Pregnancy Week-by-Week Tracker

The calculator estimates your pregnancy week based on standard medical guidelines. If you use your last menstrual period (LMP), it assumes a 28-day cycle with ovulation on day 14. If you use your due date, it calculates backwards 280 days (40 weeks) from that date.

For the most accurate dating, consult with your healthcare provider who may use ultrasound measurements.

LMP (Last Menstrual Period) calculation uses the first day of your last period and adds 280 days (40 weeks) to estimate your due date.

Due Date calculation works backward from your known due date to determine your current week.

Most healthcare providers use LMP for initial dating, but may adjust based on ultrasound measurements.

Different calculators may use different methods:

• Some use 266 days from conception instead of 280 from LMP
• Some account for average cycle length variations
• Some include conception date if known

This calculator follows the standard Naegele's rule (LMP + 280 days) used by most healthcare providers.

You can check weekly for updates! The information changes each week as your baby develops. Many expectant parents enjoy:

• Weekly check-ins to see baby's size
• Monthly milestone reviews
• Setting reminders for important appointments
• Tracking symptoms week by week

The size comparisons are general estimates based on average fetal measurements. Every baby grows at their own pace, and actual size can vary due to:

• Genetics
• Nutrition
• Multiple pregnancies
• Medical conditions

The comparisons help visualize growth but should not be used for medical diagnosis.

If you're unsure about dates:

• Estimate your LMP: Try to remember the start date of your last period
• Use conception date: If you know when you conceived, add 266 days for due date
• Early ultrasound: First-trimester ultrasounds provide the most accurate dating
• Consult your doctor: They can help establish accurate dates

This tracker provides general pregnancy information that applies to all pregnancies. However, with twins or multiples:

• Babies may measure differently in size
• Development milestones may vary
• Due dates are often earlier (around 37 weeks)
• You'll have more frequent check-ups

Always follow your healthcare provider's specific guidance for multiple pregnancies.

Pregnancy is divided into three trimesters:

Always trust your healthcare provider's dating over online calculators. Differences can occur because:

• Ultrasound measurements may adjust dates
• Irregular menstrual cycles affect LMP calculation
• Late ovulation can shift dates
• Provider may use different calculation methods

This tool is for educational purposes and entertainment, not medical diagnosis.

You can track your pregnancy using our tools:

• Download weekly summaries for your records
• Set up email reminders for weekly updates
• Bookmark this page with your dates entered
• Take screenshots of important weeks
• Share updates with family and friends

For comprehensive tracking, consider using a pregnancy app alongside this tool.