How pregnancy is dated, conception, hCG and weight gain.
Pregnancy is full of dates and milestones, and a little math makes them clearer. This guide explains how pregnancy is dated and what each calculator tells you. It's informational - your provider's dating and guidance always take precedence.
Pregnancy is counted from the first day of your last menstrual period (LMP), not from conception, which is why you're considered about two weeks 'pregnant' before conception actually occurs. A full term is roughly 280 days (40 weeks) from LMP. The Trimester Calculator shows your current week, trimester, due date and days remaining.
Conception usually happens around ovulation, about 14 days after the LMP in a typical cycle, or roughly 266 days before the due date. Because sperm can survive several days, conception falls in a window rather than on a single day. The Conception Date Calculator estimates your likely conception date and window from either a due date or your LMP.
In early pregnancy, the hormone hCG typically rises quickly, often roughly doubling every 48 to 72 hours, then slowing as levels climb. A single value means little; the trend across two tests is what providers watch. The hCG Doubling Time Calculator computes the doubling time and percent rise between two results.
Recommended pregnancy weight gain depends on your pre-pregnancy BMI, following the Institute of Medicine guidelines, with a different range for twins. The Pregnancy Weight Gain Calculator gives your recommended total and weekly gain. These are population guidelines; your provider tailors goals to your health.
Treat every result as an estimate. Cycle length varies, dating shifts after an early ultrasound, and individual pregnancies differ widely. The calculators are a way to understand the general timeline and ask better questions at appointments - not a substitute for prenatal care.
From the first day of your last menstrual period (LMP), about 280 days to the due date.
Roughly 14 days after your LMP, or about 266 days before your due date - within a small window.
Often it roughly doubles every 48 to 72 hours early on, but patterns vary.
It depends on your pre-pregnancy BMI; the calculator uses IOM guidelines.
No - they're estimates; your provider's guidance comes first.