Calculate Pregnancy Days, Weeks, and Due Date
Use your last menstrual period (LMP) date to estimate how many days pregnant you are. You can also adjust cycle length for a more personalized due date estimate.
What is a pregnancy days calculator?
A pregnancy days calculator estimates gestational age in days and weeks + days using the first day of your last menstrual period (LMP). This is the same baseline method commonly used in prenatal care before ultrasound-based dating is available.
In practical terms, this tool can help you quickly answer questions like:
- How many days pregnant am I today?
- What week and day of pregnancy am I in?
- What is my estimated due date?
- How many days are left until due date?
How to use this pregnancy day calculator
1) Enter your LMP date
Choose the first day of your last menstrual period. This is the standard starting point for gestational age calculations.
2) Pick an “as of” date
By default, you can calculate as of today, but you can also use a future or past date to project timelines or review prior milestones.
3) Adjust cycle length (optional)
If your average cycle is longer or shorter than 28 days, adjust the cycle length field. This mostly affects the estimated due date and conception estimate, not the raw day count from LMP.
How pregnancy days are counted
LMP-based dating
Gestational age is typically counted from LMP, not from conception. That means in the first two weeks of pregnancy dating, fertilization usually has not occurred yet. This can feel odd at first, but it is the global clinical standard.
Estimated due date formula
A typical pregnancy is estimated as 280 days (40 weeks) from LMP in a 28-day cycle. If cycle length differs, due date can be adjusted by the difference:
- Adjusted gestation length = 280 + (cycle length − 28)
- Estimated due date = LMP + adjusted gestation length
Trimester ranges
- First trimester: 0 weeks to 13 weeks 6 days
- Second trimester: 14 weeks to 27 weeks 6 days
- Third trimester: 28 weeks onward
Understanding your result
After calculation, you will see a summary that includes:
- Pregnancy days completed as of your selected date
- Gestational age in weeks + days
- Estimated due date (cycle-adjusted if selected)
- Days remaining to due date (or overdue days)
- Approximate conception date
- Current trimester
Common questions
What if I do not remember my exact LMP?
If the date is uncertain, this calculator is still useful for rough planning. For medical dating, ultrasound and clinician assessment are more accurate.
Why might ultrasound dating be different?
Cycle irregularity, ovulation timing, implantation timing, and recall error can all shift calculated age. Early ultrasound can refine expected gestational age and estimated due date.
Can I use this for IVF pregnancy dating?
IVF pregnancies are often dated from embryo transfer and embryo age, which is more precise than LMP-based estimation. Use clinic-provided dates whenever available.
Pregnancy planning checklist by stage
Early weeks
- Start or continue prenatal vitamins with folic acid.
- Schedule first prenatal appointment.
- Review current medications with your healthcare provider.
Mid pregnancy
- Track anatomy scan and routine labs.
- Monitor nutrition, hydration, and movement recommendations.
- Plan leave, childcare, and home support strategy.
Late pregnancy
- Pack hospital bag and prepare key documents.
- Review labor signs and emergency contact plan.
- Complete newborn essentials and postpartum support planning.
Final note
This pregnancy days calculator is designed for educational and planning purposes. It can be a practical way to track milestones, but it does not replace professional prenatal care. Always follow your obstetrician, midwife, or healthcare team for medical guidance tailored to your pregnancy.