Fitness & Health · Live
Your pregnancy timeline,
to the day.
A precise pregnancy calculator built on Naegele's rule and adjusted for your cycle length. Enter your last menstrual period or your conception date and see how many weeks you are, which trimester you're in, when every common milestone falls on the calendar, and the exact estimated due date.
Inputs
Calculate from
First day of your last menstrual period — the obstetric standard.
- LMP
- Fri, Mar 6, 2026
- Conception
- Fri, Mar 20, 2026
- Due date
- Fri, Dec 11, 2026
How far along
First trimester
Estimated due date: Fri, Dec 11, 2026 (Friday).
Right now
Where you are in the timeline
Heartbeat audible on doppler
An office doppler can usually pick up a fetal heartbeat from around 10 weeks. Range typically 110–160 bpm.
Fri, May 15, 2026
First-trimester screening (NT scan)
Ultrasound + blood test between 11 and 13⁺⁶ weeks screens for chromosomal conditions including Down syndrome.
Fri, May 29, 2026
Common milestones
Pregnancy timeline
| Week | Milestone | Date |
|---|---|---|
| 4w | First missed period | Fri, Apr 3, 2026 |
| 6w | Heartbeat detectable on ultrasound | Fri, Apr 17, 2026 |
| 9w | Embryo becomes a fetus | Fri, May 8, 2026 |
| 10w | Heartbeat audible on doppler | Fri, May 15, 2026 |
| 12w | First-trimester screening (NT scan) | Fri, May 29, 2026 |
| 13w | End of first trimester | Thu, Jun 11, 2026 |
| 18w | First fetal movements (quickening) | Fri, Jul 10, 2026 |
| 20w | Anatomy scan (anomaly scan) | Fri, Jul 24, 2026 |
| 24w | Viability threshold | Fri, Aug 21, 2026 |
| 27w | End of second trimester | Thu, Sep 17, 2026 |
| 28w | Glucose tolerance test | Fri, Sep 18, 2026 |
| 32w | Tdap vaccination | Fri, Oct 16, 2026 |
| 37w | Early term begins | Fri, Nov 20, 2026 |
| 39w | Full term | Fri, Dec 4, 2026 |
| 40w | Estimated due date | Fri, Dec 11, 2026 |
| 42w | Post-term | Fri, Dec 25, 2026 |
SEO field guide
Common pregnancy milestones
- Week 4
First missed period · positive home test
Most home pregnancy tests detect hCG by 4 weeks of gestational age, about a week after a missed period.
Trimester 1 - Week 6
Heartbeat detectable on ultrasound
A flickering heartbeat is usually visible on a transvaginal ultrasound at 6 weeks. The embryo is roughly the size of a lentil.
Trimester 1 - Week 9
Embryo becomes a fetus
All major organs are present in their basic form. Fingers, toes, and facial features begin to take shape.
Trimester 1 - Week 10
Heartbeat audible on Doppler
An office Doppler can usually pick up a fetal heartbeat from around 10 weeks. Range typically 110–160 bpm.
Trimester 1 - Week 12
First-trimester screening (NT scan)
Ultrasound + blood test between 11 and 13⁺⁶ weeks screens for chromosomal conditions including Down syndrome.
Trimester 1 - Week 14
Second trimester begins
The miscarriage risk drops sharply after week 12. Many parents share the news around this milestone.
Trimester 2 - Week 18
First fetal movements (quickening)
Most parents feel the first flutters between 16 and 22 weeks; second pregnancies often a week or two earlier.
Trimester 2 - Week 20
Anatomy scan
Detailed mid-pregnancy ultrasound between 18 and 22 weeks. Sex is usually visible if you choose to know.
Trimester 2 - Week 24
Viability threshold
From 24 weeks, a baby has a real chance of survival outside the womb with intensive neonatal care.
Trimester 2 - Week 28
Third trimester begins · glucose test
Routine screen for gestational diabetes between 24 and 28 weeks. Third-trimester appointments become more frequent.
Trimester 3 - Week 32
Tdap vaccination
Recommended between 27 and 36 weeks to give the newborn whooping-cough antibodies.
Trimester 3 - Week 37
Early term begins
Babies born from 37⁰ to 38⁶ weeks are 'early term' — full lungs, but still finishing up.
Trimester 3 - Week 39
Full term
Babies born from 39⁰ to 40⁶ weeks are 'full term', the lowest-risk window for elective delivery.
Trimester 3 - Week 40
Estimated due date
Only about 5% of babies arrive on the EDD itself. Most arrive between 38 and 42 weeks.
Trimester 3
Field guide
How a pregnancy calculator works.
Pregnancy is counted in gestational weeks from the first day of the last menstrual period (LMP), not from conception. That convention exists because the LMP is something you can usually pin down on a calendar, while ovulation is harder to know precisely. The trade-off is that your “weeks pregnant” number is roughly two weeks ahead of your “weeks since conception” number.
Naegele's rule (the EDD formula)
The estimated due date (EDD) is calculated using Naegele's rule, named after the German obstetrician Franz Karl Naegele who proposed it in 1812: take the first day of the LMP, add seven days, subtract three months, and add one year. The same result comes from a much cleaner formula: the EDD is exactly 280 days (40 weeks) after the LMP.
EDDcycle-adjusted = LMP + 280 + (cycleLength − 28) days
The cycle adjustment matters: Naegele's rule assumes a 28-day cycle with ovulation on day 14. A longer cycle shifts ovulation later and therefore the EDD later — by the same number of days.
The three trimesters
Pregnancy is divided into three trimesters, though the exact boundaries are a matter of convention:
- First trimester: weeks 1 through 13. Highest miscarriage risk, most fetal development. Symptoms peak around week 9.
- Second trimester: weeks 14 through 27. Often called the “honeymoon trimester”: early symptoms ease, the baby's sex becomes detectable, and quickening (first felt movements) usually occurs between weeks 16 and 22.
- Third trimester: weeks 28 through delivery. Routine appointments become more frequent. From 24 weeks onwards there is a real chance of survival if delivery happens early.
Term ranges (early-term, full-term, post-term)
The American College of Obstetricians and Gynecologists (ACOG) defines four delivery windows that matter for outcome research:
- Preterm: before 37 weeks (further divided into very-preterm and late-preterm).
- Early term: 37⁰ to 38⁶ weeks. Full lung development but slightly higher rates of respiratory issues than full term.
- Full term: 39⁰ to 40⁶ weeks. The lowest-risk window for elective delivery.
- Late term: 41⁰ to 41⁶ weeks. Most providers begin discussing induction here.
- Post-term: 42⁰ weeks and beyond. Induction is typically routine by this point.
LMP vs. ultrasound dating
Ultrasound dating in the first trimester (a crown-rump length, or CRL, measurement before 14 weeks) is generally more precise than LMP dating, because LMP recall is imperfect and ovulation timing varies. Standard practice is to use LMP unless the ultrasound estimate differs by more than 5–7 days in the first trimester (or 10–14 days in the second), at which point the ultrasound date supersedes the LMP date.
Conception date as the input
If you know your conception date directly, most often from IVF or careful fertility tracking — that's a cleaner anchor than LMP. Conception roughly equals ovulation, so the EDD is 266 days (38 weeks) after conception, or equivalently 40 weeks after the back-calculated LMP. This calculator uses both formulas under the hood and produces identical timelines either way.
LMP ≈ conception − 14 days
How accurate is the EDD?
Only about 5% of babies arrive on the EDD itself. About 50% arrive in the week either side of it, and roughly 90% between 38 and 42 weeks. The EDD is a statistical landmark, not a deadline.
Worked example
A pregnant person has an LMP of 1 January and a 28-day cycle.
- Conception ≈ 15 January (LMP + 14 days)
- EDD = 8 October (LMP + 280 days)
- First trimester ends ≈ 1 April (LMP + 13 weeks)
- Anatomy scan ≈ 21 May (LMP + 20 weeks)
- Viability ≈ 18 June (LMP + 24 weeks)
Shift to a 32-day cycle and every date above moves four days later. Shift to a 25-day cycle and every date moves three days earlier.
Disclaimer
This calculator is for educational use only and is not a substitute for professional prenatal care. Pregnancy timelines are highly individual, and a small percentage of pregnancies don't fit the standard pattern at all. Use this page as a planning landmark; let your obstetrician, midwife, or family physician be the authoritative source on every clinical question.