Pregnancy Timeline
| Milestone | Week |
|---|---|
| First trimester ends | Week 13 |
| Second trimester ends | Week 27 |
| Anatomy ultrasound | Week 18–20 |
| Viability milestone | Week 24 |
| Full term begins | Week 39 |
| Due date (40 weeks) | Week 40 |
Due Date Calculator
Estimate your pregnancy due date based on your last menstrual period (LMP) or conception date. See your current trimester, week of pregnancy, and key milestone dates.
Pregnancy Due Date
Frequently Asked Questions
How is the due date calculated?
The most common method is Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle with ovulation on day 14. For cycles different from 28 days, the calculator adjusts accordingly. Only about 5% of babies arrive on their exact due date — most arrive within 2 weeks either side.
When do the trimesters start and end?
The first trimester runs from week 1 through week 13 (weeks 1–13). The second trimester covers weeks 14 through 27. The third trimester goes from week 28 until birth. Full term is considered 39–40 weeks. Babies born before 37 weeks are considered preterm.
How Date and Time Calculations Work
Calculating time differences, work hours, and date intervals requires handling the non-uniform nature of calendars — months have 28–31 days, leap years add a day, and daylight saving time shifts clocks by an hour. This calculator handles those complexities automatically so you get accurate results every time.
Common Time Calculation Formulas
- Time difference: Convert both times to total minutes from midnight, subtract, convert back
- Weekly work hours: Sum of daily hours; overtime typically kicks in above 8 hours/day or 40 hours/week (varies by state)
- Days between dates: Count calendar days inclusive or exclusive of start/end depending on context
- Business days: Subtract weekends and federal holidays from total calendar days
How to Use This Calculator
- Enter your start and end times or dates in the provided fields
- For work hours, enter daily clock-in and clock-out times for each day
- Include any unpaid break times to get accurate paid hours
- Click Calculate to see total hours, days, or the breakdown you need
Overtime Rules in the US
Under the Fair Labor Standards Act (FLSA), non-exempt employees must be paid 1.5× their regular rate for all hours over 40 in a workweek. Some states (California, Nevada, Alaska) have daily overtime rules — 1.5× after 8 hours in a single day. Always check your state labor law for the specific rules that apply to your situation.
Example: Weekly Timesheet
Mon–Fri: 8:00 AM – 5:00 PM with 30-min unpaid lunch = 8.5 hrs/day × 5 = 42.5 hours
Regular pay (40 hrs): 40 × hourly rate | Overtime (2.5 hrs): 2.5 × 1.5 × hourly rate