Pregnancy Calculator

Estimate your due date, current week of pregnancy, and trimester from your last menstrual period. Free, instant, no signup.

How to use the Pregnancy Calculator

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

Why use our Pregnancy Calculator

Instant results. Enter your figures and the pregnancy 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 Pregnancy Calculator

The Pregnancy Calculator estimates your due date and tells you how far along you are, expressed in weeks and days of gestation. By default it uses the first day of your last menstrual period (LMP) and applies Naegele's rule, the same method most obstetricians use: it adds 280 days (40 weeks) to your LMP to project an estimated delivery date. From that single date the tool works backwards and forwards to show your current gestational age, your trimester, your conception window, and a week-by-week timeline, so a few seconds of input turns one date into a full picture of where your pregnancy stands today.

Reach for this calculator the moment you want a clearer answer than "sometime around then." It is useful right after a positive test, when planning your first prenatal appointment, when booking a dating ultrasound, or simply when friends and family keep asking how many weeks you are. It also handles the cases where LMP is not the best anchor: if you tracked ovulation or know your conception date, you can count from there instead, and if you conceived through IVF the embryo transfer date gives the most precise estimate of all because the timing is known rather than inferred.

Under the hood the math is straightforward but worth understanding. Naegele's rule assumes a regular 28-day cycle with ovulation near day 14, so gestational age (counted from LMP) runs about two weeks ahead of the baby's actual fetal age (counted from conception). When you start from a conception or ovulation date instead, the tool counts forward roughly 266 days rather than 280. For IVF, it subtracts the embryo's age at transfer, using about 263 days for a day-3 transfer and 261 days for a day-5 blastocyst transfer, which keeps the timeline consistent with the standard gestational scale your provider uses.

Treat every result as a well-grounded estimate, not a fixed appointment. Studies show fewer than about 5% of babies arrive on their exact due date, while roughly 90% are born within two weeks either side, and an early first-trimester ultrasound (most accurate before 14 weeks via crown-rump length) remains the clinical gold standard for dating. If your cycle is longer, shorter, or irregular, the LMP estimate can drift by several days. On privacy: this calculator runs entirely in your browser, so the dates you enter are never uploaded, stored on a server, or shared with anyone.

Frequently asked questions

How does the calculator work out my due date?

By default it adds 280 days (40 weeks) to the first day of your last menstrual period, which is Naegele's rule. If you enter a conception or ovulation date instead, it counts forward about 266 days; for an IVF transfer it adjusts for the embryo's age (around 263 days for a day-3 transfer, 261 for a day-5 transfer).

How accurate is the estimated due date?

It is a solid estimate, not a guarantee. Fewer than about 5% of babies are born on their exact due date, and roughly 90% arrive within two weeks before or after it. An early first-trimester ultrasound is the most accurate way to confirm or adjust the date.

Why does it say I'm pregnant two weeks longer than I expected?

Pregnancy is measured from the first day of your last period, not from conception, so gestational age is about two weeks ahead of the baby's actual fetal age. At 10 weeks gestational age, for example, the embryo is roughly 8 weeks old.

What if my menstrual cycle isn't 28 days or is irregular?

Naegele's rule assumes a 28-day cycle with ovulation near day 14, so a longer or shorter cycle can shift the estimate by several days. If your cycle is irregular or you're unsure of your LMP, use your conception date or rely on a dating ultrasound for a firmer answer.

Can I use this if I conceived through IVF?

Yes, and it's often the most precise input because the transfer date is known. Enter your embryo transfer date and select the embryo's age; the calculator subtracts the transfer day from the standard 266-day count so the timeline matches the gestational scale your clinic uses.

From our blog

From Salary to Bank Account: How Your Paycheck Is Actually Built

By the Super Simple Digital Tools Team · Updated June 2026

When you accept a job at, say, $60,000 a year, that number never shows up in your account. Payroll runs your earnings through a fixed sequence of subtractions, and understanding that sequence is the difference between budgeting on a fantasy figure and budgeting on reality. The good news is the process is predictable. Once you know the order in which money is removed and why, a paycheck stops being a mystery and the estimate this calculator produces starts to make intuitive sense.

The first thing payroll does is convert your annual pay into a single period. Divide your salary by your number of pay dates: weekly gives 52 checks, biweekly 26, semimonthly 24, and monthly 12. Then come pre-tax deductions. Contributions to a traditional 401(k) and many health insurance premiums are pulled out before income tax is figured, which shrinks your taxable wages. This is why two people earning the same salary can owe different amounts of income tax: the one putting more into pre-tax benefits hands the IRS a smaller base to tax.

Next is federal income tax withholding, and this is where a common misconception trips people up. The United States uses graduated brackets, so only the dollars that fall inside a higher bracket are taxed at that higher rate, not your entire income. Your effective rate, the share of your pay that actually goes to federal tax, is therefore lower than your top bracket. The details you put on your W-4, such as filing status and dependents, tell your employer how much to hold back each period.

Then FICA takes its cut, and it works differently from income tax. Social Security is a flat 6.2% on wages up to an annual cap ($184,500 for 2026), after which it stops for the year. Medicare is 1.45% on every dollar with no cap, plus an additional 0.9% on wages above $200,000. Notably, FICA is charged on your 401(k) contributions even though income tax is not, so retirement savings shrink your income tax bill but not your Social Security and Medicare withholding.

Finally, state and local income taxes apply where they exist, and any after-tax deductions, such as Roth 401(k) contributions or wage garnishments, come off the end. What survives all of this is your net pay. Run your own numbers through the calculator, then compare the breakdown to a real pay stub. If they roughly line up, you can trust the tool for planning; if they do not, the gap usually points to a state tax, a benefit, or a W-4 setting worth a closer look.

  • Enter your pre-tax deductions like a traditional 401(k) and health premiums before reading the tax line, since they shrink the wages that income tax is calculated on.
  • Compare the same salary across weekly, biweekly, and monthly frequencies to see how check size changes even though your yearly take-home stays identical.
  • Remember that bumping up your 401(k) lowers income tax but not Social Security or Medicare, so the boost to take-home is smaller than the contribution amount.
  • Validate the estimate against an actual pay stub once; a large gap usually means a state or local tax or a benefit deduction that needs to be added.

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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