Conception Date worksheet

1. Estimated conception date: Thursday, Nov 7, 2024

1. Ovulation is usually about 14 days before your next period. So take 14 from your cycle length

   $14+\left(38-28\right)$$=38-14$$=24\text{\hspace{0.17em}days}$

2. Count that many days on from the first day of your last period

   $\text{Oct 14, 2024}\text{+}24\text{\hspace{0.17em}days}$$=\text{Thursday, Nov 7, 2024}$

3. Add 266 days to that to find the matching due date

   $\text{Nov 7, 2024}\text{+}266\text{\hspace{0.17em}days}$$=\text{Thursday, Jul 31, 2025}$

4. Add 3 days on each side for a likely window, since the exact day can't be known

   $\text{Nov 7, 2024}\text{±}3\text{\hspace{0.17em}days}$$=\text{Nov 4, 2024 to Nov 10, 2024}$

2. Estimated conception date: Friday, Nov 14, 2025

1. Ovulation is usually about 14 days before your next period. So take 14 from your cycle length

   $14+\left(21-28\right)$$=21-14$$=7\text{\hspace{0.17em}days}$

2. Count that many days on from the first day of your last period

   $\text{Nov 7, 2025}\text{+}7\text{\hspace{0.17em}days}$$=\text{Friday, Nov 14, 2025}$

3. Add 266 days to that to find the matching due date

   $\text{Nov 14, 2025}\text{+}266\text{\hspace{0.17em}days}$$=\text{Friday, Aug 7, 2026}$

4. Add 2 days on each side for a likely window, since the exact day can't be known

   $\text{Nov 14, 2025}\text{±}2\text{\hspace{0.17em}days}$$=\text{Nov 12, 2025 to Nov 16, 2025}$

3. Estimated conception date: Friday, Jan 17, 2025

1. A due date is 280 days after the last period. Conception is about 14 days in, so it's 266 days before the due date

   $280-14$$=266\text{\hspace{0.17em}days}$

2. Count back 266 days from the due date

   $\text{Oct 10, 2025}\text{−}266\text{\hspace{0.17em}days}$$=\text{Friday, Jan 17, 2025}$

3. Add 3 days on each side for a likely window, since the exact day can't be known

   $\text{Jan 17, 2025}\text{±}3\text{\hspace{0.17em}days}$$=\text{Jan 14, 2025 to Jan 20, 2025}$

4. Estimated conception date: Tuesday, Jan 28, 2025

1. A due date is 280 days after the last period. Conception is about 14 days in, so it's 266 days before the due date

   $280-14$$=266\text{\hspace{0.17em}days}$

2. Count back 266 days from the due date

   $\text{Oct 21, 2025}\text{−}266\text{\hspace{0.17em}days}$$=\text{Tuesday, Jan 28, 2025}$

3. Add 4 days on each side for a likely window, since the exact day can't be known

   $\text{Jan 28, 2025}\text{±}4\text{\hspace{0.17em}days}$$=\text{Jan 24, 2025 to Feb 1, 2025}$

5. Estimated due date: Saturday, Jul 18, 2026

1. Pregnancy is counted as 280 days from the last period. Conception is about 14 days in, which leaves 266 days

   $280-14$$=266\text{\hspace{0.17em}days}$

2. Add those 266 days to the conception date to reach the due date

   $\text{Oct 25, 2025}\text{+}266\text{\hspace{0.17em}days}$$=\text{Saturday, Jul 18, 2026}$

3. Count back 14 days to find the start date that pregnancy weeks are counted from

   $\text{Oct 25, 2025}\text{−}14\text{\hspace{0.17em}days}$$=\text{Oct 11, 2025}$

6. Estimated due date: Friday, Sep 24, 2027

1. Pregnancy is counted as 280 days from the last period. Conception is about 14 days in, which leaves 266 days

   $280-14$$=266\text{\hspace{0.17em}days}$

2. Add those 266 days to the conception date to reach the due date

   $\text{Jan 1, 2027}\text{+}266\text{\hspace{0.17em}days}$$=\text{Friday, Sep 24, 2027}$

3. Count back 14 days to find the start date that pregnancy weeks are counted from

   $\text{Jan 1, 2027}\text{−}14\text{\hspace{0.17em}days}$$=\text{Dec 18, 2026}$

7. Estimated conception date: Wednesday, Apr 15, 2026

1. A due date is 280 days after the last period. Conception is about 14 days in, so it's 266 days before the due date

   $280-14$$=266\text{\hspace{0.17em}days}$

2. Count back 266 days from the due date

   $\text{Jan 6, 2027}\text{−}266\text{\hspace{0.17em}days}$$=\text{Wednesday, Apr 15, 2026}$

3. Add 2 days on each side for a likely window, since the exact day can't be known

   $\text{Apr 15, 2026}\text{±}2\text{\hspace{0.17em}days}$$=\text{Apr 13, 2026 to Apr 17, 2026}$

8. Estimated conception date: Saturday, Mar 21, 2026

1. A due date is 280 days after the last period. Conception is about 14 days in, so it's 266 days before the due date

   $280-14$$=266\text{\hspace{0.17em}days}$

2. Count back 266 days from the due date

   $\text{Dec 12, 2026}\text{−}266\text{\hspace{0.17em}days}$$=\text{Saturday, Mar 21, 2026}$

3. Add 2 days on each side for a likely window, since the exact day can't be known

   $\text{Mar 21, 2026}\text{±}2\text{\hspace{0.17em}days}$$=\text{Mar 19, 2026 to Mar 23, 2026}$

9. Estimated conception date: Wednesday, Sep 23, 2026

1. Ovulation is usually about 14 days before your next period. So take 14 from your cycle length

   $14+\left(32-28\right)$$=32-14$$=18\text{\hspace{0.17em}days}$

2. Count that many days on from the first day of your last period

   $\text{Sep 5, 2026}\text{+}18\text{\hspace{0.17em}days}$$=\text{Wednesday, Sep 23, 2026}$

3. Add 266 days to that to find the matching due date

   $\text{Sep 23, 2026}\text{+}266\text{\hspace{0.17em}days}$$=\text{Wednesday, Jun 16, 2027}$

4. Add 4 days on each side for a likely window, since the exact day can't be known

   $\text{Sep 23, 2026}\text{±}4\text{\hspace{0.17em}days}$$=\text{Sep 19, 2026 to Sep 27, 2026}$

10. Estimated due date: Sunday, Jul 25, 2027

1. Pregnancy is counted as 280 days from the last period. Conception is about 14 days in, which leaves 266 days

   $280-14$$=266\text{\hspace{0.17em}days}$

2. Add those 266 days to the conception date to reach the due date

   $\text{Nov 1, 2026}\text{+}266\text{\hspace{0.17em}days}$$=\text{Sunday, Jul 25, 2027}$

3. Count back 14 days to find the start date that pregnancy weeks are counted from

   $\text{Nov 1, 2026}\text{−}14\text{\hspace{0.17em}days}$$=\text{Oct 18, 2026}$