Pregnancy Due Date Calculator: Find Out When Your Baby Is Coming
Becoming pregnant is one of life’s most exciting journeys — and naturally, one of the first questions every mom-to-be asks is: “When is my baby coming?”
That’s exactly what our pregnancy due date calculator is here for!
With just a few quick details — like the first day of your last period and your average cycle length — you can get a close estimate of your baby’s expected arrival. It’s simple, free, and gives you a peek into your pregnancy timeline so you can start planning (and daydreaming!) about meeting your little one.
Your pregnancy due date marks 40 weeks from the first day of your last period, but every pregnancy is unique. Some babies make their grand entrance a little earlier, while others take their sweet time. Think of this date as your baby’s “guestimate” — a friendly countdown to the moment your world changes forever.
Once you know your due date, you’ll also discover which trimester you’re in, when key milestones happen (like your first ultrasound or when you might start feeling those tiny kicks), and when to expect your baby bump to really show.
Ready to find out when you’ll finally hold your bundle of joy?
Scroll down, use the pregnancy due date calculator, and let the countdown begin!
What Is a Due Date?
Your due date is the estimated day your baby will arrive — usually about 40 weeks from the first day of your last menstrual period. It’s not an exact science, but a helpful guide for you and your doctor to track your pregnancy week by week.
Most babies are born within a week or two of their due date, so think of it as your little one’s “expected debut.” Knowing your due date helps you plan everything — from checkups and ultrasounds to when to pack your hospital bag!
How to Use the Pregnancy Due Date Calculator
Using the pregnancy due date calculator is super simple — no medical math needed!
Here’s how to find out your baby’s estimated arrival date in seconds:
Enter the first day of your last period.
This is the date your last menstrual cycle started — it helps the calculator figure out when ovulation and conception likely happened.Add your average cycle length.
Most women have a 28-day cycle, but if yours is longer or shorter, just adjust the number to match what’s normal for you.Click “Calculate My Due Date.”
In an instant, you’ll see your estimated due date, what week of pregnancy you’re in, and a few key milestones to look forward to (like when you might start feeling those first baby flutters ).
That’s it! It’s an easy, reliable way to get a quick estimate before your first doctor visit — and it’s totally free to use anytime.
Due Date Calculator — Momsy
Enter the first day of your last period and your average cycle length. We’ll estimate your due date and show key milestones.
How the Pregnancy Due Date Calculator Works
Our pregnancy due date calculator follows the same method doctors use — something called Naegele’s Rule.
It estimates your due date by adding 280 days (or 40 weeks) to the first day of your last menstrual period.
Why start counting from your period, not the day you actually conceived?
Because ovulation (and conception) usually happens about two weeks after your period starts — and not every woman knows her exact ovulation date.
So doctors and calculators alike use your LMP (last menstrual period) as a consistent starting point.
Of course, every pregnancy is unique.
Some babies arrive a bit early (around week 37) and others take their time (up to week 42).
That’s why your due date is best seen as an estimate, not a deadline — a sweet countdown that helps you and your doctor track how your baby is growing week by week.
Behind the scenes, the calculator also adjusts for your cycle length.
If your cycle is longer or shorter than 28 days, it adds or subtracts those extra days so your due date fits your body’s rhythm.
What Affects Your Due Date?
Even though our pregnancy due date calculator gives a solid estimate, every pregnancy has its own timeline — and a few things can shift that date a little. Here are the most common reasons your due date might change:
Irregular menstrual cycles
If your cycle is shorter or longer than the typical 28 days, your ovulation (and conception) happens earlier or later — which can move your due date by several days.Late or early ovulation
Some women ovulate later than average, especially after stopping birth control or during their first few cycles. That can make your pregnancy seem “off” by a week or two at first.Ultrasound adjustments
During your first prenatal ultrasound, your doctor measures your baby’s size and may update your due date for more accuracy. It’s totally normal — it just means your provider has better info about your baby’s growth.Multiple pregnancies (twins or more!)
If you’re carrying twins or triplets, your babies may arrive earlier than 40 weeks, since multiple pregnancies often come a bit sooner.Natural variation
Every body — and every baby — is different. Only about 5% of babies are born exactly on their due date! So try not to focus too much on one specific day.
Your due date is best thought of as a beautiful estimate — a reminder that your baby will arrive when they’re ready.
What Happens After You Find Your Due Date
So now that you’ve used the pregnancy due date calculator and discovered your baby’s estimated arrival — what’s next?
This is where the fun (and planning!) really begins.
Knowing your due date helps you schedule doctor visits, track each trimester, and understand when exciting milestones are coming up — like hearing your baby’s heartbeat for the first time or feeling those sweet little kicks.
It also helps you prepare emotionally and practically. You can start setting up your nursery, planning your maternity leave, and creating a birth plan that feels right for you and your family.
Remember, your due date isn’t a promise — it’s a beautiful countdown to the moment your life changes forever. Whether your little one arrives early, late, or right on time, they’ll show up exactly when they’re meant to.
Ready to take the next step?
Explore more on Momsy — from week-by-week pregnancy guides to self-care tips and baby prep checklists.
Your motherhood journey starts right here.
