HealthCalc Hub

Due date for a last period in January

Find your due date by month. This page covers a last period in January from day 1 to day 31 and shows where each date lands.

Pick a date to see your due date.

This calculator gives general information only. It is not medical advice. Talk to a doctor or other qualified health professional about your own health.

How it works

The due date is 280 days after the first day of the last period. That is 40 weeks from the last period. The January table has 31 rows, one per day.

Worked example

Say the first day of the last period is 15 January. Add 280 days to reach 22 October. Day 1 of January gives 8 October and day 31 gives 7 November. This example uses a 365-day year.

Estimated due date for each day of January, counting 280 days from the first day of the last period. The table uses a 365-day year.

First day of last periodDue date
1 January8 October
2 January9 October
3 January10 October
4 January11 October
5 January12 October
6 January13 October
7 January14 October
8 January15 October
9 January16 October
10 January17 October
11 January18 October
12 January19 October
13 January20 October
14 January21 October
15 January22 October
16 January23 October
17 January24 October
18 January25 October
19 January26 October
20 January27 October
21 January28 October
22 January29 October
23 January30 October
24 January31 October
25 January1 November
26 January2 November
27 January3 November
28 January4 November
29 January5 November
30 January6 November
31 January7 November

Common questions

How reliable is a due date worked out by month?

It is an estimate, and births spread across the weeks around it. A last period on day 15 of January gives 22 October, with arrivals spread across the weeks around that date.

Which month will my baby be born?

The due date month is a guide, and many births come earlier or later. A last period in January points to October and November.

What if I only know the month?

Use the middle of the month. The due date then falls in the middle of the window. Day 15 of January maps to 22 October.

How many weeks is the gap?

Divide the days by 7 to get weeks. From day 1 of January to 8 October is 280 days, which is 40 weeks.

What if my cycle is not regular?

When cycles are irregular, an ultrasound can date a pregnancy more reliably than a calendar. A date of 15 January would then give 22 October only as a first guess.