Method 1: from your last period
- Find the first day of your last period.
- Count the days from then until today.
- Divide by 7. The whole number is weeks; the remainder is days.
Example: LMP on 1 June, today is 20 August. That’s 80 days → 80 ÷ 7 = 11 remainder 3 → 11 weeks 3 days pregnant.
Method 2: from your due date
Count the days from today until your due date and subtract from 280. If your due date is 90 days away, you are 280 − 90 = 190 days → 27 weeks 1 day.
Method 3: from a scan report
A scan report states gestational age on the day of the scan, for example “GA 8w 2d”. Add the weeks and days since the scan. Scan on 5 March showing 8w 2d; today is 26 March (21 days = 3 weeks) → 11 weeks 2 days.
Let the pregnancy week calculator do all three methods for you – including cycle-length adjustment.
Quick lookup: time since LMP
| Time since LMP | Weeks pregnant | Month |
|---|---|---|
| 1 month (≈30 days) | 4w 2d | 1 |
| 2 months (≈61 days) | 8w 5d | 2 |
| 3 months (≈91 days) | 13w 0d | 3 |
| 4 months (≈122 days) | 17w 3d | 4 |
| 5 months (≈152 days) | 21w 5d | 5 |
| 6 months (≈183 days) | 26w 1d | 6 |
| 7 months (≈213 days) | 30w 3d | 7 |
| 8 months (≈244 days) | 34w 6d | 8 |
| 9 months (≈274 days) | 39w 1d | 9 |
Common mix-ups
- Counting from conception: this makes you appear two weeks less pregnant than your doctor’s dates.
- Using the last day of the period: always use the first day.
- Confusing “in week 12” with “12 weeks”: at 12 weeks 3 days you are in your 13th week.
Frequently asked questions
How many weeks pregnant am I if I missed my period yesterday?
About 4 weeks, assuming a regular 28-day cycle.
How do doctors know how many weeks pregnant I am?
They count from your last period and confirm with an ultrasound, ideally in the first trimester.
Medical disclaimer: The results and information on this page are estimates for general education only. They are not a diagnosis and do not replace advice from your gynaecologist, obstetrician or midwife. If you have pain, bleeding, reduced baby movements or feel unwell, contact your doctor or call 108 immediately. Read the full disclaimer.