Enter pregnancy details
Example data table
| Example input | Sample value | What it affects |
|---|---|---|
| Calculation method | Last menstrual period | Determines which formula starts the timeline. |
| LMP date | 2026-01-10 | Anchors gestational age and milestone offsets. |
| Average cycle length | 30 days | Adjusts due date by two extra days. |
| Date format | 07 Mar 2026 | Controls displayed milestone date style. |
Formula used
LMP method: Estimated due date = LMP + 280 days + (cycle length − 28).
Conception method: Estimated due date = conception date + 266 days.
Due date method: Estimated LMP = due date − 280 days.
IVF transfer method: Estimated due date = transfer date + (266 − embryo age in days).
Most milestone dates are then calculated by adding standard gestational offsets to the estimated LMP. For example, the second trimester starts at 14 weeks, the third trimester starts at 28 weeks, and the due date is 40 weeks.
Clinical dating can change after ultrasound review, irregular cycles, or fertility treatment notes. Use this calculator for planning and discussion support.
How to use this calculator
- Choose the dating method that best matches your available information.
- Enter the related date, and add cycle length when using LMP.
- Select your preferred date format for the results table.
- Press Calculate milestones to show the summary above the form.
- Review milestone windows for scans, testing, trimesters, and term ranges.
- Use the CSV or PDF buttons to save a portable copy.
Frequently asked questions
1. What date is most accurate for this calculator?
Use the earliest reliable medical dating information you have. A confirmed due date or fertility treatment date is often more precise than memory-based estimates.
2. Why does cycle length matter with LMP dating?
Longer or shorter cycles may shift ovulation timing. The calculator adjusts the due date relative to the standard 28-day cycle when you enter LMP.
3. Does this replace an ultrasound dating scan?
No. Ultrasound and clinician review can refine estimated gestational age, especially when cycles are irregular or the first known date is uncertain.
4. Can I use this after IVF treatment?
Yes. Choose the IVF transfer method and select the embryo age. The calculator converts transfer timing into an estimated due date and milestones.
5. Why are some milestones shown as windows?
Several appointments, scans, and tests are scheduled within recommended ranges rather than on a single exact day. Windows make planning more practical.
6. What does gestational age today mean?
It shows how many completed weeks and extra days have passed since the estimated pregnancy timeline start, usually based on LMP-style dating.
7. Can I download my results?
Yes. After calculation, you can export the milestone table as CSV for spreadsheets or as PDF for printing and sharing.
8. What if my clinician gives a different due date?
Use the clinician-confirmed due date method and recalculate. That keeps future milestones aligned with the medical schedule you are following.