Pregnancy Due Date
Estimate pregnancy due date (EDD) from last menstrual period using Naegele’s rule style math. Free MyCalcsWorld tool — educational, not medical advice.
Results
Estimated due date
- Days from today
- 19 days past estimate
You might also need
Educational estimates · not financial advice · free, no signup
Formula / how it works
Educational estimate only — confirm with a clinician.
Read the guide: How a Pregnancy Due Date Is Calculated
Detailed guide
What it is, how to use it, how to read the numbers, common mistakes, a worked example, formulas, and FAQs.
What this calculator is
Fitness numbers are starting points, not diagnoses. The Pregnancy Due Date on MyCalcsWorld uses published educational formulas so you can plan goals — then confirm with a clinician when it matters. What it does: Estimate due date from last menstrual period (Naegele’s rule, +280 days). Typical inputs: First day of last menstrual period. Demo defaults (first day of last menstrual period 2026-01-01) currently resolve to Estimated due date October 8, 2026 in the live panel — change any field to explore sensitivity. Who it helps: people setting fitness goals, coaches doing quick estimates, and anyone curious about BMI, calories, or training numbers — not a clinic visit.
When to use / who it helps
- Sketching an educational EDD from a known LMP date.
- Planning roughly around a 40-week timeline before a clinical visit.
- Comparing LMP-based dating with what your clinician later confirms on ultrasound.
- Jumping to pregnancy-week tracking once you have a dating anchor.
- Learning how Naegele-style math works — not replacing prenatal care.
How to use
Steps
- Enter the first day of your last menstrual period (LMP).
- Review estimated due date and gestational timing if shown.
- Confirm with your healthcare provider and ultrasound dating.
- Open the Pregnancy Due Date on MyCalcsWorld and skim the labeled fields before you type.
- Set First day of last menstrual period — demo default is 2026-01-01.
- Read the primary result first, then any secondary totals, chart, or table.
How to interpret results
- Only about 5% of births occur on the EDD — it is an estimate.
- Irregular cycles and IVF dating need clinician adjustment.
- Each result is driven only by the labeled inputs (First day of last menstrual period); anything not on the form (fees, holidays, clinical adjustments) is outside this estimate.
- Category labels (BMI bands, calorie targets) are population heuristics, not diagnoses.
- Small input changes (height rounding, activity level) can move calorie outputs by hundreds of kcal — treat ranges, not single points, as planning guides.
Common mistakes & gotchas
- Using last spotting instead of the first day of the last menstrual period.
- Trusting LMP dating with highly irregular cycles.
- Treating the EDD as exact — most births occur in a window around it.
- Skipping clinical confirmation for prenatal care decisions.
- Forgetting IVF and known-conception dating use different anchors.
Worked example
Worked example — Pregnancy Due Date (First day of last menstrual period = 2026-01-01)
- Open the Pregnancy Due Date (pregnancy due date) and note the starting defaults (first day of last menstrual period 2026-01-01).
- Use these labeled inputs (the form defaults): First day of last menstrual period = 2026-01-01.
- Read the live result panel. With those defaults, MyCalcsWorld currently reports: Estimated due date: October 8, 2026.
- Sanity-check against a hand calculation or spreadsheet using the formula notes for this Pregnancy Due Date.
- Optional: re-run with a second activity level or body-weight scenario to see a planning range.
Result: With defaults (first day of last menstrual period 2026-01-01), the Pregnancy Due Date shows: Estimated due date October 8, 2026.
To load the form's own demo values, tap Try example above the Calculate button.
How to calculate / formula
Educational estimate only — confirm with a clinician.
Frequently asked questions
What is Naegele’s rule?
A common educational estimate: EDD ≈ LMP + 280 days (about 40 weeks), with variants that add a year, subtract three months, and add seven days. Your clinician may refine this with ultrasound.
What if my cycles are irregular?
LMP-based dating is less reliable. Ultrasound dating and clinical judgment matter more — use this page only as a rough sketch.
Is this medical advice?
No. Seek licensed prenatal care for dating, screening, and health decisions.
Where do I track pregnancy week after dating?
Open the Pregnancy Week tool for week/day/trimester style educational tracking once you have an LMP or clinician dating anchor.
What does the Pregnancy Due Date on MyCalcsWorld actually compute?
Estimate due date from last menstrual period (Naegele’s rule, +280 days). You enter First day of last menstrual period, and the result panel updates in your browser.
What inputs does the Pregnancy Due Date need?
The Pregnancy Due Date asks for: First day of last menstrual period.
What results does the Pregnancy Due Date show?
The panel reports Estimated due date. Each figure is recalculated whenever you change an input, so you can compare scenarios side by side.
Which formula standard does this health tool follow?
We use widely published educational equations labeled in the formula notes. Individual labs and clinics may use alternate cutoffs or adjusted equations for athletes, pregnancy, or clinical populations.
For education and personal goal-setting only — not medical advice, diagnosis, or treatment. Talk to a qualified clinician about your health. Full disclaimer