How the pregnancy due date from LMP is calculated
The standard pregnancy due date calculator adds 280 days to the first day of your last menstrual period using Naegele rule, which is equivalent to adding seven days, subtracting three months and adding one year. For example a pregnancy due date from LMP of 1 January lands near 8 October. This assumes a 28-day cycle with ovulation near day 14, so the ovulation calculator tracker back-estimates conception around LMP plus 14 days. If your cycle is longer or shorter, the fertility window predictor shifts ovulation to cycle length minus 14 days, and dating may move by a few days. An early due date ultrasound adjustment between weeks 8 and 12 measures crown-rump length and often replaces LMP dating when the difference exceeds five to seven days, because first-trimester growth is remarkably uniform.
Ovulation tracker, fertility window and conception date calculator
Ovulation usually occurs about 14 days before the next period, so a 28-day cycle ovulates near day 14 while a 32-day cycle ovulates near day 18. The fertile window spans roughly five days before ovulation plus the ovulation day itself, since sperm survive longer than the egg. Our fertility window predictor combines your LMP with cycle length to flag that six-day window, and the conception date calculator adds 266 days to estimated conception as a cross-check against the 280-day LMP result. Both should agree within a day or two for regular cycles. Irregular cycles need scan dating instead, because ovulation timing varies and no calendar method can recover it precisely.
Week by week pregnancy progress chart and trimester milestones
The week by week pregnancy progress chart above plots approximate length from week 1 through week 40, rising slowly in the first trimester and steeply after week 20. Trimester milestone calculator splits commonly run weeks 1 to 13 as first trimester, 14 to 27 as second, and 28 to 40 as third. Baby development week by week highlights include heartbeat near week 6, the end of the embryonic period near week 10, the nuchal scan window near weeks 11 to 13, the anatomy scan at 18 to 22 weeks, glucose screening at 24 to 28 weeks, and weekly visits from 36 weeks. The pregnancy calendar generator view in your PDF report lists these checkpoints beside your personal dates so antenatal appointments are easy to plan.
IVF due date tool, ultrasound adjustment and gestational age
IVF pregnancies skip LMP logic. A day-3 embryo transfer plus 263 days or a day-5 transfer plus 261 days approximates the due date, and the IVF due date tool note on the results card reminds you to confirm with your clinic. Ultrasound dating uses formula tables rather than calendar math, which is why the due date ultrasound adjustment can move your date even when LMP felt certain. Gestational age calculator output on this page always counts from LMP for consistency with clinic charts, while fetal age from conception runs about two weeks behind. If you know conception exactly, compare both numbers and carry the scan-confirmed date forward.
Pregnancy weight gain tracker context and test timing
The pregnancy weight gain tracker context follows common guidance of roughly 1 to 2 kilograms across the first trimester, then about 0.4 kilograms per week, adjusted by pre-pregnancy BMI and your doctor's advice. Gain is not linear and single weigh-ins matter less than the trend your history log draws. The best time to take a pregnancy test is after the missed period, around 14 days past ovulation, when urine hCG is reliably detectable. Earlier testing risks false negatives. Confirm any positive with a clinical test and book antenatal care promptly, bringing this page's PDF with your LMP, cycle length and milestone list.
Why track history and download the report
Your calculation history saves automatically in this browser under vc-history-pregnancy-calculator, so repeat visits show prior LMP entries and due dates without retyping. Charts render in your theme with reduced-motion respected, and the Download Full Pregnancy Report button embeds them as images alongside inputs, trimester splits and the medical disclaimer on every page. Competing pages from BabyCenter and WhatToExpect carry heavy ads and outdated layouts with no chart PDFs, while this tool stays fast, readable on phones with bottom tabs and large inputs, and fully static with nothing uploaded. Remember this tool is for educational purposes only and is not a substitute for professional medical advice. Always consult your doctor.