Best Pregnancy Due Date Calculators — Free & Accurate

Finding out your expected due date is one of the first things you do after a positive pregnancy test. While your doctor will confirm the date (usually with an ultrasound), a due date calculator gives you an immediate estimate so you can start planning.

Here's how the best free pregnancy due date calculators compare.

How Due Date Calculation Works

The standard method is Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation on day 14.

Due Date = LMP + 280 days

More accurate calculators adjust for cycle length. If your cycle is 32 days instead of 28, ovulation likely occurs on day 18, shifting the due date forward by 4 days.

Top Pregnancy Due Date Calculators Compared

Feature	CalcHub	BabyCenter	What to Expect	Pampers	WebMD
LMP-based calculation	Yes	Yes	Yes	Yes	Yes
Cycle length adjustment	Yes	No	No	No	No
IVF transfer date option	Yes	Yes	No	No	No
Trimester breakdown	Yes	Yes	Yes	Yes	Yes
Week-by-week development	No	Yes	Yes	Yes	Yes
Conception date estimate	Yes	Yes	Yes	Yes	Yes
Ad-free	Yes	No	No	No	No
No account required	Yes	Partial	Partial	Partial	Yes
Mobile-friendly	Yes	Yes	Yes	Yes	Yes

CalcHub Due Date Calculator

Strengths: The CalcHub pregnancy due date calculator calculates your due date from LMP with cycle length adjustment — a feature most competitors skip. Also supports calculation from conception date or IVF transfer date. Shows your current week, trimester, and days remaining. Clean, fast, completely free, no account needed, no ads. Limitations: Doesn't include week-by-week baby development content. It's a calculator, not a pregnancy tracking app.

BabyCenter Due Date Calculator

Strengths: Pairs the due date calculation with extensive week-by-week development content — what your baby looks like, how big they are, what symptoms to expect. A complete pregnancy information platform built around the due date. Limitations: Heavy advertising. Requires creating an account for full features. The due date calculator itself doesn't adjust for cycle length — assumes a standard 28-day cycle.

What to Expect Due Date Calculator

Strengths: Backed by the well-known pregnancy book brand. Provides detailed trimester and week-by-week information. Strong community forums for expecting parents. Limitations: The due date calculation is basic (no cycle length adjustment). Account creation is pushed early. Ad-heavy experience.

Pampers Due Date Calculator

Strengths: Simple and approachable interface. Good visual week-by-week timeline. Links to relevant parenting content. Limitations: Limited calculation options — LMP only, no cycle adjustment. The experience is intertwined with Pampers marketing. Requires email for full features.

Verdict

For accurate due date calculation: CalcHub — cycle length adjustment and multiple input methods give the most accurate estimate, with zero distractions. For pregnancy tracking and weekly updates: BabyCenter or What to Expect — when you want ongoing content alongside your due date, and don't mind creating an account. Important note: All calculators provide estimates. Only about 5% of babies arrive on their due date. Most full-term births occur between 37 and 42 weeks.

How accurate are due date calculators?

Using LMP with a 28-day cycle assumption, the estimate is within a 5-day window for most pregnancies. Cycle length adjustment improves accuracy. Ultrasound dating in the first trimester is the most accurate method — your doctor will use this to confirm or adjust the calculated date.

Should I use my LMP or conception date?

If you know your exact conception date, use it — it eliminates the cycle-length variable. If you're unsure, LMP is the standard method. Most women use LMP because conception date is rarely known precisely.

What if my cycle is irregular?

Irregular cycles make LMP-based calculation less reliable. If your cycles vary significantly (more than a week), an early ultrasound is the best way to establish your due date. A calculator can still give you a starting estimate.

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• BMI Calculator — track healthy weight during pregnancy
• Date Difference Calculator — count days between any two dates