Baby Size Dog Breed worksheet

1. Closest dog breed by weight: A Chihuahua

1. A due date is 280 days after the first day of the last period, so count back 280 days to find that starting day

   $\text{Mar 4, 2026}\text{−}280\text{\hspace{0.17em}days}$$=\text{May 28, 2025}$

2. Count the days from the first day of the last period to the counting-from date

   $\text{Jan 6, 2026}\text{−}\text{May 28, 2025}$$=223\text{\hspace{0.17em}days}$

3. Split the days into whole weeks and leftover days, since pregnancy is counted in weeks

   $223\text{÷ 7}$$=\text{31 weeks, 6 days}$

4. Put week 31 into the Hadlock formula for typical weight. The answer is the natural log (ln) of the weight in grams

   $0.578\text{+}0.332\text{×}31-0.00354\text{×}31\text{²}$$=7.4681$

5. Undo the log by raising e (about 2.718) to that power, then round to the nearest gram

   $e^{7.4681}$$=\mathrm{1,751}\text{\hspace{0.17em}g}$

6. Find the dog breed nearest in weight, a Chihuahua. Divide the baby's typical weight by its weight to compare them

   $\frac{\mathrm{1,751}\text{\hspace{0.17em}g}}{\mathrm{2,000}\text{\hspace{0.17em}g}}$$=0.88$

7. The ratio is between 0.67 and 1.5, so the two weigh about the same. That makes it a fair match

   $0.88\text{is within 1.5 times either way →}\text{A Chihuahua}$

2. Closest dog breed by weight: No close match this week

1. Put week 24 into the Hadlock formula for typical weight. The answer is the natural log (ln) of the weight in grams

   $0.578\text{+}0.332\text{×}24-0.00354\text{×}24\text{²}$$=6.507$

2. Undo the log by raising e (about 2.718) to that power, then round to the nearest gram

   $e^{6.507}$$=670\text{\hspace{0.17em}g}$

3. Find the dog breed nearest in weight, a Chihuahua. Divide the baby's typical weight by its weight to compare them

   $\frac{670\text{\hspace{0.17em}g}}{\mathrm{2,000}\text{\hspace{0.17em}g}}$$=0.34$

4. The ratio is outside 0.67 to 1.5, so even the nearest dog breed is not a fair match

   $0.34\text{is more than 1.5 times off →}\text{No close match this week}$

3. Closest dog breed by weight: No close match this week

1. Put week 16 into the Hadlock formula for typical weight. The answer is the natural log (ln) of the weight in grams

   $0.578\text{+}0.332\text{×}16-0.00354\text{×}16\text{²}$$=4.9838$

2. Undo the log by raising e (about 2.718) to that power, then round to the nearest gram

   $e^{4.9838}$$=146\text{\hspace{0.17em}g}$

3. Find the dog breed nearest in weight, a Chihuahua. Divide the baby's typical weight by its weight to compare them

   $\frac{146\text{\hspace{0.17em}g}}{\mathrm{2,000}\text{\hspace{0.17em}g}}$$=0.07$

4. The ratio is outside 0.67 to 1.5, so even the nearest dog breed is not a fair match

   $0.07\text{is more than 1.5 times off →}\text{No close match this week}$

4. Closest dog breed by weight: No close match this week

1. A due date is 280 days after the first day of the last period, so count back 280 days to find that starting day

   $\text{Oct 20, 2025}\text{−}280\text{\hspace{0.17em}days}$$=\text{Jan 13, 2025}$

2. Count the days from the first day of the last period to the counting-from date

   $\text{May 13, 2025}\text{−}\text{Jan 13, 2025}$$=120\text{\hspace{0.17em}days}$

3. Split the days into whole weeks and leftover days, since pregnancy is counted in weeks

   $120\text{÷ 7}$$=\text{17 weeks, 1 day}$

4. Put week 17 into the Hadlock formula for typical weight. The answer is the natural log (ln) of the weight in grams

   $0.578\text{+}0.332\text{×}17-0.00354\text{×}17\text{²}$$=5.1989$

5. Undo the log by raising e (about 2.718) to that power, then round to the nearest gram

   $e^{5.1989}$$=181\text{\hspace{0.17em}g}$

6. Find the dog breed nearest in weight, a Chihuahua. Divide the baby's typical weight by its weight to compare them

   $\frac{181\text{\hspace{0.17em}g}}{\mathrm{2,000}\text{\hspace{0.17em}g}}$$=0.09$

7. The ratio is outside 0.67 to 1.5, so even the nearest dog breed is not a fair match

   $0.09\text{is more than 1.5 times off →}\text{No close match this week}$

5. Closest dog breed by weight: A Chihuahua

1. Put week 32 into the Hadlock formula for typical weight. The answer is the natural log (ln) of the weight in grams

   $0.578\text{+}0.332\text{×}32-0.00354\text{×}32\text{²}$$=7.577$

2. Undo the log by raising e (about 2.718) to that power, then round to the nearest gram

   $e^{7.577}$$=\mathrm{1,953}\text{\hspace{0.17em}g}$

3. Find the dog breed nearest in weight, a Chihuahua. Divide the baby's typical weight by its weight to compare them

   $\frac{\mathrm{1,953}\text{\hspace{0.17em}g}}{\mathrm{2,000}\text{\hspace{0.17em}g}}$$=0.98$

4. The ratio is between 0.67 and 1.5, so the two weigh about the same. That makes it a fair match

   $0.98\text{is within 1.5 times either way →}\text{A Chihuahua}$

6. Closest dog breed by weight: No close match this week

1. Put week 20 into the Hadlock formula for typical weight. The answer is the natural log (ln) of the weight in grams

   $0.578\text{+}0.332\text{×}20-0.00354\text{×}20\text{²}$$=5.802$

2. Undo the log by raising e (about 2.718) to that power, then round to the nearest gram

   $e^{5.802}$$=331\text{\hspace{0.17em}g}$

3. Find the dog breed nearest in weight, a Chihuahua. Divide the baby's typical weight by its weight to compare them

   $\frac{331\text{\hspace{0.17em}g}}{\mathrm{2,000}\text{\hspace{0.17em}g}}$$=0.17$

4. The ratio is outside 0.67 to 1.5, so even the nearest dog breed is not a fair match

   $0.17\text{is more than 1.5 times off →}\text{No close match this week}$

7. Closest dog breed by weight: No close match this week

1. Count the days from the first day of the last period to the counting-from date

   $\text{Apr 12, 2025}\text{−}\text{Jan 11, 2025}$$=91\text{\hspace{0.17em}days}$

2. Split the days into whole weeks and leftover days, since pregnancy is counted in weeks

   $91\text{÷ 7}$$=\text{13 weeks, 0 days}$

3. Put week 13 into the Hadlock formula for typical weight. The answer is the natural log (ln) of the weight in grams

   $0.578\text{+}0.332\text{×}13-0.00354\text{×}13\text{²}$$=4.2957$

4. Undo the log by raising e (about 2.718) to that power, then round to the nearest gram

   $e^{4.2957}$$=73\text{\hspace{0.17em}g}$

5. Find the dog breed nearest in weight, a Chihuahua. Divide the baby's typical weight by its weight to compare them

   $\frac{73\text{\hspace{0.17em}g}}{\mathrm{2,000}\text{\hspace{0.17em}g}}$$=0.04$

6. The ratio is outside 0.67 to 1.5, so even the nearest dog breed is not a fair match

   $0.04\text{is more than 1.5 times off →}\text{No close match this week}$

8. Closest dog breed by weight: No close match this week

1. Put week 12 into the Hadlock formula for typical weight. The answer is the natural log (ln) of the weight in grams

   $0.578\text{+}0.332\text{×}12-0.00354\text{×}12\text{²}$$=4.0522$

2. Undo the log by raising e (about 2.718) to that power, then round to the nearest gram

   $e^{4.0522}$$=58\text{\hspace{0.17em}g}$

3. Find the dog breed nearest in weight, a Chihuahua. Divide the baby's typical weight by its weight to compare them

   $\frac{58\text{\hspace{0.17em}g}}{\mathrm{2,000}\text{\hspace{0.17em}g}}$$=0.03$

4. The ratio is outside 0.67 to 1.5, so even the nearest dog breed is not a fair match

   $0.03\text{is more than 1.5 times off →}\text{No close match this week}$

9. Closest dog breed by weight: A Maltese

1. A due date is 280 days after the first day of the last period, so count back 280 days to find that starting day

   $\text{Jan 2, 2027}\text{−}280\text{\hspace{0.17em}days}$$=\text{Mar 28, 2026}$

2. Count the days from the first day of the last period to the counting-from date

   $\text{Dec 28, 2026}\text{−}\text{Mar 28, 2026}$$=275\text{\hspace{0.17em}days}$

3. Split the days into whole weeks and leftover days, since pregnancy is counted in weeks

   $275\text{÷ 7}$$=\text{39 weeks, 2 days}$

4. Put week 39 into the Hadlock formula for typical weight. The answer is the natural log (ln) of the weight in grams

   $0.578\text{+}0.332\text{×}39-0.00354\text{×}39\text{²}$$=8.1417$

5. Undo the log by raising e (about 2.718) to that power, then round to the nearest gram

   $e^{8.1417}$$=\mathrm{3,435}\text{\hspace{0.17em}g}$

6. Find the dog breed nearest in weight, a Maltese. Divide the baby's typical weight by its weight to compare them

   $\frac{\mathrm{3,435}\text{\hspace{0.17em}g}}{\mathrm{3,500}\text{\hspace{0.17em}g}}$$=0.98$

7. The ratio is between 0.67 and 1.5, so the two weigh about the same. That makes it a fair match

   $0.98\text{is within 1.5 times either way →}\text{A Maltese}$

10. Closest dog breed by weight: No close match this week

1. A due date is 280 days after the first day of the last period, so count back 280 days to find that starting day

   $\text{Oct 23, 2025}\text{−}280\text{\hspace{0.17em}days}$$=\text{Jan 16, 2025}$

2. Count the days from the first day of the last period to the counting-from date

   $\text{Apr 5, 2025}\text{−}\text{Jan 16, 2025}$$=79\text{\hspace{0.17em}days}$

3. Split the days into whole weeks and leftover days, since pregnancy is counted in weeks

   $79\text{÷ 7}$$=\text{11 weeks, 2 days}$

4. Put week 11 into the Hadlock formula for typical weight. The answer is the natural log (ln) of the weight in grams

   $0.578\text{+}0.332\text{×}11-0.00354\text{×}11\text{²}$$=3.8017$

5. Undo the log by raising e (about 2.718) to that power, then round to the nearest gram

   $e^{3.8017}$$=45\text{\hspace{0.17em}g}$

6. Find the dog breed nearest in weight, a Chihuahua. Divide the baby's typical weight by its weight to compare them

   $\frac{45\text{\hspace{0.17em}g}}{\mathrm{2,000}\text{\hspace{0.17em}g}}$$=0.02$

7. The ratio is outside 0.67 to 1.5, so even the nearest dog breed is not a fair match

   $0.02\text{is more than 1.5 times off →}\text{No close match this week}$