Find out what week and day of pregnancy you're currently in, and which trimester, starting from either your last menstrual period or an already-known due date.
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Pregnancy is conventionally tracked from the first day of your last menstrual period (LMP), even though conception happens roughly two weeks later, this is the standard medical convention. If you know your LMP date, this calculator adds 280 days (40 weeks) to estimate your due date. If instead you only know your due date, perhaps given by a doctor or from an ultrasound, this calculator works backward, subtracting 280 days to estimate your LMP, then calculates your current week, day and trimester the same way either way.
This calculator is focused on 'what week am I in right now', supporting either an LMP or due date starting point. Our Pregnancy Due Date Calculator only accepts an LMP date directly. Our Due Date Reverse Calculator, meanwhile, is a pure reference tool: given a due date, it reconstructs your estimated LMP, conception date and trimester start dates without referencing today's date at all, useful for looking up your full timeline rather than tracking current progress.
For example, if exactly 143 days (20 weeks and 3 days) have passed since the first day of your last menstrual period, you're in week 20, day 3, in your second trimester (which starts at week 14), with about 20 weeks remaining until your estimated due date, 280 days after your LMP.
Entering the due date when the tool's LMP mode is still selected (or vice versa), the mode toggle changes what the date field means, and mismatching them shifts every downstream result by up to a couple of weeks.
Treating 'weeks remaining' as a countdown to a guaranteed delivery date, most healthy pregnancies deliver anywhere from 37 to 42 weeks, not precisely at 40.
Assuming trimester boundaries are universally agreed upon, some sources define them slightly differently (for example by month rather than week), so a week or two of difference near a boundary is normal.
Not everyone tracks their exact LMP date precisely, or your due date may have been adjusted by an early ultrasound, which is often considered more accurate than LMP-based dating alone. Entering your known due date directly lets you skip needing an exact LMP date.
It's an approximation based on a standard 40-week (280-day) full term. Actual delivery timing varies, most healthy pregnancies deliver somewhere between 37 and 42 weeks.
This calculator uses the common convention of weeks 1-13 as the first trimester, 14-26 as the second, and 27 onward as the third, though exact boundaries are sometimes defined slightly differently between sources.
Due Date Reverse Calculator
Work backward from a due date to estimate your LMP, conception date and trimester start dates.
Pregnancy Weight Gain Calculator
See the recommended pregnancy weight gain range based on your pre-pregnancy BMI.
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