Due Date Calculator

Estimate your pregnancy due date and current gestational age from your last menstrual period. Free, instant, no signup.

How to use the Due Date Calculator

  1. Enter your values. Fill in the fields with your numbers.
  2. Calculate. Press Calculate to run the due date calculator.
  3. Use the result. Copy the result or try a related tool next.

Why use our Due Date Calculator

Instant results. Enter your figures and the due date calculator returns an answer in seconds.
Free & private. Runs in your browser — no signup, and nothing is sent to a server.
Accurate. Uses standard formulas so you can rely on the numbers.

Free to use — premium coming soon

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About the Due Date Calculator

The Due Date Calculator estimates when your baby is likely to arrive, expressed as an estimated date of delivery (EDD). Enter the first day of your last menstrual period (LMP) and the tool returns a date roughly 40 weeks (280 days) later. This follows Naegele's rule, the standard method clinicians have used for over two centuries: take the first day of your LMP, add seven days, subtract three months, then add one year. The result is the same 280-day countdown your doctor or midwife uses at your first appointment, giving you an early reference point before any scan confirms the date.

Reach for this calculator the moment you suspect or confirm a pregnancy and want a concrete timeline to plan around. It helps you work out how far along you are, when each trimester begins and ends, and roughly when to schedule prenatal visits, the anatomy scan, or maternity leave. It is also useful if your cycle is longer or shorter than 28 days, because you can compare the LMP-based estimate against a conception date if you happen to know it. Many parents simply use it for peace of mind and to start counting down the weeks.

Under the hood the tool does straightforward date arithmetic rather than guesswork. The LMP method adds 280 days to the first day of your last period, assuming ovulation around day 14 of a textbook 28-day cycle, which places conception roughly two weeks after the LMP. If you instead know your conception or ovulation date, the EDD is calculated by adding 266 days, since that skips the two-week pre-ovulation window. Both routes land on the same delivery estimate for an average cycle, but the conception-based figure can be more accurate when your cycle differs from 28 days.

Treat the result as an estimate, not a deadline. Only about 5 percent of babies arrive on their exact calculated due date, while roughly 80 percent are born within two weeks either side of it, so a full-term birth anywhere from 37 to 42 weeks is entirely normal. A first-trimester ultrasound (typically weeks 8 to 13) measures the fetus directly and is considered the most accurate way to confirm or revise dating. On privacy: every calculation runs entirely in your browser. Your last period or conception date is never uploaded, stored, or shared, so nothing leaves your device.

Frequently asked questions

What information do I need to calculate my due date?

At minimum, the first day of your last menstrual period (LMP). If you know your conception or ovulation date instead, you can use that for a result that better fits an irregular cycle. No medical records or sign-up are required.

How accurate is a due date calculator?

It gives a reliable estimate but not a precise prediction. Only about 5 percent of babies are born on the exact due date, and around 80 percent arrive within two weeks before or after it. A first-trimester ultrasound is the most accurate way to confirm the date.

Why does the calculator count from my last period instead of conception?

Most people know the date their last period started, but few can pinpoint the exact day of conception. Naegele's rule counts 280 days from the LMP and assumes conception occurred about 14 days later, which makes the estimate practical without needing a known conception date.

What if my menstrual cycle is irregular or not 28 days long?

The LMP method assumes a 28-day cycle with ovulation on day 14, so a longer or shorter cycle can shift your true due date. If your cycle is irregular, use a known conception or ovulation date for a closer estimate, and rely on an early ultrasound for confirmation.

Can I use this calculator if my pregnancy resulted from IVF?

Yes. With IVF the conception timing is known precisely, so a conception-based calculation is more exact. Add 266 days to the conception (transfer) date, or adjust for the embryo's age, and confirm the result with your fertility clinic.

From our blog

Steps Per Mile, Explained: Why Your Height and Pace Change the Number

By the Super Simple Digital Tools Team · Updated June 2026

If you have ever seen the claim that a mile equals 2,000 steps, it is a useful starting point but rarely your actual number. Step count per mile depends almost entirely on stride length, and stride length varies with your height, your pace, and even whether you are walking or running. The same mile can range from under 1,500 steps for a tall runner to over 2,500 for a shorter person on a slow stroll. A calculator helps because it replaces that single rounded figure with a number tailored to how you actually move.

The underlying math is straightforward. A mile is 63,360 inches, so dividing that by your stride length in inches gives steps per mile, and multiplying steps by stride length then dividing by 63,360 converts back to distance. Everything else, from height shortcuts to pace tables, is just a way of estimating that one stride-length input. Once you understand this, you can see why a longer stride always means fewer steps for the same distance, and why your personal number is worth nailing down.

Pace matters more than most people expect. Research summarized from a 2008 ACSM study shows roughly 2,250 steps for an average 3 mph walk, about 2,000 for a brisk 4 mph walk, and near 1,700 steps for a 6 mph run. As you accelerate, you push off harder and reach farther, lengthening each stride. That is why fitness trackers sometimes seem to undercount your runs compared to your walks: you are genuinely taking fewer, bigger steps to cover the ground.

Height gives you a quick estimate when you cannot measure. Multiplying height in inches by about 0.413 (women) or 0.415 (men) approximates walking stride length, which you can then feed into the mile formula. This works because taller people generally have longer legs and longer strides. But it is only an approximation; leg-to-torso ratio, flexibility, and walking style all shift the real value, so treat height-based numbers as a ballpark rather than gospel.

The most reliable approach is to measure yourself once. Mark a start line, take ten natural steps, measure the distance to your final heel strike, and divide by ten. Do it separately for walking and running, since the two strides differ. With those two personal stride lengths saved, this calculator becomes a precise tool for planning routes, hitting step goals, and translating any tracked distance into a step count you can trust.

  • Measure separate stride lengths for walking and running; using one value for both will skew whichever activity it does not match.
  • When using the height shortcut, multiply inches by 0.413 for women or 0.415 for men, then refine it later with a real measurement.
  • To plan a 10,000-step day, divide 10,000 by your steps-per-mile to see the mileage you actually need to cover.
  • If your tracker and this calculator disagree, recheck your stride input first, since a half-inch error compounds across thousands of steps.

Read the full guide →

Tool by the Super Simple Digital Tools Team. Reviewed by our editorial team. Free to use, no signup required.

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