Pregnancy Due Date Ranges

This table attempts to estimate your probability of going into labor on different individual days based on your estimated due date. If you don't know your due date, or just want a handy daily page to tell you where you're at, use the pregnancy calendar.

It's based on the idea that the average pregnancy lasts 40 weeks with a standard deviation of about 10 days. This means you're more likely to go into labor on one of the days close to your due date. For instance, about half of all babies are born within a week of their date. Scroll to the bottom of this page if you want to know more about where I got these numbers.

The following dates are based on an estimated due date of October 21st, 2020.

Change due date:
Month Day Year
Date Progress Overall probability of
spontaneous labor
Current probability of
spontaneous labor
probability of a pregnant woman at this stage going into labor
On this date By this date On this date By this date On this date Within 3 days Within 5 days Within 7 days
Wednesday September 16th, 2020 35W, 0D 0.01% 0.02% -% -% -% 0.1% 0.1% 0.2%
Thursday September 17th, 2020 35W, 1D 0.01% 0.03% -% -% -% 0.1% 0.2% 0.3%
Friday September 18th, 2020 35W, 2D 0.02% 0.05% -% -% -% 0.1% 0.2% 0.4%
Saturday September 19th, 2020 35W, 3D 0.02% 0.07% -% -% -% 0.1% 0.3% 0.6%
Sunday September 20th, 2020 35W, 4D 0.03% 0.1% -% -% -% 0.2% 0.4% 0.7%
Monday September 21st, 2020 35W, 5D 0.04% 0.13% -% -% -% 0.2% 0.5% 0.9%
Tuesday September 22nd, 2020 35W, 6D 0.06% 0.19% -% -% 0.1% 0.3% 0.6% 1.2%
Wednesday September 23rd, 2020 36W, 0D 0.08% 0.26% -% -% 0.1% 0.4% 0.8% 1.5%
Thursday September 24th, 2020 36W, 1D 0.1% 0.35% -% -% 0.1% 0.5% 1% 1.9%
Friday September 25th, 2020 36W, 2D 0.14% 0.47% -% -% 0.1% 0.6% 1.3% 2.4%
Saturday September 26th, 2020 36W, 3D 0.18% 0.62% -% -% 0.2% 0.8% 1.7% 3%
Sunday September 27th, 2020 36W, 4D 0.22% 0.82% -% -% 0.2% 1% 2.1% 3.7%
Monday September 28th, 2020 36W, 5D 0.28% 1.07% -% -% 0.3% 1.2% 2.5% 4.5%
Tuesday September 29th, 2020 36W, 6D 0.35% 1.39% -% -% 0.4% 1.5% 3.1% 5.4%
Wednesday September 30th, 2020 37W, 0D 0.44% 1.79% -% -% 0.4% 1.8% 3.8% 6.4%
Thursday October 1st, 2020 37W, 1D 0.54% 2.28% -% -% 0.6% 2.2% 4.5% 7.6%
Friday October 2nd, 2020 37W, 2D 0.66% 2.87% -% -% 0.7% 2.7% 5.4% 8.9%
Saturday October 3rd, 2020 37W, 3D 0.79% 3.59% -% -% 0.8% 3.2% 6.3% 10.4%
Sunday October 4th, 2020 37W, 4D 0.94% 4.46% -% -% 1% 3.8% 7.4% 11.9%
Monday October 5th, 2020 37W, 5D 1.11% 5.48% -% -% 1.2% 4.4% 8.6% 13.7%
Tuesday October 6th, 2020 37W, 6D 1.3% 6.68% -% -% 1.4% 5.2% 9.8% 15.5%
Wednesday October 7th, 2020 38W, 0D 1.5% 8.08% -% -% 1.6% 6% 11.2% 17.5%
Thursday October 8th, 2020 38W, 1D 1.71% 9.68% -% -% 1.9% 6.9% 12.7% 19.7%
Friday October 9th, 2020 38W, 2D 1.94% 11.51% -% -% 2.2% 7.8% 14.3% 21.9%
Saturday October 10th, 2020 38W, 3D 2.18% 13.57% -% -% 2.5% 8.8% 16% 24.2%
Sunday October 11th, 2020 38W, 4D 2.42% 15.87% -% -% 2.9% 9.9% 17.8% 26.6%
Monday October 12th, 2020 38W, 5D 2.66% 18.41% -% -% 3.3% 11.1% 19.7% 29%
Tuesday October 13th, 2020 38W, 6D 2.9% 21.19% -% -% 3.7% 12.3% 21.6% 31.5%
Wednesday October 14th, 2020 39W, 0D 3.12% 24.2% -% -% 4.1% 13.5% 23.6% 34%
Thursday October 15th, 2020 39W, 1D 3.33% 27.43% -% -% 4.6% 14.9% 25.6% 36.6%
Friday October 16th, 2020 39W, 2D 3.52% 30.85% -% -% 5.1% 16.2% 27.7% 39.2%
Saturday October 17th, 2020 39W, 3D 3.68% 34.46% -% -% 5.6% 17.6% 29.8% 41.7%
Sunday October 18th, 2020 39W, 4D 3.81% 38.21% -% -% 6.2% 19.1% 31.9% 44.2%
Monday October 19th, 2020 39W, 5D 3.91% 42.07% -% -% 6.7% 20.6% 34% 46.7%
Tuesday October 20th, 2020 39W, 6D 3.97% 46.02% -% -% 7.4% 22.1% 36.2% 49.2%
Wednesday October 21st, 2020 40W, 0D 3.99% 50% 8% 0% 8% 23.6% 38.3% 51.6%
Thursday October 22nd, 2020 40W, 1D 3.97% 53.98% 7.9% 8% 8.6% 25.1% 40.4% 54%
Friday October 23rd, 2020 40W, 2D 3.91% 57.93% 7.8% 15.9% 9.3% 26.7% 42.5% 56.2%
Saturday October 24th, 2020 40W, 3D 3.81% 61.79% 7.6% 23.6% 10% 28.2% 44.5% 58.5%
Sunday October 25th, 2020 40W, 4D 3.68% 65.54% 7.4% 31.1% 10.7% 29.8% 46.6% 60.6%
Monday October 26th, 2020 40W, 5D 3.52% 69.15% 7% 38.3% 11.4% 31.3% 48.6% 62.7%
Tuesday October 27th, 2020 40W, 6D 3.33% 72.57% 6.7% 45.1% 12.1% 32.9% 50.5% 64.7%
Wednesday October 28th, 2020 41W, 0D 3.12% 75.8% 6.2% 51.6% 12.9% 34.4% 52.4% 66.6%
Thursday October 29th, 2020 41W, 1D 2.9% 78.81% 5.8% 57.6% 13.7% 36% 54.3% 68.5%
Friday October 30th, 2020 41W, 2D 2.66% 81.59% 5.3% 63.2% 14.4% 37.5% 56.1% 70.2%
Saturday October 31st, 2020 41W, 3D 2.42% 84.13% 4.8% 68.3% 15.2% 39% 57.9% 71.9%
Sunday November 1st, 2020 41W, 4D 2.18% 86.43% 4.4% 72.9% 16.1% 40.5% 59.6% 73.5%
Monday November 2nd, 2020 41W, 5D 1.94% 88.49% 3.9% 77% 16.9% 42% 61.3% 75.1%
Tuesday November 3rd, 2020 41W, 6D 1.71% 90.32% 3.4% 80.6% 17.7% 43.4% 62.9% 76.4%
Wednesday November 4th, 2020 42W, 0D 1.5% 91.92% 3% 83.8% 18.6% 44.8% 64.5% 77.8%
Thursday November 5th, 2020 42W, 1D 1.3% 93.32% 2.6% 86.6% 19.5% 46.3% 65.9% 79.2%
Friday November 6th, 2020 42W, 2D 1.11% 94.52% 2.2% 89% 20.3% 47.6% 67.3% 80.5%
Saturday November 7th, 2020 42W, 3D 0.94% 95.54% 1.9% 91.1% 21.1% 48.9% 68.8% 81.6%
Sunday November 8th, 2020 42W, 4D 0.79% 96.41% 1.6% 92.8% 22% 50.1% 70.2% 82.7%
Monday November 9th, 2020 42W, 5D 0.66% 97.13% 1.3% 94.3% 23% 51.6% 71.4% 83.6%
Tuesday November 10th, 2020 42W, 6D 0.54% 97.72% 1.1% 95.4% 23.7% 53.1% 72.8% 84.6%
Wednesday November 11th, 2020 43W, 0D 0.44% 98.21% 0.9% 96.4% 24.6% 54.2% 73.7% 85.5%
Thursday November 12th, 2020 43W, 1D 0.35% 98.61% 0.7% 97.2% 25.2% 55.4% 74.8% 86.3%
Friday November 13th, 2020 43W, 2D 0.28% 98.93% 0.6% 97.9% 26.2% 56.1% 75.7% 87.9%
Saturday November 14th, 2020 43W, 3D 0.22% 99.18% 0.4% 98.4% 26.8% 57.3% 76.8% -%
Sunday November 15th, 2020 43W, 4D 0.18% 99.38% 0.4% 98.8% 29% 58.1% 79% -%
Monday November 16th, 2020 43W, 5D 0.14% 99.53% 0.3% 99.1% 29.8% 59.6% -% -%
Tuesday November 17th, 2020 43W, 6D 0.1% 99.65% 0.2% 99.3% 28.6% 62.9% -% -%
Wednesday November 18th, 2020 44W, 0D 0.08% 99.74% 0.2% 99.5% 30.8% -% -% -%
Thursday November 19th, 2020 44W, 1D 0.06% 99.81% 0.1% 99.6% 31.6% -% -% -%
Friday November 20th, 2020 44W, 2D 0.04% 99.87% 0.1% 99.7% 30.8% -% -% -%

Probability of labor on a given day

Probability of labor by a given day

Notes and disclaimers

All percentages are estimates based on mathematical averages and should not be taken terribly seriously... just because you only have 5% chance of going into labor two weeks early, that doesn't mean you should schedule a trip to the bahamas that weekend (see xkcd to get what I mean here).

You should (obviously) listen to your doctor or midwife on all matters related to pregnancy and childbirth. Just because this chart tells you that a 42W pregnant woman has a high chance of delivering in the next seven days, it doesn't mean it's healthy for her to be pregnant for seven more days. If your doctor wants to increase probability of delivery by inducing labor, there's probably a good reason.

Finding good distribution statistics on spontaneous labor is interesting. I have not found a study with an exact daily breakdown of when babies are born. However I have read way too much on this topic, so I can tell you that my favorite published research is The length of human pregnancy as calculated by ultrasonographic measurement of the fetal biparietal diameter (H. Kieler, O. Axelsson, S. Nilsson, U. Waldenströ) which a very nice table of 10 published studies, which found various means between 272-283 days. The study contributes their own results as well, analyzing nearly 2000 mothers who went into labor spontaneously, and there's graphs of what they found. They found a mean around 280 days, and standard deviations between 8-11 days. There's a big list of other studies and answers in the Introduction to my due date survey results.

Which leads to this topic... I am also in the process of collecting my own statistics. If you have had a baby, please take my due date survey. Oddly enough, the numbers I've collected so far support my messy hunch that pregnancy length has a 40-week mean and 9-10 day standard deviation. So go me.

Anyway if you have better research, drop me an e-mail (spacefem@spacefem.com).

Charts are generated by flot.

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