
Week 25
Cauliflower
Your baby is gaining baby fat and the skin is becoming less translucent.
Week 26
Lettuce
Eyes are beginning to open. Your baby can respond to sounds.
Week 27
Cabbage
Your baby can recognize your voice and has regular sleep cycles.
Third trimesterWeeks 28–40
Week 28
Eggplant
Third trimester begins! Your baby can blink and is dreaming.
Week 29
Butternut Squash
The brain is developing rapidly. Muscles are getting stronger.
Week 30
Coconut
Your baby weighs about 3 pounds and is gaining weight steadily.
Week 31
Pineapple
All five senses are working. Brain connections are forming rapidly.
Week 32
Squash
Your baby is practicing breathing movements. Toenails are growing.
Week 33
Celery
Bones are hardening. The immune system is developing.
Week 34
Cantaloupe
The central nervous system and lungs are maturing.
Week 35
Honeydew Melon
Kidneys are fully developed. Liver can process waste.
Week 36
Romaine Lettuce
Gaining about an ounce per day. Baby may drop into the pelvis.
Week 37
Swiss Chard
Considered early term! Lungs are mature and ready for breathing.
Week 38
Leek
Brain and lungs continue maturing. Your baby has a firm grasp.
Week 39
Watermelon
Full term! Your baby weighs around 7+ pounds and is ready to arrive.
Week 40
Pumpkin
Due date! Average weight is 7.5 lbs (3.4 kg) and 20 inches (51 cm) long.
Reality check
How accurate is a due date, really?
Less precise than the word "date" suggests. It is an estimate, and a due date is best read as the middle of a window rather than an appointment.
| Question | What is actually true |
|---|---|
| Do babies arrive on their due date? | Only a small minority do. It is a midpoint, not a deadline — which is exactly why providers talk about a window rather than a day. |
| How wide is the window? | Wider than most people expect. Ask your own midwife or doctor what they consider normal for your pregnancy, because it differs with whether this is your first baby and with any complications. |
| Can my due date change? | Yes. A first-trimester ultrasound often revises it, and providers usually adopt the scan date over the LMP calculation when the two disagree by more than a few days. |
| What if I have no idea when my last period was? | Use the ultrasound method if you have had a scan. If not, an early scan is the usual way to establish dating — ask your provider. |
This tool does arithmetic. It does not know anything about your pregnancy, and it is not medical advice. Your provider's dating is the one that counts.
Questions
Due date questions, answered
How is a due date calculated?
The standard method is the first day of your last menstrual period plus 280 days, or 40 weeks. That assumes a 28-day cycle with ovulation on day 14; if your cycle is longer or shorter, the calculator adjusts for it. Conception dating uses 266 days instead, IVF transfer dating uses 261 days for a day-5 transfer or 263 for a day-3 transfer, and ultrasound dating converts the scan measurement back to a starting point and adds 280 days.
Can I calculate a due date from an IVF transfer?
Yes, and it is the most accurate method there is. For a day-5 blastocyst transfer, the due date is 261 days after the transfer. For a day-3 transfer, it is 263 days. Because the exact age of the embryo is known at transfer, there is no guesswork about when ovulation happened.
How many weeks pregnant am I?
Enter your dates in the calculator above and it shows your current week and day, along with how many days remain. Pregnancy is counted from the first day of your last period, so you are considered two weeks pregnant at conception and four weeks pregnant around the time of a missed period.
What if I do not know the date of my last period?
Use a different method. If you know roughly when you conceived, use the conception option. If you have had an ultrasound, use that — a first-trimester scan is the most accurate way to date a pregnancy, and it is what your provider will rely on. If neither applies, an early scan is the usual route.
Why is my due date different from another calculator?
Because of the cycle length assumption. Most calculators silently assume a 28-day cycle, so if yours is 32 days your due date is genuinely about four days later. Set your actual cycle length in the last-period option and the two numbers should agree.
How accurate are due dates?
They are estimates, not appointments. Only a small proportion of babies arrive on the calculated date, which is why providers treat it as the centre of a window rather than a fixed day. A first-trimester ultrasound gives the most reliable dating and often revises the LMP estimate.
By stage
What people tend to buy, and when
Nothing here is medical and nothing here is urgent. It is the shopping that naturally goes with each stage — comfort, clothing and keepsakes. Your due date does not change what you need, it just tells you how long you have.
| Stage | Commonly bought |
|---|---|
| First trimester Weeks 4–13 |
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| Second trimester Weeks 14–27 |
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| Third trimester Weeks 28–40 |
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If you are building a registry rather than shopping for yourself, the registry checklist covers all 118 items by stage and priority — and you can copy the finished list straight into Amazon, Babylist or Target.
Next
Once the dates are settled
Knowing the date is step one. These are the tools that answer the questions that come next.