Baby Size by Week worksheet

1. Typical weight at 31 weeks: 1,751 g

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. Divide by 28.35 to change grams to ounces, since an ounce is about 28.35 grams

   $\mathrm{1,751}\text{÷}28.35$$=61.8\text{\hspace{0.17em}oz}$

7. Take away last week's typical weight to see how much was gained over week 31

   $\mathrm{1,751}-\mathrm{1,559}$$=192\text{\hspace{0.17em}g}$

8. Take this week's weight from next week's to see the typical gain in the week ahead

   $\mathrm{1,953}-\mathrm{1,751}$$=202\text{\hspace{0.17em}g}$

9. Compare with the everyday item closest in weight, a 3-pound bag of apples, by dividing one weight by the other

   $\frac{\mathrm{1,751}\text{\hspace{0.17em}g}}{\mathrm{1,360.8}\text{\hspace{0.17em}g}}$$=1.29$

10. Take the days so far from the 280 days of a full-length pregnancy to find the time left

    $280-223$$=57\text{\hspace{0.17em}days}$

2. Typical weight at 24 weeks: 670 g

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. Divide by 28.35 to change grams to ounces, since an ounce is about 28.35 grams

   $670\text{÷}28.35$$=23.6\text{\hspace{0.17em}oz}$

4. Take away last week's typical weight to see how much was gained over week 24

   $670-568$$=102\text{\hspace{0.17em}g}$

5. Take this week's weight from next week's to see the typical gain in the week ahead

   $785-670$$=115\text{\hspace{0.17em}g}$

6. Compare with the everyday item closest in weight, a 1-pound box of pasta, by dividing one weight by the other

   $\frac{670\text{\hspace{0.17em}g}}{453.6\text{\hspace{0.17em}g}}$$=1.48$

3. Typical weight at 16 weeks: 146 g

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. Divide by 28.35 to change grams to ounces, since an ounce is about 28.35 grams

   $146\text{÷}28.35$$=5.1\text{\hspace{0.17em}oz}$

4. Take away last week's typical weight to see how much was gained over week 16

   $146-117$$=29\text{\hspace{0.17em}g}$

5. Take this week's weight from next week's to see the typical gain in the week ahead

   $181-146$$=35\text{\hspace{0.17em}g}$

6. Compare with the everyday item closest in weight, a medium apple, by dividing one weight by the other

   $\frac{146\text{\hspace{0.17em}g}}{182\text{\hspace{0.17em}g}}$$=0.8$

4. Typical weight at 17 weeks: 181 g

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. Divide by 28.35 to change grams to ounces, since an ounce is about 28.35 grams

   $181\text{÷}28.35$$=6.4\text{\hspace{0.17em}oz}$

7. Take away last week's typical weight to see how much was gained over week 17

   $181-146$$=35\text{\hspace{0.17em}g}$

8. Take this week's weight from next week's to see the typical gain in the week ahead

   $223-181$$=42\text{\hspace{0.17em}g}$

9. Compare with the everyday item closest in weight, a medium apple, by dividing one weight by the other

   $\frac{181\text{\hspace{0.17em}g}}{182\text{\hspace{0.17em}g}}$$=0.99$

10. Take the days so far from the 280 days of a full-length pregnancy to find the time left

    $280-120$$=160\text{\hspace{0.17em}days}$

5. Typical weight at 32 weeks: 1,953 g

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. Divide by 28.35 to change grams to ounces, since an ounce is about 28.35 grams

   $\mathrm{1,953}\text{÷}28.35$$=68.9\text{\hspace{0.17em}oz}$

4. Take away last week's typical weight to see how much was gained over week 32

   $\mathrm{1,953}-\mathrm{1,751}$$=202\text{\hspace{0.17em}g}$

5. Take this week's weight from next week's to see the typical gain in the week ahead

   $\mathrm{2,162}-\mathrm{1,953}$$=209\text{\hspace{0.17em}g}$

6. Compare with the everyday item closest in weight, a 5-pound bag of flour, by dividing one weight by the other

   $\frac{\mathrm{1,953}\text{\hspace{0.17em}g}}{\mathrm{2,267.96}\text{\hspace{0.17em}g}}$$=0.86$

6. Typical weight at 20 weeks: 331 g

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. Divide by 28.35 to change grams to ounces, since an ounce is about 28.35 grams

   $331\text{÷}28.35$$=11.7\text{\hspace{0.17em}oz}$

4. Take away last week's typical weight to see how much was gained over week 20

   $331-273$$=58\text{\hspace{0.17em}g}$

5. Take this week's weight from next week's to see the typical gain in the week ahead

   $399-331$$=68\text{\hspace{0.17em}g}$

6. Compare with the everyday item closest in weight, a 12-ounce bag of coffee beans, by dividing one weight by the other

   $\frac{331\text{\hspace{0.17em}g}}{340.2\text{\hspace{0.17em}g}}$$=0.97$

7. Typical weight at 13 weeks: 73 g

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. Divide by 28.35 to change grams to ounces, since an ounce is about 28.35 grams

   $73\text{÷}28.35$$=2.6\text{\hspace{0.17em}oz}$

6. Take away last week's typical weight to see how much was gained over week 13

   $73-58$$=15\text{\hspace{0.17em}g}$

7. Take this week's weight from next week's to see the typical gain in the week ahead

   $93-73$$=20\text{\hspace{0.17em}g}$

8. Compare with the everyday item closest in weight, a lime, by dividing one weight by the other

   $\frac{73\text{\hspace{0.17em}g}}{67\text{\hspace{0.17em}g}}$$=1.09$

9. Take the days so far from the 280 days of a full-length pregnancy to find the time left

   $280-91$$=189\text{\hspace{0.17em}days}$

8. Typical weight at 12 weeks: 58 g

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. Divide by 28.35 to change grams to ounces, since an ounce is about 28.35 grams

   $58\text{÷}28.35$$=2\text{\hspace{0.17em}oz}$

4. Take away last week's typical weight to see how much was gained over week 12

   $58-45$$=13\text{\hspace{0.17em}g}$

5. Take this week's weight from next week's to see the typical gain in the week ahead

   $73-58$$=15\text{\hspace{0.17em}g}$

6. Compare with the everyday item closest in weight, a lime, by dividing one weight by the other

   $\frac{58\text{\hspace{0.17em}g}}{67\text{\hspace{0.17em}g}}$$=0.87$

9. Typical weight at 39 weeks: 3,435 g

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. Divide by 28.35 to change grams to ounces, since an ounce is about 28.35 grams

   $\mathrm{3,435}\text{÷}28.35$$=121.2\text{\hspace{0.17em}oz}$

7. Take away last week's typical weight to see how much was gained over week 39

   $\mathrm{3,435}-\mathrm{3,236}$$=199\text{\hspace{0.17em}g}$

8. Take this week's weight from next week's to see the typical gain in the week ahead

   $\mathrm{3,619}-\mathrm{3,435}$$=184\text{\hspace{0.17em}g}$

9. Compare with the everyday item closest in weight, a gallon of water, by dividing one weight by the other

   $\frac{\mathrm{3,435}\text{\hspace{0.17em}g}}{\mathrm{3,778}\text{\hspace{0.17em}g}}$$=0.91$

10. Take the days so far from the 280 days of a full-length pregnancy to find the time left

    $280-275$$=5\text{\hspace{0.17em}days}$

10. Typical weight at 11 weeks: 45 g

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. Divide by 28.35 to change grams to ounces, since an ounce is about 28.35 grams

   $45\text{÷}28.35$$=1.6\text{\hspace{0.17em}oz}$

7. Take away last week's typical weight to see how much was gained over week 11

   $45-35$$=10\text{\hspace{0.17em}g}$

8. Take this week's weight from next week's to see the typical gain in the week ahead

   $58-45$$=13\text{\hspace{0.17em}g}$

9. Compare with the everyday item closest in weight, a large egg, by dividing one weight by the other

   $\frac{45\text{\hspace{0.17em}g}}{50\text{\hspace{0.17em}g}}$$=0.9$

10. Take the days so far from the 280 days of a full-length pregnancy to find the time left

    $280-79$$=201\text{\hspace{0.17em}days}$