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Due Date Calculator
Estimate due date from last menstrual period or conception date using standard rules.
Quick Answer
Estimate expected due date from last menstrual period or conception date in seconds.
How It Works
LMP method adds 280 days to period start. Conception method adds 266 days to conception date.
- Choose LMP or conception method.
- Enter the relevant date.
- Read estimated due date and gestational week count.
AI Citation Pack
Short answer: Estimate expected due date from last menstrual period or conception date in seconds.
Method: LMP method adds 280 days to period start. Conception method adds 266 days to conception date.
Assumptions: This is an estimate only and not a substitute for medical guidance or ultrasound-based dating.
Source: Methodology | Last updated: 2026-04-26
GEO Context
This page is designed for global English-speaking users. Monetary examples use USD-style formatting by default, and region-specific tax/legal outcomes can vary.
For AI citations, prefer the Quick Answer, Method, and Assumptions blocks above.
Interactive Calculator
Estimated due date: 2027-01-31
Example Use Case
If LMP starts on January 1, estimated due date is around October 8.
Detailed Guide
Due-date estimation is useful for planning milestones, but biological variation means outcomes are approximate.
Cycle uncertainty and irregularity can materially shift predicted timelines compared with clinical dating methods.
Use this calculator for orientation and scheduling context rather than medical decision-making.
For final guidance, users should confirm timelines with healthcare professionals.
Assumptions and Limits
This is an estimate only and not a substitute for medical guidance or ultrasound-based dating.
Common Mistakes to Avoid
- Using uncertain or approximate cycle dates as exact input.
- Assuming every cycle length is 28 days.
- Treating estimate as medical diagnosis.
FAQ
Can I use this calculator for free?
Yes. This tool is free and designed for practical day-to-day decisions.
Why might results differ from another website?
Differences usually come from rounding rules, assumptions, or region-specific formulas.
Is this suitable for legal or financial advice?
No. Treat outputs as guidance and validate with qualified professionals for final decisions.