Pregnancy Calculator
Calculate the conventional estimated due date of 280 days from the first day of the last menstrual period, with simple planning milestones.
Use the Pregnancy Calculator
Calculate the conventional estimated due date of 280 days from the first day of the last menstrual period, with simple planning milestones.
Calculation, text generation and supported file processing happen locally in your browser; this batch does not require a new external processing service.
Health information only. This page performs the stated arithmetic/estimate and is not a diagnosis, treatment plan, medical clearance, fertility guarantee or substitute for a qualified health professional. Seek urgent medical care for urgent symptoms or concerning readings.
Reference used for this implementation: ACOG estimated due date guidance: https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date
How to use it
Start with the realistic worked example, replace it with your own verified values or files, inspect the result, and check the stated assumptions and limitations before using the output.
How the Pregnancy Calculator works
Calculate the conventional estimated due date of 280 days from the first day of the last menstrual period, with simple planning milestones. ToolLott presents this as a health screening/planning estimate, not a diagnosis, and anchors the method to the authoritative reference(s) listed below plus the passed Build 0232 QA fixture.
Calculation breakdown
ToolLott will explain the current inputs and displayed result here.
LMP-based estimated due date
The production method for Pregnancy Calculator is: Estimated due date = first day of LMP + 280 days (40 weeks), subject to clinical dating conventions. The calculation keeps the entered values visible and the live explanation changes with the current result so users can see exactly what was estimated.
Estimated due date = first day of LMP + 280 days (40 weeks), subject to clinical dating conventionsToolLott evaluates the documented relationship with the entered values before display formatting.
| Symbol / input | Meaning | Unit |
|---|---|---|
lmp | First day of last menstrual period | user input |
Step-by-step method
- Validate the required age/body/calendar/reading inputs and their units.
- Apply the documented lmp-based estimated due date relationship to the entered values.
- Interpret the output as an estimate or tracking summary and use appropriate clinical guidance for diagnosis, treatment, pregnancy dating or individual health decisions.
Worked example
Mia, a person tracking general wellness information, has a recorded last-menstrual-period date of 1 July 2026 and wants the conventional estimated due-date arithmetic for appointment planning before clinical dating is confirmed.
Example inputs
- First day of last menstrual period: 2026-07-01
Calculation / processing
Use the verified QA fixture: First day of last menstrual period: 2026-07-01.Apply the production lmp-based estimated due date workflow exactly as described on this page.The production QA fixture reports: Estimated due date: 07 Apr 2027 - 40 weeks from LMP.
The result is the verified Build 0232 output for this exact scenario. It should be interpreted with the displayed inputs, assumptions and limitations rather than as context-free advice.
Assumptions
- The entered values are accurate measurements/dates and fall within the intended population or use case of the cited method.
- The result is an estimate or summary; individual physiology, measurement conditions and clinical context can materially change interpretation.
Limitations
- This ToolLott page is not a diagnostic device and does not provide medical advice, diagnosis or treatment recommendations.
- Seek appropriate healthcare advice for symptoms, abnormal readings, pregnancy/fertility decisions, medication/exercise safety or results that are inconsistent with your circumstances.
Common questions
What does the Pregnancy Calculator actually do?
Calculate the conventional estimated due date of 280 days from the first day of the last menstrual period, with simple planning milestones. The methodology documents the production calculation or transformation rather than a generic description.
Does the worked example match the real ToolLott tool?
Yes. It is tied to the passed production QA fixture for Build 0232, including the expected summary.
What should I verify before relying on the output?
Check the entered values, stated assumptions, support boundaries and any authoritative sources linked on the page; independently review high-stakes use.
Methodology sources
Related ToolLott tools
A realistic way Mia could use this tool
Mia is a person tracking general wellness information.
Mia has a recorded last-menstrual-period date of 1 July 2026 and wants the conventional estimated due-date arithmetic for appointment planning before clinical dating is confirmed.
Mia enters 1 Jul 2026. The calculator adds the conventional 280 days (40 weeks) and also derives simple 12-week and 20-week planning markers from the same LMP date.
The estimated due date is 7 Apr 2027. Mia has a transparent date calculation for early planning, while the page clearly notes that ultrasound and clinical information can change pregnancy dating.
Fictional scenario using realistic example data. For Ready tools, the worked result is tied to the tested example shown in the tool. Replace the figures with your own inputs and independently verify important professional, financial, legal, health or safety decisions.
What this calculator is for
Use it to calculate the conventional estimated due date of 280 days from the first day of the last menstrual period, with simple planning milestones.
It sits within ToolLott’s Health Calculators collection, where you can also calculate BMI, BMR, body fat, calorie needs, heart-rate zones, ovulation dates and pregnancy dates for general information.