Health & Fitness
Pregnancy Week Calculator
Calculate current pregnancy week, trimester, and due date.
Formulas and edge cases are reviewed against authoritative references before publication. For methodology, editorial standards, or corrections, use the links below.
Frequently asked questions
How are pregnancy weeks counted?
From the first day of your last menstrual period, even though conception occurs ~2 weeks later.
Why adjust for cycle length?
Standard calculation assumes 28-day cycle. Longer/shorter cycles shift ovulation timing.
When does each trimester start?
First: weeks 1-12, Second: weeks 13-26, Third: weeks 27-40.
Related tools
About this tool
Inputs
- Last Menstrual Period
- Cycle Length
- week
- weeks
- day
- days
- Upcoming Milestones
- Week
- No upcoming milestones
Results
- Current Week
- Trimester
- Due Date
- Days Remaining
- First Trimester
- Second Trimester
- Third Trimester
Before making a decision based on estimates, run the numbers through this Pregnancy Week Calculator. A few seconds of input can save hours of uncertainty. Start by filling in last menstrual period, cycle length, week, weeks, day, days, upcoming milestones, week and no upcoming milestones. Based on these values, the tool computes current week, trimester, due date and other key metrics. Basal metabolic rate estimates use equations like Harris- Benedict or Mifflin-St Jeor, which factor in age, sex, height, and weight.
Reference ranges published by organizations like WHO and NIH apply to general adult populations and may not suit everyone. Measure consistently — same time of day, same conditions — for the most reliable comparisons. From students to professionals, anyone who needs to calculate current pregnancy week, trimester, and due date benefits from getting an instant, verifiable answer. Use the result as a starting point for deeper analysis. Pair it with other tools for a more complete picture. Athletes and pregnant individuals may fall outside standard reference ranges without any health concern.