Pregnancy · Timing
Pregnancy Week Calculator
Calculate weeks + days from LMP. Trimesters, key milestones (scans, screens, GTT, anti-D, GBS), antenatal schedule. NICE NG201.
Last reviewed June 2, 2026
Current gestational age
How many weeks pregnant am I?
What you know
Pick a method and enter the date to see your current pregnancy week.
How weeks are counted
From first day of LMP. ‘Weeks + days’ format (e.g. 22+3). 40 weeks = full term EDD. Dating scan (11-13+6 wks) most accurate.
Trimesters
- T1: weeks 0-12.
- T2: weeks 13-27.
- T3: weeks 28-birth.
Key milestones
- 6-7 wk: heartbeat on transvaginal scan.
- 8-11 wk: nausea peak.
- 11-13+6 wk: NIPT, combined screen, dating.
- 16-20 wk: first movements (quickening).
- 20 wk: anomaly scan + sex.
- 24 wk: viability.
- 28 wk: GTT, anti-D.
- 36 wk: GBS swab, presentation.
- 37 wk: term.
- 41 wk: sweep / induction discussion.
First trimester (0-12 wk)
- Nausea peaks 8-11 wk.
- Fatigue.
- Breast tenderness.
- Frequent urination.
- Mood changes.
- Highest miscarriage risk <13 wk.
Second trimester (13-27 wk)
- Nausea reduces.
- Energy returns.
- Bump visible.
- Quickening 16-20 wk.
- 20-wk anomaly scan.
- Round ligament pain emerging.
Third trimester (28-birth)
- Braxton Hicks.
- Shortness of breath.
- Sleep disturbance.
- Back / hip / pelvic pain (relaxin, SPD).
- Oedema.
- GTT 28 wk; anti-D; GBS 35-37 wk.
- Birth plan + perineal prep.
Term categories
- Preterm: <37 wk.
- Early term: 37-38+6.
- Full term: 39-40+6.
- Late term: 41-41+6.
- Post-term: ≥42+0.
Movement patterns
- 16-20 wk: first felt.
- 20-25 wk: stronger.
- 25-32 wk: pattern emerges.
- 28-40 wk: know your baby’s normal pattern.
REDUCED movements: contact maternity URGENTLY, same day, any time. Don’t wait, don’t rely on sugary food / drinks.
Antenatal appointments (UK)
- Booking 8-10 wk.
- 12 wk: combined screen + dating.
- 16 wk: review.
- 18-22 wk: anomaly scan.
- 25 wk (1st-time).
- 28 wk: bloods + anti-D + GTT.
- 31 wk (1st-time).
- 34 wk: bloods.
- 36 wk: presentation + birth plan + GBS.
- 38, 40, 41 wk.
Different scenarios
Scenario 1: 12-week dating scan adjusts EDD by 6 days
Use scan-based EDD going forward.
Scenario 2: 25 weeks, no movements felt today
Pattern early in this gestation. Maternity contact for reassurance if any concern.
Scenario 3: 30 weeks, reduced movements vs usual
Maternity URGENTLY same day. CTG + scan.
Scenario 4: 36 weeks, baby breech
Discuss ECV (external cephalic version) or planned C-section.
Scenario 5: 41+3 weeks, induction declined
Expectant management with twice-weekly CTG + scans. Inform consent.
Care guidance
- Track weeks + appointments.
- Know normal movement pattern.
- Reduced movement = urgent.
- Attend all scans.
- Folic acid + vitamin D throughout.
- Hydration + nutrition + sleep.
Sources
- NICE NG201. Antenatal care.
- NICE NG207. Inducing labour.
- RCOG GTG. Reduced fetal movements.
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Frequently asked questions
How is pregnancy week calculated?
Counts from FIRST DAY of last menstrual period (LMP). 'Weeks + days' format (e.g. 22+3 = 22 weeks 3 days). 40 WEEKS = full term EDD. Most accurate if dating ultrasound (CRL at 11-13+6 weeks) confirms. CYCLE-IRREGULAR or DATES UNCERTAIN: ultrasound adjusts. IVF: calculated from embryo transfer date.
Trimesters — where do they split?
(1) TRIMESTER 1: weeks 0-12 (or 0-13 by some conventions). (2) TRIMESTER 2: weeks 13-27. (3) TRIMESTER 3: weeks 28-birth. NHS sometimes uses 12-week / 28-week cutoffs. Each trimester has distinct development + risks.
Key gestational milestones?
(1) 6-7 WEEKS: heartbeat visible on transvaginal ultrasound. (2) 8-10 WEEKS: nausea peak. (3) 10-13 WEEKS: NIPT, combined screen, NT scan. (4) 16-20 WEEKS: first movements (quickening). (5) 20 WEEKS: anomaly scan, fetal sex. (6) 24 WEEKS: viability legal limit UK. (7) 28 WEEKS: anti-D, glucose tolerance test. (8) 36 WEEKS: GBS swab; presentation; birth plan. (9) 37 WEEKS: term.
When do I look pregnant?
FIRST PREGNANCY: bump visible 16-22 weeks usually. SUBSEQUENT pregnancies: showing earlier (12-16 weeks). MULTIPLE pregnancies: much earlier + larger. VARIABLE based on body shape, BMI, fundal position. SLIM, FIT bodies sometimes show later; petite bodies sometimes earlier. NORMAL variation wide.
First trimester — what to expect?
Weeks 0-12: NAUSEA peaks 8-11 weeks (some develop hyperemesis — severe; needs treatment); FATIGUE; BREAST tenderness; FREQUENT URINATION (uterus pressure + hormonal); FOOD AVERSIONS / cravings; MOOD changes; LIGHT spotting (some); MISCARRIAGE most common <13 weeks. SCANS: 6-7 wk early viability optional; 11-13+6 wk combined + dating.
Second trimester — what to expect?
Weeks 13-27: 'GLOW' period — nausea reduced; ENERGY return; BUMP visible; FETAL MOVEMENTS felt (quickening 16-20 wks); 20-WK ANOMALY scan + sex; BACK + PELVIC pain emerging; ROUND LIGAMENT pain; HEARTBURN; SKIN changes (melasma, linea nigra); BABY SIZE 13 cm at 16 wk → 35 cm at 27 wk.
Third trimester — what to expect?
Weeks 28-birth: BIG bump + braxton hicks (practice contractions); SHORTNESS of breath; SLEEP DISTURBANCE; BACK PAIN; HIP PAIN (relaxin); PELVIC PAIN (SPD); INSOMNIA; FATIGUE return; OEDEMA (swelling); GTT 28 wks (gestational diabetes); ANTI-D if Rh-negative; GBS swab 35-37 wks; BIRTH PLAN; PERINEAL prep.
When is term?
(1) PRETERM: <37 weeks. (2) EARLY TERM: 37 - 38+6 weeks. (3) FULL TERM: 39 - 40+6 weeks. (4) LATE TERM: 41 - 41+6 weeks. (5) POST-TERM: ≥42+0 weeks (induction usually before this per NICE NG207). EDD = 40 wks but only ~5% on date.
Antenatal appointments by week (UK)?
(1) BOOKING: 8-10 weeks; bloods, history, plans. (2) 12 WEEKS: combined screen + dating scan + NT. (3) 16 WEEKS: BP, MSU, midwife review. (4) 18-22 WEEKS: 20-week anomaly scan. (5) 25 WEEKS (first-time mums): midwife. (6) 28 WEEKS: bloods, anti-D, GTT. (7) 31 WEEKS (first-time): midwife. (8) 34 WEEKS: bloods. (9) 36 WEEKS: presentation, birth plan, GBS. (10) 38 WEEKS: late routine. (11) 40 WEEKS: term. (12) 41 WEEKS: sweep / induction discussion. NICE NG201.
How accurate is dating scan?
(1) FIRST-TRIMESTER CRL (11-13+6 wks): MOST ACCURATE (±5 days). (2) LATER first trimester / early 2nd: ±7-10 days. (3) MIDDLE 2nd trimester: ±10-14 days. (4) THIRD trimester: ±21 days (unreliable). EDD usually fixed by 12-week scan unless major discrepancy. NICE NG201.
Movement patterns by week
(1) 16-20 WEEKS: first felt by mum (multiparous: earlier; primigravida: later); fluttering 'quickening'. (2) 20-25 WEEKS: stronger; partner can feel. (3) 25-32 WEEKS: pattern emerges; sleep + wake cycles. (4) 28-40 WEEKS: monitor regular movements — reduced movements = urgent assessment same day. NHS encourages knowing your baby’s normal pattern, not 'kicks per hour'.
Reduced fetal movements — what to do?
URGENT contact maternity if you notice REDUCED, ABSENT or DIFFERENT movement pattern. DON’T wait. DON’T rely on sugary food / drinks (myth). Call maternity for assessment (CTG, scan). Better safe — reduced movements can signal placental issues.
How does this relate to other calculators on BumpBites?
Companion: /calculators/due-date; /calculators/due-date-countdown; /calculators/ivf-due-date; /calculators/baby-size-by-week; /calculators/movement-tracker; /calculators/fetal-weight; /calculators/membrane-sweep.