Different starting records
A last period, a recorded due date, dated pregnancy weeks, and an embryo-transfer record are not interchangeable inputs.
Pregnancy Metrics
Pregnancy date and week calculators
Start with the pregnancy record you already have. Pregnancy Metrics helps you choose between due-date, pregnancy-week, conception-estimate, and IVF transfer-date calculators without combining records that use different calendar rules.
Each tool shows the record used, the calendar arithmetic, the result’s limits, and the authoritative sources supporting that method.
Calculator entries are processed in your browser. No account is required, and Pregnancy Metrics does not store the dates you enter.
4 tools available now
Find the right calculator path
Match one record and one question before opening a calculator. This keeps last-period, due-date, dated-weeks, and embryo-transfer records in their appropriate calendar models.
Choose one option to see the matching path and its most important limit.
This chooser uses only the option selected on this page. It does not ask for or store a pregnancy date.
Available now
Four calculators, four different questions
Start with the question you need answered and the date information you already have. Each calculator explains its formula, assumptions, and limits alongside the result.
When is my due date?
Use the first day of your last period, a recorded ovulation date, or a documented fertilization date.
Record needed
Reliable last-period date, well-supported ovulation date, or documented fertilization date
How many weeks pregnant am I?
Use the due date in your pregnancy record or the first day of your last period.
Record needed
Current due date in the pregnancy record, or a reliable last-period date
About when might conception have happened?
Use a recorded due date, last period, or pregnancy weeks from a dated record.
Record needed
Recorded due date, reliable last period, or exact pregnancy weeks and days documented on a specific date
What is my IVF due date?
Use a documented Day-3 or Day-5 embryo transfer date.
Record needed
Actual or scheduled transfer date plus a documented Day-3 or Day-5 embryo age
Not sure which one fits the information you have? Use the record-first selection table.
Choose by the record you have
Do not choose a calculator only because its result sounds familiar. Start with the record you can verify, then choose the question you need answered.
| Record you have | Question you need answered | Start with | Important boundary |
|---|---|---|---|
| First day of a reliable last period | When is the estimated due date? | Pregnancy Due Date Calculator | The 280-day model assumes the last-period date is usable for dating |
| First day of a reliable last period | How many weeks and days pregnant? | Gestational Age Calculator | Pregnancy weeks use the obstetric calendar, not fetal age |
| Current due date in the pregnancy record | How many weeks pregnant on a date? | Gestational Age Calculator | Use the current recorded due date rather than averaging older dates |
| Current due date in the pregnancy record | About when might conception have occurred? | Conception Date Calculator | The output is an “around” calendar estimate, not an exact biological timestamp |
| Documented ovulation or fertilization date | When is the estimated due date? | Pregnancy Due Date Calculator | Use only a well-supported or documented date |
| Exact weeks and additional days recorded on a specific date | About when might conception have occurred? | Conception Date Calculator | Keep weeks, days, and record date from the same record |
| Day-3 or Day-5 embryo transfer record | What is the IVF due date? | IVF Due Date Calculator | Use the transfer date, not an earlier retrieval date |
| Only an intercourse date, positive test date, retrieval date, or an unknown embryo day | Which result should I calculate? | First obtain the appropriate pregnancy or transfer record | These dates cannot safely substitute for the supported inputs |
One record can support different questions. For example, a recorded due date can be used to show pregnancy weeks or to produce an approximate conception estimate, but those are different outputs with different limits.
Why these are four separate calculators
Different outputs
A due date, pregnancy age, conception estimate, and IVF due date answer different questions even when some dates are mathematically related.
Different certainty
A recorded clinical due date and an approximate conception date should not be presented with the same degree of certainty.
IVF uses a separate treatment record
Day-3 and Day-5 embryo-transfer dating uses the embryo age and transfer date rather than an ordinary menstrual-cycle estimate.
Keeping the tools separate reduces the risk of entering a familiar date into the wrong model or interpreting one type of result as another.
Two fixed examples show why the records must stay separate
Ordinary pregnancy-calendar example
- First day of last period: January 1, 2024
- Calendar conception estimate: Around January 15, 2024
- Pregnancy age on March 1, 2024: 8w4d
- Estimated due date: October 7, 2024
These values describe one fixed calendar timeline through several different questions. They do not prove the exact day of ovulation, fertilization, intercourse, or implantation.
IVF transfer-record example
- Day-5 blastocyst transfer: March 1, 2024
- Pregnancy-calendar age on transfer date: 2w5d
- Due-date rule: transfer date + 261 days
- Estimated IVF due date: November 17, 2024
This second example uses a documented embryo-transfer record. It must not be combined with the last-period dates from the first example.
The examples are educational calendar demonstrations. Use the dates documented for the actual pregnancy or treatment cycle.
What you can expect from every calculator
Your dates stay in your browser
The dates entered into a calculator are processed locally. No account is required, and the site does not save calculator inputs.
Every result names the record it used
Results show whether they were based on a last period, recorded due date, documented fertilization or ovulation date, or embryo transfer record.
Ordinary pregnancy and IVF dating stay separate
Last-period dating and embryo-transfer dating use different records and are not mixed together.
Calendar dates do not shift with time zones
Date-only calculations avoid accidental one-day browser timezone shifts. This improves technical consistency, not clinical certainty.
The calculation path is visible
Each calculator explains the calendar rule used for that result instead of presenting a date without showing how it was derived.
Limits are shown beside the result
Pages state what the calendar result can and cannot establish, including exact conception timing, viability, treatment decisions, and delivery timing.
How to interpret a result
The same calendar date can have different meanings depending on whether it is an input, an estimated output, or a date already established in a pregnancy record.
- A due date is an estimate, not a promised delivery day.
- Pregnancy weeks follow the record or date the user entered.
- A conception result is an “around” calendar estimate, not confirmation of fertilization or intercourse.
- IVF results depend on the correct embryo day and transfer date.
- A pregnancy record and early ultrasound can provide information a date-only calculator cannot evaluate.
When a calculator result differs from the current record used by the fertility clinic or prenatal care team, do not average the dates. Use the established record for care and ask the care team about the discrepancy.
How the site is maintained
Formula sources, assumptions, and update practices are documented in the methodology and editorial and methodology review. Pregnancy Metrics does not fabricate hospital, clinician, or society endorsements, and does not currently have external clinician certification.
Plain-language guides explain the same calendar rules without requiring you to enter a date.
Review the privacy notice and medical disclaimer, or email support@pregnancymetrics.com with a correction or accessibility concern.
What “reviewed” means on this site
Pregnancy Metrics reviews formula definitions, source claims, supported inputs, date arithmetic, edge cases, result wording, and tests. The site does not currently claim external clinician certification.
Where formula details live
Calculator pages explain the result-specific rule and sources. The Methodology documents shared constants, date-only arithmetic, boundaries, and update practices.
Current scope
Pregnancy Metrics currently provides four educational pregnancy date and week calculators. It does not provide diagnosis, pregnancy viability assessment, fetal wellbeing assessment, medication or treatment recommendations, emergency triage, or obstetric decisions.
The site’s current focus is intentionally narrow: pregnancy dating and pregnancy-calendar interpretation from supported records.
It does not attempt to become a general pregnancy symptom, diagnosis, treatment, medication, fertility-success, fetal-growth, or emergency-triage service.