Written by Dn. Aruba Rashid, certified dietitian (BS Human Nutrition and Dietetics). Updated October 2026.

How to Use the Pregnancy Calculator

Pick the option that matches what you know, enter the date and press the button. The calculator shows your due date, how many weeks and days pregnant you are, your trimester, and the dates of your main scans and tests.

• Last period: the most common way. Enter the first day of your last menstrual period (LMP) and your usual cycle length. If your cycle is longer or shorter than 28 days, the calculator adjusts your due date.
• Conception date: use this if you know the date you conceived.
• IVF transfer: enter your embryo transfer date and whether it was a day 3 or day 5 embryo.
• Ultrasound: enter the date of your scan and the weeks and days written on the report. A dating scan in the first trimester is the most accurate way to set a due date.

How Your Due Date Is Calculated

Doctors count pregnancy from the first day of your last period, not from the day you conceived. A full-term pregnancy is 280 days, or 40 weeks, from that date. This is known as Naegele’s rule: add 1 year, subtract 3 months and add 7 days to the first day of your last period.

For example, if your last period started on 1 July 2026, your due date is about 7 April 2027. When you calculate from conception, the calculator adds 266 days (38 weeks). For IVF, it adds 261 days to a day 5 transfer or 263 days to a day 3 transfer.

Pregnancy Weeks, Months and Trimesters

Pregnancy is split into three trimesters. Many families in Pakistan count in months, so here is how they line up:

Trimester	Weeks	Months	Extra calories a day
First	1 to 13	Months 1 to 3	None
Second	14 to 27	Months 4 to 6	About 340
Third	28 to 40	Months 7 to 9	About 450

Your due date is only an estimate. Only about 1 in 20 babies is born on the exact day. A baby born between 37 and 42 weeks is considered on time.

What to Eat in Each Trimester

Your diet matters as much as your scans. The idea of “eating for two” is a myth; you need a little more food, but a lot more nutrition.

• First trimester: no extra calories yet. Eat small meals every 2 to 3 hours to manage nausea, and take the folic acid your doctor prescribes.
• Second trimester: about 340 extra calories a day, such as a glass of milk, a banana and a handful of almonds. Focus on iron, calcium and protein.
• Third trimester: about 450 extra calories a day. Smaller meals help with heartburn, and less salt helps with swelling.

Our pregnancy diet plan has a full trimester-wise Pakistani diet chart, foods to avoid and common pregnancy food myths.

Key Scans and Tests During Pregnancy

The milestone table in the calculator shows when these usually happen for you. Your gynaecologist will decide exactly which ones you need.

• 6 to 8 weeks: first ultrasound to confirm the heartbeat and your dates.
• 11 to 14 weeks: NT scan and first trimester screening.
• 18 to 22 weeks: anatomy or anomaly scan to check your baby’s growth and organs.
• 24 to 28 weeks: sugar test (OGTT) for gestational diabetes, which is common in South Asian women.
• From 28 weeks: more frequent check-ups for blood pressure, baby’s growth and position.

If you are diagnosed with gestational diabetes, controlled portions of roti and rice and no sugary drinks make a big difference. Our diabetes diet chart explains the basics, but pregnancy needs a personal plan.

Healthy Weight Gain in Pregnancy

How much weight you should gain depends on your weight before pregnancy. Check your pre-pregnancy BMI with our BMI calculator, then use this guide:

BMI before pregnancy	Healthy total weight gain
Under 18.5 (underweight)	12.5 to 18 kg
18.5 to 24.9 (healthy)	11.5 to 16 kg
25 to 29.9 (overweight)	7 to 11.5 kg
30 or more (obese)	5 to 9 kg

These ranges are for one baby. If you are carrying twins, or gaining much faster or slower than this, speak to your doctor.

Frequently Asked Questions

How accurate is a pregnancy due date calculator?

It gives a good estimate if your cycle is regular and you remember the date of your last period. A first trimester ultrasound is more accurate, so your doctor may change your due date after your dating scan. Most babies arrive within two weeks either side of the due date.

How many weeks pregnant am I?

Count from the first day of your last period, not from when you conceived. Enter that date in the calculator above and it will show your exact weeks and days today.

Why does pregnancy count from my last period if I conceived 2 weeks later?

Most women know the date of their last period but not the exact day they conceived, so doctors use the period date as a fixed starting point. This is why you are already “2 weeks pregnant” on the day you conceive.

What if my periods are irregular?

The last period method is less reliable with irregular cycles, for example with PCOS. In that case, use the ultrasound option with the weeks and days from your first scan report.

How many months is 40 weeks of pregnancy?

40 weeks is about 9 months and 1 week. The first trimester ends at about 3 months, the second at about 6 months, and the third trimester runs to the end.

When should I first see a doctor?

Book your first visit as soon as you get a positive pregnancy test, ideally before 8 weeks. Start folic acid as early as possible if your doctor has not already prescribed it.

Get a Personal Pregnancy Diet Plan

Every pregnancy is different. Dn. Aruba Rashid, a certified dietitian, creates pregnancy diet plans around your trimester, weight, reports and family food, including plans for gestational diabetes and anaemia. She sees women in person in Multan and offers video sessions for women and WhatsApp consultations anywhere in Pakistan.