Pregnancy calculator: how far along am I?
You’re 10 weeks 0 days pregnant
First trimester · due Monday, May 24, 2027 · 210 days to go. Pregnancy is counted from the first day of your last period, about two weeks before conception.
🔒 Calculated in your browser. Nothing you type is sent or stored. Estimates only: bodies vary.
A pregnancy calculator counts the days since the first day of your last period and divides by 7 to give your weeks and days. If you know your due date instead, it counts back 280 days to find that start date. So 84 days after your last period, you're 12 weeks 0 days pregnant. Enter either date above to see yours.
How the pregnancy calculator works
Pregnancy is counted in gestational weeks, starting from the first day of your last menstrual period (LMP). That's about two weeks before you actually conceived, which is why you're already "4 weeks pregnant" when your period is first late.
- Choose I know my last period or I know my due date.
- Enter the date. A due date from your dating scan gives the most accurate result.
- Read how many weeks and days pregnant you are today, your trimester, your due date and how many days are left.
The formula
Days pregnant = today − first day of last period. Weeks = days ÷ 7, with the remainder as extra days. If you start from a due date: last period = due date − 280 days, then the same sum. The due date shown is LMP + 280 days (40 weeks).
A worked example
Your last period started on August 3. On October 26 that's 84 days, so you're 12 weeks 0 days pregnant, near the end of the first trimester. Your due date is May 10, with 196 days to go.
Pregnancy weeks and trimesters
| Trimester | Weeks | What's often happening |
|---|---|---|
| First | 0 to 13 weeks 6 days | Missed period, tiredness, nausea, sore breasts. Dating scan offered around 10 to 14 weeks |
| Second | 14 weeks to 27 weeks 6 days | Energy often returns, the bump shows, first movements felt around 16 to 24 weeks. Anatomy scan around 18 to 22 weeks |
| Third | 28 weeks to birth | Growing tiredness, heartburn, more frequent checks. Full term is 39 to 40 weeks 6 days |
| Term | Gestational age (ACOG) |
|---|---|
| Preterm | Before 37 weeks 0 days |
| Early term | 37 weeks 0 days to 38 weeks 6 days |
| Full term | 39 weeks 0 days to 40 weeks 6 days |
| Late term | 41 weeks 0 days to 41 weeks 6 days |
| Postterm | 42 weeks 0 days and beyond |
Calculated in your browser, nothing stored. If your cycles are irregular or you're not sure of your last period, use the due date from your scan instead.
How accurate is a pregnancy weeks calculator?
The maths is exact, but it's only as good as the date you enter. The LMP method assumes a 28-day cycle with ovulation on day 14. With longer cycles you likely conceived later, so you may be a little less far along than the calculator says. That's why ACOG recommends confirming dates with a first-trimester ultrasound, and your provider may adjust your due date after it.
- Long or irregular cycles: use your scan date, or the due date calculator based on ovulation if you know when you ovulated.
- IVF: the transfer date is the most exact, see the IVF due date calculator.
- Not sure of anything yet: start with the due date calculator and update it after your scan.
Mood and energy in early pregnancy
Early pregnancy hormones (hCG, progesterone and estrogen) rise fast, and many people feel tired, tearful or on edge in the first trimester, a lot like a strong luteal phase. For many, energy and mood lift in the second trimester. Low mood that lasts most days for two weeks or more is worth mentioning to your midwife or doctor: depression in pregnancy is common and treatable.
Contact your midwife, doctor or maternity unit urgently for vaginal bleeding, severe tummy pain, a bad headache with vision changes or swelling, fluid leaking from the vagina, a fever, or (later in pregnancy) fewer or weaker baby movements.
Frequently asked questions
How far along am I if my last period was 8 weeks ago?
About 8 weeks pregnant. Pregnancy weeks are counted from the first day of your last period, not from conception.
How many weeks is a full pregnancy?
About 40 weeks (280 days) from the first day of your last period. Full term is 39 weeks 0 days to 40 weeks 6 days.
When does the second trimester start?
At 14 weeks 0 days. The third trimester starts at 28 weeks.
Why does my scan say a different week than my calculator?
Your last period date assumes ovulation on day 14. A first-trimester scan measures the baby directly, so it's usually more accurate and your provider may update your dates to match it.
Sources
- ACOG Committee Opinion 700: Methods for Estimating the Due Date
- ACOG Committee Opinion 579: Definition of Term Pregnancy
- NHS: Your pregnancy and baby guide
- NHS: 12-week scan
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
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