Pregnancy Calculator

What it does

Estimate your due date, current week of pregnancy, and trimester from either the first day of your last menstrual period (LMP) or a known conception date. Uses the standard Naegele's rule of LMP + 280 days, the same formula most practitioners and apps use for a first-look estimate.

This is a planning tool, not a medical device — real due dates shift based on ultrasound dating, ovulation timing, and individual cycle variation. For fertility-window planning before conception, use the ovulation calculator; for ongoing appointments and milestones, keep it beside your prenatal-care schedule.

How to use it

1. Pick LMP or conception-date mode.
2. Enter the relevant date.
3. Read your estimated due date and current pregnancy week.
4. See which trimester you're in and the estimated conception date.

When to use this tool

• Preparing questions for a doctor or registered dietitian appointment.
• Reality-checking a wearable or app’s built-in estimate.
• Establishing baseline metrics for a fitness or nutrition program.
• General-population health planning (not diagnostic).

When not to use it

• Pediatric, geriatric, or pregnant users where adult formulas are inaccurate.
• Diagnostic decisions — consult a doctor.
• When the metric in question depends on lab work the calculator can’t see.
• Performance medicine for elite athletes — use sports-medicine specialists.

Common use cases

• Quick calculation during a typical workday
• Pre-decision sanity-check on inputs and outputs
• Educational use — demonstrating the underlying concept
• Onboarding a colleague who needs the same calculation/conversion