Gestational Weeks on a Chosen Date
Check gestational age on a chosen date rather than only today. This calendar counts from the last menstrual period and must be distinguished from time since fertilisation or measured fetal development.
- Runs in your browser
- Nothing is uploaded
- No signup; device limits apply
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How to use this tool
Select the first day of LMP and the date to evaluate. Leaving the reference date blank uses today; enter it explicitly when comparing a past record or a future appointment.
Results and examples
Elapsed days are divided into weeks and remaining days, with LMP plus 280 days shown as due date. A negative days-to-due value does not establish whether birth has occurred.
Worked example
From 1 January 2026 to 5 February is five weeks zero days; the arithmetic due date is 8 October.
Limitations
- There is no ultrasound, embryo-transfer or irregular-cycle adjustment.
- The age number cannot determine urgency or a clinical test indication.
Fields
| Field | Guidance and constraints |
|---|---|
| Last menstrual period start (LMP) | Check the unit and format displayed beside this field. |
| Reference date (today if empty) | Check the unit and format displayed beside this field. |
Data handling
Processing stays in the current browser tab; the site does not upload tool input for the calculation itself.
Sources
Frequently asked questions
Can I view a past gestational age?
Yes. Choose the historical reference date.
What if clinical dating differs?
Check the dating that incorporates your clinician’s information.
Related tools
You do not need to start over. Continue with the tool that fits your next step.
