Find your baby's due date, current week, and trimester — free and instant.
When you calculate from your last menstrual period, gestational age is counted from the first day of that period. The result above shows your estimated weeks pregnant and trimester alongside the due date. If your dates are uncertain, your cycles are irregular, or an ultrasound gives different dating, follow the estimate confirmed by your healthcare provider.
The standard LMP method estimates the due date at 280 days (40 weeks) from the first day of the last menstrual period for a regular 28-day cycle. For regular cycles of a different length, this calculator adjusts the estimate by the difference between your cycle length and 28 days.
If you know your conception date, the calculator adds 266 days (38 weeks). Conception dates can be difficult to know precisely unless timing is medically established.
An estimated due date is a guide, not a guaranteed delivery date. ACOG notes that only about 1 in 20 women give birth on their exact due date, and first-trimester ultrasound is the most accurate method to establish or confirm gestational age.
QuickAgeCalc uses standard calendar formulas for an initial estimate:
ACOG: Methods for Estimating the Due Date explains that first-trimester ultrasound is the most accurate method to establish or confirm gestational age and that assisted-reproduction pregnancies should use ART-specific dating.
Merck Manual: Estimated Date of Delivery gives the cycle-adjusted formula used here. The NHS due date guidance also notes that cycle length can affect the estimate and that an antenatal scan can provide more accurate dating.
Important: This calculator is for general information and is not a substitute for prenatal care. IVF and other assisted-reproduction pregnancies require method-specific dating by the treating clinician.