pregnancy and due date calculator

How this pregnancy and due date calculator works

This tool estimates your expected delivery date (EDD) using common clinical formulas. Most pregnancies are tracked as 40 weeks (280 days) from the first day of your last menstrual period, not from conception day. If you know conception or IVF transfer timing, we can estimate from those data points too.

Because every pregnancy is unique, this date is an estimate—not a guarantee. Many babies arrive before or after the due date, and that can still be completely normal.

Methods included in this calculator

• LMP method: Adds 280 days to the first day of your last period, then adjusts for your cycle length.
• Conception method: Adds 266 days from conception date.
• IVF method: Uses transfer date plus embryo age to estimate equivalent gestational dating.

What is gestational age?

Gestational age is the standard timeline used in prenatal care. It starts on day 1 of your last period, even though actual fertilization usually happens about two weeks later in a typical cycle.

This is why someone can be called “4 weeks pregnant” even if conception happened around 2 weeks ago. Clinics and ultrasound reports use this same dating framework, which keeps everyone on the same timeline.

Why due dates can change

It is common for the estimated due date to shift slightly after your first-trimester ultrasound. Early ultrasound measurements can be more precise than menstrual dating, especially if periods are irregular.

Factors that can affect due date estimates

• Irregular or unpredictable menstrual cycles
• Not being sure of the LMP date
• Late ovulation or implantation
• Assisted reproduction timing details
• Dating updates based on early ultrasound

Trimester overview

First trimester (weeks 1–13)

Rapid organ development begins. Common symptoms include fatigue, nausea, breast tenderness, and frequent urination. Early prenatal visits often include bloodwork and initial screening discussions.

Second trimester (weeks 14–27)

Many people feel more energy during this stage. Anatomy scan ultrasound is commonly performed around week 20. Movement (“quickening”) is often felt during this trimester.

Third trimester (weeks 28–40)

Growth accelerates and prenatal visits become more frequent. You may discuss labor signs, birth planning, and postpartum support. Babies born from 39 weeks onward are generally considered full term.

How to use your result

Your result includes:

• Estimated due date
• Current gestational age in weeks and days
• Current trimester
• Days remaining until due date
• A timeline of key milestones

Use these dates for planning appointments, leave windows, baby prep, and milestone tracking. Always confirm important medical decisions with your OB-GYN, midwife, or fertility specialist.

Frequently asked questions

Is this tool accurate?

It uses standard formulas used worldwide for initial estimates. Still, ultrasound and your provider’s clinical assessment are more definitive when dating uncertainty exists.

If my cycle is not 28 days, does that matter?

Yes. A longer cycle may shift ovulation later and due date later. A shorter cycle may shift earlier. That’s why the calculator lets you enter average cycle length.

Can I calculate due date before pregnancy is confirmed?

You can estimate dates for planning purposes, but actual pregnancy dating should be confirmed after a positive test and a clinical visit.

Important safety note

This calculator is for education and planning only. It is not a diagnosis tool and does not replace professional care. Seek urgent medical care for severe pain, heavy bleeding, fever, fainting, or any concerning symptoms during pregnancy.