Science-based pregnancy tools for due dates, weekly progress tracking, and prenatal planning. Reviewed against ACOG 2026 guidelines.
Whether you're newly pregnant trying to figure out your due date, mid-pregnancy tracking weekly milestones, or just curious about conception dates and trimester progress, our pregnancy calculators give you accurate, evidence-based answers — all free, no signup, and your data never leaves your browser.
Knowing your due date is the foundation of pregnancy planning. Every prenatal appointment, test, and milestone is scheduled relative to it — from your first ultrasound at 8-13 weeks to the glucose challenge at 24-28 weeks to the GBS test at 35-37 weeks. A reliable pregnancy calculator gives you this anchor immediately, before your first doctor's visit can confirm it.
Beyond the due date itself, our calculator shows you where you are right now — which trimester, which week, how far along, and how much time remains. It also generates the appointment schedule your provider would normally hand you in printed form, so you can plan ahead and never miss a critical test window.
| Stage | Weeks | Key Developments |
|---|---|---|
| 1st Trimester | 1-13 | Implantation, organ formation, heartbeat begins |
| 2nd Trimester | 14-27 | Anatomy scan, gender visible, first movements felt |
| 3rd Trimester | 28-40 | Rapid growth, lung development, delivery prep |
| Early Term | 37-38+6 | Baby considered ready but earlier than optimal |
| Full Term | 39-40+6 | Optimal delivery window for best outcomes |
| Late Term | 41-41+6 | Additional monitoring typically begins |
| Post-Term | 42+ | Induction usually recommended |
For detailed calculations and a personalized timeline, use our Pregnancy Due Date Calculator.
Yes, completely free. No signup, no email required. All calculations happen in your browser, and no personal data is stored or transmitted.
No. Our calculators provide educational estimates based on standard medical formulas. Your healthcare provider will confirm your due date with an early ultrasound and provide personalized guidance throughout your pregnancy. Always follow your provider's specific recommendations.
The math is exact, but the prediction is an estimate. Only about 4% of babies are born on their exact due date — most arrive within 1-2 weeks of it. Early ultrasound dating (8-13 weeks) is more accurate than LMP-based calculations.
An early ultrasound is the most reliable way to date a pregnancy, particularly with irregular cycles, and your care provider's estimate always takes precedence over a calculated one. Our ovulation calculator covers the cycle side, and the age calculator is useful for working out dates across a calendar.
Get your personalized due date with full pregnancy timeline in under a minute. Free and instant.
Open Due Date Calculator →Pregnancy dating conventionally starts from the first day of the last menstrual period rather than from conception, which typically occurs about two weeks later. This means the first two weeks of a forty-week pregnancy precede conception, a convention that surprises many people and reflects the fact that the last period is a date most people can identify while conception often is not.
A due date calculated this way is an estimate of the middle of a range, not an appointment. Only a small minority of babies arrive on the estimated date, and a healthy full-term birth spans several weeks either side of it.
| Milestone | Timing | Note |
|---|---|---|
| First trimester | Weeks 1 to 13 | Dated from last menstrual period |
| Second trimester | Weeks 14 to 27 | Often the most settled period |
| Third trimester | Weeks 28 to 40 | Full term is generally 37 to 42 weeks |
| Estimated due date | Week 40 | A midpoint estimate, not a fixed date |
Early ultrasound measurement is generally more accurate than calculation from the last period, particularly for people with irregular cycles. If a scan gives a different date from a calculator, the clinical estimate is the one to use.