Obstetric Calculator: Due Date

Obstetric Calculator puts 23 evidence-based tools for pregnancy, labor and newborn care in one fast, offline app. It is built for obstetricians, midwives, residents, nurses and medical students who need a reliable answer at the bedside, in clinic or on the ultrasound unit.

Every calculator shows the publication it is based on, and the full references are one tap away. No guesswork and no hidden formulas.

PREGNANCY DATING
• Due date (EDD) from the last menstrual period, with Naegele's rule adjusted for cycle length
• EDD from an ultrasound report (scan date and reported gestational age)
• EDD from a known conception date
• Gestational age from the EDD on any chosen date
• EDD from quickening (rough estimate)
• A live pregnancy timeline from 0 to 42 weeks: a digital pregnancy wheel

ULTRASOUND
• Gestational age by crown-rump length (Robinson & Fleming, with INTERGROWTH-21st for comparison)
• Gestational age by fetal biometry: BPD, HC, AC and FL (Hadlock), alone or combined
• Fetal growth and Doppler: EFW centile (Hadlock 1991), umbilical artery PI centile (INTERGROWTH-21st) and cerebroplacental ratio
• Amniotic fluid: AFI and deepest vertical pocket, with oligohydramnios and polyhydramnios grading (SMFM, ACOG)

FETAL WEIGHT
• Estimated fetal weight by ultrasound with Hadlock formulas, SGA/AGA/LGA classification and centile
• Johnson–Toshach formula from fundal height
• Dare's formula (fundal height × abdominal girth)

PRENATAL CARE
• Pregnancy weight gain targets by pre-pregnancy BMI (IOM 2009), for singletons and twins
• Gestational diabetes OGTT interpretation: one-step 75 g (IADPSG / WHO 2013) and two-step 100 g (Carpenter–Coustan, NDDG), in mg/dL or mmol/L
• Preeclampsia risk factors and low-dose aspirin guidance (USPSTF 2021, ACOG)

LABOR AND DELIVERY
• Bishop score for cervical readiness before induction
• VBAC success at the first prenatal visit (MFMU 2021, without race or ethnicity)
• VBAC success at admission for delivery (MFMU model)
• Obstetric shock index for postpartum hemorrhage

NEWBORN
• Apgar score at 1 and 5 minutes (AAP and ACOG)
• New Ballard score for newborn gestational age

GYNECOLOGY
• Breast cancer risk with the Gail model (NCI BCRAT)
• Cervical screening schedule (WHO 2021)

BUILT FOR EVERYDAY CLINICAL WORK
• Results update as you type, with clear status labels and scales
• Copy a result in one tap to paste into notes or messages
• Search all calculators and reopen recently used ones
• Works completely offline, with no sign-up
• Light and dark mode

READY FOR YOUR COUNTRY
• 9 languages: English, Spanish, Portuguese (Brazil), French, Indonesian, Russian, Turkish, Vietnamese and Arabic
• Maternal weight and height in kg/cm or lb/ft-in
• Blood glucose in mg/dL or mmol/L, using the published thresholds for each unit
• Local date formats and clinical abbreviations (EDD, FPP, DPA, HPL and more)
• Ultrasound measurements always in metric units, as in clinical practice worldwide

IMPORTANT
Obstetric Calculator is a reference tool for healthcare professionals. This app is not a medical device and does not diagnose, treat, cure, or prevent any medical condition. Results support, but never replace, clinical judgment. Always consult a qualified healthcare professional for medical advice, diagnosis, or treatment.