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Pregnancy Due Date Calculator — Weeks, Trimester, Baby Development

Pregnancy due date calculator — track weeks, trimester, baby development by week.

  • Runs locally
  • Category Calculator
  • Best for Getting a realistic range before a purchase, plan, workout, or schedule decision.
Estimated due date
2027-04-08 (Thursday)
Baby zodiac: Goat (羊)
Current gestational age
0weeks 0days
Trimester
First
Days until due
280
Weeks until due
40
This week's development
Week 1 is counted from the first day of the last menstrual period. Conception has not yet occurred — the body is preparing the uterine lining.
Your privacy
The date you enter is never uploaded. All calculations run locally in your browser — no analytics, no server, no medical record.
Educational use only. This tool is NOT a substitute for prenatal care. Ultrasound dating by your obstetrician is more accurate than any formula, especially after a first-trimester scan.

What this tool does

Free online pregnancy due date calculator. Choose your method — last menstrual period (LMP, +280 days by Naegele's rule), known conception date (+266 days), or a recent ultrasound (date + reported gestational age) — and instantly see your estimated due date, current gestational age in weeks and days, trimester, baby's Chinese zodiac for the due- date year, and a short, factual fetal-development summary for every one of the 40 weeks (paraphrased from public ACOG and WHO guidance). Days and weeks until due update in real time, and the tool honors post-term arithmetic if your due date has passed. All calculation runs locally in your browser — the date you enter is never uploaded, never logged, never sent anywhere. This is an educational reference; it does not replace prenatal care or ultrasound dating by your obstetrician, which is more accurate than any formula.

Tool details

Input
Numbers
The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output
Live result
The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy
Browser-side processing
The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share
No account required
Open the page and use it; whether results survive refresh depends on the tool.
Performance budget
Initial JS <= 18 KB
No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit
Calculator · Content Creator
Category and role tags drive related tools, internal links, and quick fit checks.

How to use

  1. 1. Input

    Paste or drop your content into the tool panel.

  2. 2. Process

    Click the button. All processing is local in your browser.

  3. 3. Copy / Download

    Copy the result or download to disk in one click.

How Pregnancy Due Date Calculator fits into your work

Use it for fast estimates, comparisons, and planning numbers before you make the final call.

Calculation jobs

  • Getting a realistic range before a purchase, plan, workout, or schedule decision.
  • Comparing scenarios by changing one input at a time.
  • Turning rough assumptions into a number you can discuss.

Calculation checks

  • Double-check units, dates, rates, and rounding assumptions.
  • Treat health, finance, tax, and legal outputs as planning aids, not professional advice.
  • Save the inputs that produced an important result so you can reproduce it later.

Good next steps

These links move the current task into a more complete workflow.

  1. 1 Age Calculator Calculate your exact age — years, months, days, hours. Compare two dates or count to a future date. Open
  2. 2 Date Difference Calculator Days / weeks / months / years between two dates — plus business-days mode — browser-only Open
  3. 3 Lunar Calendar Converter (Chinese Nongli) Gregorian ⇄ Chinese Lunar (Nongli) calendar — bi-directional, accurate 1900-2100. Open

Real-world use cases

  • Booking your first prenatal appointment in the right week

    You got a positive test and want to schedule the dating scan, which clinics usually do between weeks 8 and 13. Enter your LMP, see you're at 6 weeks 4 days today, and book the scan for about two weeks out so you land in the 8-to-13 window instead of showing up too early to measure crown-rump length.

  • Re-anchoring dates after an ultrasound disagrees with your LMP

    Your LMP put you at 11 weeks, but the dating scan measured 10w2d, a 5-day gap that crosses the ACOG 7-day re-date threshold only if it had been 8 days. Switch to "Last ultrasound" mode, enter the scan date and the reported 10w2d, and the tool resets your due date to match the scan so your follow-ups line up.

  • Planning maternity leave around the 37-week full-term mark

    Your employer needs a leave start date. Your due date lands on March 14, so week 37 (full term begins) falls around February 21. You set your last working day for February 18 to bank a few buffer days, and use the week countdown to know you have 19 weeks left to finish handoff docs before then.

  • Tracking a post-term pregnancy past the due date

    You hit 40 weeks 0 days with no labor. The tool keeps counting: today it shows 40 weeks 3 days, three days post-term. That number matters because most providers discuss induction between 41 and 42 weeks, so you watch the count climb and know roughly when that conversation is coming at your next visit.

Common pitfalls

  • Confusing gestational age with embryo age. "10 weeks pregnant" means 10 weeks from LMP, but the embryo is about 8 weeks old; don't panic if a scan reports a smaller number.

  • Entering a long-cycle LMP without adjustment. If your cycle runs 35 days, the standard 280-day count puts your due date ~7 days too early; shift your LMP input or use a scan to re-date.

  • Treating the LMP estimate as final. A first-trimester ultrasound dates within ±5 days versus ±2 weeks for LMP; if they differ by more than 7 days, your provider uses the scan, not this tool.

Privacy

Everything runs in your browser. The LMP, conception, or ultrasound date you type stays on the page and is never uploaded, logged, or attached to any analytics event; open the network tab and you'll see no request fires when you change inputs. If you turn on share links, the date you entered does go into the URL so the result is reproducible, so don't share that link if you'd rather keep the date private. The page also works offline once loaded.

FAQ

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Made by Toolora · 100% client-side · Updated 2026-07-02