Calculate Your Estimated Due Date
Estimated Due Date:
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👶 Overview: What This Pregnancy Due Date Calculator Does
This tool helps expecting parents, midwives, and doctors estimate a baby’s expected arrival date. You can calculate your due date using:
- 🩸 Your Last Menstrual Period (LMP)
- ❤️ Your Date of Conception
- 📅 An optional Cycle Length Adjustment (default: 28 days)
The calculator follows standard obstetric formulas and can help track pregnancy progress, plan prenatal appointments, and set up maternity planning.
📐 Formulas & Medical Methodology
The two most widely used due date formulas are:
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LMP Method:
\( \text{Due Date} = \text{LMP Date} + 280 \text{ days} \)
➕ If your cycle differs from 28 days, adjust by adding:
\( (\text{Your Cycle Length} - 28) \) days -
Conception Method:
\( \text{Due Date} = \text{Conception Date} + 266 \text{ days} \)
These methods are based on the assumption of a 40-week (280-day) gestation from the start of your last period or a 38-week (266-day) count from ovulation/conception.
🧮 Example Calculations
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LMP Method:
LMP = January 1, 2025
\( \text{Due Date} = \text{Jan 1, 2025} + 280 \text{ days} = \text{October 8, 2025} \) -
Conception Method:
Conception = January 15, 2025
\( \text{Due Date} = \text{Jan 15, 2025} + 266 \text{ days} = \text{October 8, 2025} \) -
Irregular Cycle:
LMP = March 5, 2025, Cycle = 32 days
Adjustment = \( +4 \text{ days} \)
Due Date = March 5 + 284 = December 14, 2025
🍼 Common Use Cases
- 🎯 Planning prenatal appointments and maternity leave
- 🧘 Preparing for birth classes or hospital registration
- 📆 Comparing LMP and conception-based due dates
- 🔁 Adjusting calculations for irregular menstrual cycles
- 🤰 Tracking week-by-week pregnancy milestones
Whether you're early in pregnancy or confirming your timeline, this tool makes it simple and reliable.
❓ Frequently Asked Questions (FAQ)
How is my due date calculated from LMP?
The calculator adds 280 days (40 weeks) to the first day of your last menstrual period (LMP), which assumes a 28-day cycle and ovulation around day 14.
Why are there two methods—LMP and Conception?
LMP is often more accessible for patients, while conception is more accurate if ovulation is precisely known (e.g., via IVF or ovulation tracking).
How does cycle length affect the result?
If your cycle is longer than 28 days, ovulation likely occurs later—so we add extra days. For shorter cycles, we subtract. Example: a 32-day cycle adds 4 days to the due date.
Is this due date exact?
No—this is an estimate. Only about 4% of babies are born exactly on their due date. It's a guideline used for tracking progress.
How many weeks pregnant am I?
Count from your LMP. For example, if your LMP was 10 weeks ago, you're around 10 weeks pregnant. The tool often shows both due date and weeks elapsed.
Can this be used for IVF pregnancies?
For IVF, use the embryo transfer date and consult your fertility provider—due dates are calculated slightly differently.
How often should I recalculate?
Only once—your due date doesn’t change unless your doctor adjusts it based on ultrasound measurements.