What DAY was your Model T built? Try this out...

[ModelTMitch]

You may have seen my previous post, where I detailed my crude formula for calculating the build date of a Model T, based on the serial number and a few other pieces of data.

I have finally finished my new Windows program, which takes all the guesswork out of the calculation.
You no longer need to refer to the Serial Number Database to work out the year and month - the database is built into the program, so it's all done for you!
Simply punch in your Model T's serial number and click Calculate, and the entire build date is magically shown to you!

Please let me know if it works for you - I would really appreciate the feedback
Of course, it's not guaranteed, and it does have to make some assumptions, but all things being equal, I believe it's reasonably accurate.

Both the legacy Excel calculator and the new Windows program can be downloaded from here:

https://www.fordmodelt.net/model-t-ford-build-date.htm

Ford Model T Build Date Calculator

Curious to know exactly what day your Model T was built?

I have worked out a crude formula for calculating the build date of your Model T, in an ideal world, where everything is perfect!

Of course, it's not guaranteed, and we have to make some assumptions, but all things being equal, it's reasonably close.
It assumes that the engine was fitted into the car on the same day it received its serial number, as Ford called them "Motor Numbers". Naturally, this is unlikely to be the case, so in truth, you're calculating the date the engine was made, not so much the car.

If anyone has any idea when engines received their serial numbers, I'd love to hear from you. Were they stamped as each block was cast? Or were they stamped as the engine was installed in a car? If it's the latter, then the following formula would be more accurate!

Here's how my formula works, and I've used my own Model T as an example.

1. Start with the Serial Number of your Model T, in my case, it's 10114515.
2. Using the Model T Serial Number database, we can see that number lands in June of 1924, between serial numbers 9984772 and 10126471.
3. Take note of the number of days in the build month, that's 30 in this example (June).
4. Now we need to know how many Model T's were made in the build month, to find this, subtract the first serial of the month from the last serial of the month, in this example we get 141699.
5. We need to know the average daily production figure, to calculate this, divide the total for the month, in this case 141699, by the number of days in the month, in this case that's 30, which yields an answer of 4723.
6. Now we need to know the number of Model T's built between ours, and the end of the month. Subtract your serial number from the last serial of the month, so for me that's 10126471 - 10114515 = 11956.
7. Now we can calculate the number of days between your Model T, and the final car of the month. Divide the number of cars in step 6, by the average daily production figure, in this example that's 11956 ÷ 4723 = 3.
8. Finally, subtract the answer from the number of days in the month to reveal the approximate build date: 30 - 3 = 27. Meaning my Model T was built (roughly) around the 27th June 1924.

[jab35]

Your model appears to include Saturdays and Sundays as 'full' production days, which is incorrect. The book 'Ford Methods and Ford Shops' indicates Highland Park assembly workers worked two 8hr shifts M-F and 4 hrs on weekends, 44 hr per week each shift. And of course, there were a few holidays each year as well when no cars were assembled. And then there's the cars that were assembled at the Ford branches,,,,,,jb

[varmint]

The math looks like a lot of fun. I don't know if there is any information about shift efficiency that you can use to weight the shifts unevenly.

Our 10-26-1926 coupe was assembled in Arabi, LA which is a long distance from Dearborn, Michigan.

[ModelTMitch]

Your model appears to include Saturdays and Sundays as 'full' production days, which is incorrect. The book 'Ford Methods and Ford Shops' indicates Highland Park assembly workers worked two 8hr shifts M-F and 4 hrs on weekends, 44 hr per week each shift. And of course, there were a few holidays each year as well when no cars were assembled. And then there's the cars that were assembled at the Ford branches,,,,,,jb

Yes, it does include Saturdays and Sundays in full, as my previous post states, the program formula is crude
I don't think it's possible to be 100% accurate, because we don't know if the factory was ever closed for one day here and there due to unforeseen circumstances, such as power outage, or if it was, specifically what day(s).
We know that Ford documented pretty much everything, but making a calculator that factors in every single "what if", would be almost impossible.
My calculator keeps it simple and is based on averages, which works to a certain degree. but thank you for the feedback