Life & Health Β· π Global
Pregnancy Week Calculator
Pregnancy week and due date calculator with LMP, Ovulation, and Ultrasound modes. Weekly fetal info and ICS prenatal visit calendar.
About this tool
Pregnancy Week Calculator uses three input modes β LMP (last menstrual period), ovulation date, or ultrasound CRL (crown-rump length) β to compute the current gestational age (W+D) and EDD instantly. Base: Naegeleβs rule (LMP + 280 days). LMP mode applies cycle-length correction (21β45 days); CRL uses Robinson-Fleming (GA = 8.052 Γ βCRL + 23.73). Includes week-by-week fetal size/development (1β40 weeks, Hadlock + Papageorghiou standards), trimester checklists (prenatal tests, vaccines, contraindications), ICS prenatal-visit calendar, OG share card, and bilingual KO/EN UI. Runs entirely in the browser; LMP/CRL never leave the device.
Use cases
Scenario 1
EDD after first positive test
A newly pregnant person uses LMP mode (28-day default) to get EDD and current week, then plans the first OB visit.
Scenario 2
Irregular-cycle correction
For a 35-day cycle, the tool corrects EDD ~7 days later than the default LMP+280 baseline.
Scenario 3
Ultrasound CRL re-dating
Enter the 8β12-week CRL to compare with the LMP estimate; the tool flags ACOGβs 5-day gap rule (LMP < 9 weeks) for re-dating.
Scenario 4
IVF transfer-date calc
IVF patients enter conception derived from transfer date in ovulation mode for Β±2β3-day EDD precision.
Scenario 5
Trimester ICS calendar
Pull the trimester prenatal-test / vaccine / contraindication checklist as an ICS file and auto-load every appointment to the calendar.
Features
- 3 input modes: LMP / ovulation / ultrasound CRL
- Cycle-length 21β45-day correction + Robinson-Fleming CRL
- Week-by-week fetal size/development (1β40 weeks, Hadlock + INTERGROWTH-21st)
- Trimester checklists (tests, vaccines, contraindications)
- ICS prenatal-visit calendar export
- OG share card (for partner / family)
- In-browser only β LMP/CRL never sent to a server
Frequently asked
- Q. LMP vs ultrasound EDD β which wins?
- A. In the first trimester (β€13w6d), ultrasound CRL is more accurate. ACOG re-dates to ultrasound if LMP/US disagree by β₯5 days at <9 weeks or β₯7 days at 9β15 weeks.
- Q. Does LMP work for irregular cycles?
- A. Naegele assumes 28 days β a 35-day cycle skews EDD 7 days early. The tool corrects via the 21β45-day cycle input.
- Q. I know my ovulation date β which mode?
- A. Use "ovulation mode" (conception + 266 days = EDD). It ignores cycle length; for IVF, derive conception from transfer date.
- Q. Which fetal-size standard is used?
- A. A blend of INTERGROWTH-21st (Papageorghiou) and Hadlock. CRL to 12 weeks; BPD/FL/AC after 14. Anomalies >Β±2 weeks warrant a detailed scan.
- Q. Does this replace medical advice?
- A. No β it is a reference calculator. All medical judgment in pregnancy must come from your OB-GYN.
Sources / references
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How we run it / disclaimer
This tool is advisory and does not constitute legal, tax, medical, or financial advice. All calculations and document generation run in your browser; inputs are never sent to a server. Ads follow Google AdSense policy and are kept separate from tool accuracy.