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Pregnancy & Baby
How Far Along Am I Calculator — Pregnancy Weeks, Days & Trimester
Your current pregnancy week, days, and trimester today — counted the way your provider counts, using ACOG dating
"How far along am I?" is the question every newly pregnant person types at 2 a.m. — and the answer isn't a single date, it's a right-now snapshot: how many weeks and days into the pregnancy you are today. That number is called your gestational age, and in the United States it's measured the way the American College of Obstetricians and Gynecologists (ACOG) standardizes it — counting forward from the first day of your last menstrual period (LMP), not from conception.
The math is simple. Gestational age = today − first day of LMP, expressed as completed weeks plus leftover days (for example, 17 weeks 3 days, written 17w3d). Because a full-term pregnancy is 40 weeks (280 days) by this count, your gestational age also tells you how much road is left to your due date: days remaining = 280 − days since LMP.
This tool is deliberately different from a due date calculator. A due-date tool hands you one calendar date months from now; this one answers the more immediate question — where am I in the pregnancy at this moment, and which trimester is that? It owns the how-far-along question and updates every day on its own.
Your trimester falls straight out of the week count, using the standard ACOG boundaries:
- First trimester — 0w0d through 13w6d (the end of week 13)
- Second trimester — 14w0d through 27w6d (the "honeymoon" weeks)
- Third trimester — 28w0d through 40w and beyond, until birth
Don't already know your LMP? Many people only remember the due date their provider gave them at the dating scan. So this calculator works both ways: enter your LMP, or switch to due-date mode and we'll work backward — your LMP is simply the due date minus 280 days — then count forward to today exactly the same way.
Worked example. Your LMP was March 1, 2026 and today is June 19, 2026 — that's 110 days since LMP, or 110 ÷ 7 = 15 weeks 5 days along, squarely in the second trimester, with 280 − 110 = 170 days left to the December 6 due date.
The single biggest mix-up: people assume "how far along" is measured from conception and try to subtract two weeks. Don't. LMP dating already bakes in those ~2 weeks before ovulation, which is exactly why the figure here matches what your provider quotes at appointments.
This is an informational estimate, not a medical diagnosis or a substitute for prenatal care. Your true gestational age can shift by several days once an early ultrasound measures the baby directly — and if it does, your provider's ultrasound-based dating, not this LMP estimate, is the number your care follows.
Calculator
Fill in the fields and click "Calculate" for instant results.
📰 Formula
• Gestational age = today − first day of LMP, shown as completed weeks + leftover days • Weeks = floor(days since LMP ÷ 7), Days = (days since LMP) mod 7 • Due-date mode: LMP = due date − 280 days, then count forward to today • Days remaining = 280 − days since LMP (negative means past the due date) • Trimester (ACOG): 1st = 0w0d–13w6d · 2nd = 14w0d–27w6d · 3rd = 28w0d–40w+
📰 Formula
• Gestational age = today − first day of LMP, shown as completed weeks + leftover days • Weeks = floor(days since LMP ÷ 7), Days = (days since LMP) mod 7 • Due-date mode: LMP = due date − 280 days, then count forward to today • Days remaining = 280 − days since LMP (negative means past the due date) • Trimester (ACOG): 1st = 0w0d–13w6d · 2nd = 14w0d–27w6d · 3rd = 28w0d–40w+
🧪 Worked examples
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Example 2
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Example 3
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Example 4
⚠️ Common mistakes
- Counting from conception and shaving off ~2 weeks — LMP dating already includes them.
- Entering the day your last period ended instead of the first day it started.
- Confusing 'weeks pregnant' (completed weeks) with the week you're 'in' — being 15w5d means you're in your 16th week.
- Treating the gestational age as exact when an early ultrasound can move it by several days.
- Mixing up trimesters — the 2nd trimester starts at 14w0d, not at week 12 or week 13.
💡 Tips
- Enter the first day of your last period — not the day bleeding stopped, and not your guessed ovulation day.
- If you only know your due date, switch to due-date mode; the tool back-calculates your LMP automatically.
- Re-check after your dating scan — if the ultrasound moves your due date, use that new date here for accuracy.
- Remember the off-by-one: at 15w5d you've completed 15 weeks and are living through your 16th.
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❓ Frequently asked questions
How do I figure out how far along I am in pregnancy?
Count the days from the first day of your last menstrual period (LMP) to today, then divide by 7 to get whole weeks plus leftover days — for example 110 days is 15 weeks 5 days. This is your gestational age, the same figure your provider quotes. It's an informational estimate, not a medical diagnosis.
Is 'how far along' measured from conception or my last period?
From your last period. ACOG and US obstetric practice date pregnancy from the first day of the LMP, which is about two weeks before conception actually happens. That's why your 'weeks along' number runs roughly two weeks ahead of the embryo's biological age — and why you shouldn't subtract those weeks.
What week of pregnancy am I in if I'm 15 weeks 5 days?
You've completed 15 weeks and you're in your 16th week. 'Weeks along' counts completed weeks, so 15w5d means 15 full weeks are done and you're partway through the next one. This off-by-one trips up a lot of people.
Which trimester am I in?
Using ACOG boundaries: the first trimester runs from 0w0d through 13w6d, the second from 14w0d through 27w6d, and the third from 28w0d to birth. This calculator flags your current trimester automatically from your gestational age today, and updates as the days pass.
How many days until my due date?
A full-term pregnancy is 280 days (40 weeks) from your LMP, so days remaining = 280 minus the days since your LMP. If the result is negative, you're past the estimated due date. Only about 1 in 20 babies actually arrives on the exact date.
Can I use this if I only know my due date, not my last period?
Yes — switch to due-date mode. The tool sets your LMP to the due date minus 280 days, then counts forward to today exactly the same way. This is handy when your provider gave you a due date at a scan but you never tracked your period.
How accurate is this gestational age estimate?
It's precise as a day count from the date you enter, but the date itself can be off. An early ultrasound that measures the baby directly can shift your gestational age by several days, and if it does, that ultrasound dating becomes the one your care follows. Treat this as a helpful estimate, not a diagnosis.
What's the difference between this and a due date calculator?
A due date calculator gives you a single future date — the day you might deliver. This 'how far along' calculator answers the right-now question: how many weeks and days into the pregnancy you are today, and which trimester that is. They use the same 40-week math but answer different questions.
Why does my number change by a day from other apps?
Small differences usually come from time zones, whether a tool counts 'today' inclusively, or whether it adjusts for your cycle length. This calculator counts whole calendar days in UTC from your LMP to today. A day's variance is normal and clinically insignificant.