Pregnancy Calculator — All-in-One

Use the Pregnancy Calculator — All‑in‑One

How to Use Pregnancy Calculator — All-in-One

1. Step 1: Choose method

   Select LMP, Conception, Ultrasound, IVF, or Due Date.

2. Step 2: Enter dates

   Provide the first day of last period, conception, ultrasound, or due date.

3. Step 3: Adjust cycle (optional)

   If using LMP, set your average cycle length to refine EDD.

4. Step 4: Set as‑of date

   Pick today or any date to see the exact weeks and days.

5. Step 5: Calculate

   Tap Calculate to get EDD, gestational age, trimester, and milestones.

6. Step 6: Review & share

   Copy your summary or share the link with your partner or provider.

Key Features

• EDD by LMP, conception, ultrasound, IVF
• Gestational age in weeks and days
• Trimester and key milestone dates
• As‑of date control and progress bar
• Mobile‑first, private, no data saved

Understanding Results

Formula

The pregnancy calculator applies standard clinical rules to estimate key dates. By default (LMP method), it uses Naegele’s rule: the estimated due date (EDD) is the first day of your last menstrual period plus 280 days (40 weeks). If your average cycle length differs from 28 days, the tool shifts the EDD by the difference so longer cycles move the due date later and shorter cycles move it earlier. When you select Conception, the calculator assumes clinical gestational age starts 14 days before conception and sets EDD to conception + 266 days. With an Ultrasound measurement, you enter the scan date and the gestational age read on the report (weeks + days). The tool back‑dates the clinical LMP from that measurement and projects the EDD 280 days from that computed LMP. The IVF method accounts for embryo age at transfer (day‑3 or day‑5) and uses the standard EDD formula for IVF: EDD = transfer + (266 − embryo age in days).

Reference Ranges & Interpretation

Gestational age is reported in weeks and days as of the date you choose (default is today). Trimesters follow common cutoffs: first trimester through 13 weeks 6 days; second trimester 14 weeks 0 days through 27 weeks 6 days; third trimester starts at 28 weeks. The timeline in your results highlights key points many clinicians discuss, such as the end of the first trimester (~14 weeks), the anatomy scan (~20 weeks), glucose screening (24–28 weeks), and the start of the third trimester (28 weeks). “Full term” is commonly considered 39–40 weeks. While many pregnancies deliver around the EDD, normal spontaneous birth may occur before or after this date.

Dating methods have different accuracy. LMP assumes regular ovulation roughly 14 days before the next period. Early first‑trimester ultrasound is often the most precise way to date pregnancy because crown‑rump length has a narrow normal range in early weeks. If an ultrasound due date differs from LMP by more than a small margin, clinicians may adopt the ultrasound date. These conventions vary by organization and gestational age at the time of scan.

Assumptions & Limitations

Results are for planning and education only and do not replace clinical care. Irregular cycles, recent hormonal contraception, breastfeeding, or uncertain dates can all reduce LMP accuracy. Ultrasound‑based estimates depend on the scan date and measurement quality. IVF timing depends on precise transfer details. If you are unsure about your dates, have symptoms that concern you, or are in a high‑risk pregnancy, talk with your clinician. For general background, see guidance from professional organizations such as ACOG and WHO. External links open in a new tab: ACOG due date methods and WHO recommendations.

Complete Guide: Pregnancy Calculator — All-in-One

Use our pregnancy calculator to estimate due date (EDD), track weeks and days of pregnancy, and see key milestones on a clean timeline. Private, accurate.

What this pregnancy calculator estimates

The goal is simple: give you the dates you care about on one screen. The tool estimates your due date (EDD), shows gestational age in weeks and days for any date you choose, identifies your current trimester, and highlights milestone dates most people track during pregnancy.

You can enter the first day of your last period (LMP), a known conception date, an early ultrasound result, IVF transfer details, or a known due date. The calculator adapts to the method you pick and keeps the math consistent—no guessing, no manual counting.

All calculations run in your browser. We do not store or transmit your information. That means you can explore different dates freely and privately to see how your week‑by‑week timeline shifts.

Methods: LMP, Conception, Ultrasound, IVF, EDD

LMP: Enter the first day of your last menstrual period and, if needed, adjust your average cycle length. The tool applies Naegele’s rule (LMP + 280 days) and shifts for cycles longer or shorter than 28 days.

Conception: If you know the day fertilization likely occurred, enter that date. The calculator sets the clinical LMP 14 days before and calculates EDD as conception + 266 days.

Ultrasound: With a first‑trimester scan, enter the scan date and the gestational age printed on your report (weeks + days). The tool back‑dates an LMP and projects the EDD 280 days from that point. Early ultrasounds are often the most precise for dating.

IVF: For embryo transfer, choose day‑3 or day‑5 and enter the transfer date. The standard convention is EDD = transfer + (266 − embryo age in days). The calculator applies that and shows your full timeline.

Known EDD: If your provider has already assigned a due date, select EDD and enter that date directly. The tool will compute the corresponding LMP, conception estimate, and current week.

How EDD is calculated

By default, the calculator uses Naegele’s rule, which is widely taught and easy to understand: due date = LMP + 280 days (40 weeks). Because clinical gestational age is counted from the LMP and not the conception date, this formula lines up with how your provider usually writes gestational age in the chart.

Cycle length matters when you ovulate reliably earlier or later than day 14. If your cycle averages 32 days, you may ovulate around day 18, and shifting the EDD by four days can better reflect your personal rhythm. If your cycle averages 24 days, the shift goes in the other direction. The cycle control in the calculator lets you tune this without doing the math yourself.

Ultrasound dating is different: we start from the measured gestational age on the scan date, derive a clinical LMP from that, and project forward. If an early ultrasound substantially disagrees with an LMP‑based date, many clinicians adopt the ultrasound date because early fetal growth has tight variance.

Weeks + days and trimester boundaries

Gestational age is typically shown as “weeks + days,” for example, 12w4d. That means 12 full weeks have passed since the LMP, plus 4 additional days. Our pregnancy calculator updates this for any as‑of date you choose, so you can check today or plan for a future appointment.

Trimesters are labeled by ranges most organizations recognize: First trimester through 13w6d, second trimester 14w0d through 27w6d, and third trimester beginning at 28w0d. The tool displays your current trimester and shows when each boundary will occur on your timeline.

Milestones on the timeline

Milestones help you see the road ahead. Common touchpoints include the end of the first trimester (~14 weeks), the anatomy scan (~20 weeks), glucose screening (24–28 weeks), start of the third trimester (28 weeks), and the “full‑term” period (39–40 weeks). The calculator lists these dates and displays your progress bar so you can see where you are at a glance.

Every pregnancy is different. These dates are not appointments by themselves, but they often align with typical schedules your provider may discuss with you. Use the timeline as a planning helper alongside your own care plan.

Irregular cycles and choosing a method

If your periods vary, the LMP method may be less precise unless you adjust the average cycle length. Consider switching to Conception (if the date is known) or Ultrasound, especially an early first‑trimester scan. Those inputs reduce uncertainty because they bypass assumptions about ovulation timing.

If you are tracking cycles, tools like the ovulation calculator and cycle length calculator can help you learn your pattern. For planning, the conception date calculator can translate a known event into the clinical dates used by this tool.

IVF dating specifics

With IVF, dating centers on the embryo’s age at transfer. A day‑5 blastocyst is five days past fertilization when transferred; a day‑3 embryo is earlier. Our pregnancy calculator uses the standard convention: EDD = transfer + (266 − embryo days at transfer). It also derives the corresponding clinical LMP so your week count and trimester view remain consistent with routine charting.

If you had a frozen transfer, the same rule applies. Because IVF records are precise, this method usually yields consistent dates. Your clinic may still confirm with an early ultrasound and, if necessary, harmonize dates in the medical record.

Examples: three common scenarios

Example 1 — LMP + 28‑day cycle: LMP April 2 → EDD January 7 (280 days later). On June 15, the calculator shows 10w6d, second trimester starting around July 7.

Example 2 — Conception known: Conception May 10 → clinical LMP April 26 → EDD February 1. On September 1, the readout shows 18w2d, with the 20‑week anatomy scan date clearly marked.

Example 3 — Ultrasound dating: Scan on July 8 reads 8w4d → clinical LMP May 12 → EDD February 16. If your prior LMP‑based EDD differs by more than a small margin, your provider may opt to use the ultrasound date.

Planning tips and next steps

Use the as‑of date control to preview future weeks, schedule time‑sensitive tasks, and coordinate travel or leave. Because your week and trimester update instantly, you can verify how plans line up without manual counting.

If you need a focused view of a single concept, the due date calculator (EDD) and the pregnancy week calculator offer streamlined screens. If you are early and timing a test, the pregnancy test calculator estimates when home tests are most informative. For trimester boundaries alone, try the trimester calculator.

If your cycles are shifting after stopping birth control or during postpartum, the period calculator and menstrual cycle calculator can help you regain a consistent baseline.

Related tools

Explore these calculators to round out your planning: Ovulation Calculator, Conception Date Calculator, Pregnancy Due Date Calculator (EDD), Pregnancy Week Calculator, Trimester Calculator, and Pregnancy Test Calculator. All internal links open within the site and use trailing slashes.

Nothing here is medical advice. Use this pregnancy calculator to plan and to ask clearer questions. For medical decisions, your own clinician is the right resource.

Frequently Asked Questions