Nobody doubts that the C64 was the greatest selling single computer model of all time, it even made it into the Guinness Book of World Records, but nobody quite knows how many it really was: Most sources say 17 million, others say 22 or even 30 million. With a high degree of confidence, I can now say that Commodore only sold 12.5 million units – how I would know that, you ask, and how do I dare to contradict well-known facts? By analyzing serial numbers!

But let us first examine the existing claims of 17, 22 and 30 million.

Jack Tramiel’s numbers

The numbers 22 and 30 million actually come from Commodore founder Jack Tramiel himself. At the “Impact of the Commodore 64: A 25th Anniversary Celebration” in December 2007 at the Computer History Museum, Tramiel claimed that Commodore sold nearly half a million C64s a month until he left the company in 1984, and he extrapolated this to “between 22 and 30 million units” during the lifetime of the C64. Tramiel’s assistant Michael Tomczyk, who left the company around the same time, uses the same 22 million figure in his 1984 book “Home Computer Wars – An Insider’s Account of Commodore and Jack Tramiel”.

Commodore’s Numbers

But these numbers contradict Commodore’s official sales numbers as researched by Marc Walters: The 1993 Annual Report supposedly states that 17 million units had been sold (production was stopped in April 1994, so this should be very close to the final number). Commodore employee Dr. Peter Kittel confirms the 17 million.

Walters quotes Commodore’s 1993 financial details for the sales numbers between 1990 and 1993:

The following figures are from Commodore annual reports: Fiscal 1990: 700K - 800K (decline begins), fiscal 1991: 800K (non official 1M) fiscal 1992: 650K fiscal 1993: 150K - 200K 1993 Annual Report: 17M total C64, 4.5M C128

Marc Walters’ estimates

Walters also gives his own estimates for 1982 through 1989:

1982: 150K - 300K 1983: 2M 1984: 2M-3M 1985: 2M -3M 1986: 2M -3M 1987: 1M - 2M 1988: 1M - 1.5M 1989: 1M - 1.5M

This data was later picked up by Jeremy Reimer for his Ars Technica article “Total share: 30 years of personal computer market share figures“.

With these numbers, Commodore would have sold between 13.5 and 19 million units. The following graph shows this, with the 17 million figure added as a scaled version of the ranges given:

Putting all reliable data together

This data is quite consistent, but generic sources contradict these steep numbers in the first years:

This data, with Commodore’s own 1990-1993 data added and some of the missing numbers extrapolated, shows a rather flat and consistent sales curve with a single spike in 1984, totalling about 12.5 million units:

In 1984, about 2 to 2.5 million units were sold, which is about 200,000 units per month. There is no way Tramiel’s statement holds true, given the many sources of the early numbers and their consistency. This also falsifies claims of Tramiel’s 22 million and 30 million sold units, which could be approximated by extrapolating the 2.5 million units across a decade – but the existing data shows that the C64 clearly didn’t perform equally well afterwards.

Examining serial numbers

There are two projects that collect C64 serial numbers:

The C64 Serial Registry by the C64 Preservation Project

The C64 Inventory

While the former collects lots of details including case badges and board types, the latter contains information like the video standard as well as photos of all serial number stickers. For the following statistics, we only need the C64 Serial Registry.

Commodore 64 computers were produced in at least 11 different factories worldwide with different and not immediately obvious conventions for serial numbers. But all PCBs, of which there were 16 versions, were manufactured in Hong Kong, and most versions were numbered sequentially, starting at 0 for each new version. The serial number could be found on a sticker on the shield of the cartridge port.

The fact that serial numbers are indeed per board version and are reset to zero for every new board can be seen in the following graph, which was created by sorting the serial numbers by board first and then by number:

If the assumption is correct, serial numbers have to increase linearly until they approach the highest serial number of the board version. All boards should have about the same slope. This is true for all board versions except “250425/A” and “250425/B”, as well as the last two, “250469/A” and “250469/A”.

This can be explained by the bias towards machines from North America in the C64 Serial Registry: About one third of the entries in the database are from the US and Canadian market, but a much smaller percentage of units has actually been sold there – the C64 was very strong in Europe. The first, second and fourth of these board types with a much higher slope were all sold exclusively, and the third one predominantly to PAL markets, i.e. outside North America.

(If the slope there is roughly twice as steep, we can estimate NTSC units are overrepresented in the database by a factor of two, meaning that about 1/6 of all C64 were sold in North America.)

These are the 16 different versions and revisions, the year they first appeared in, the number of boards of this kind in the C64 Serial Registry (that have the board serial number field filled), and the maximum serial number observed:

year board num_seem max_seen 1982 326298 4 1982 326298/A 21 325,512 1982 326298/B 6 1982 326298/C 6 1982 KU-14194HB 16 1983 250407/A 7 208,282 1983 250407/B 50 1,152,644 1983 250407/C 18 1,218,502 1984 250425/- 48 1,273,699 1984 250425/A 9 500,165 1984 250425/B 4 536,345 1986 250466 18 438,001 1987 250469/3 14 444,384 1988 250469/4 29 1,124,586 1989 250469/A 16 1,994,012 1990 250469/B 17 2,242,493

(Note that four of the early versions do not have any easily discoverable serial numbers on them. Also note that the PET 64 and Educator 64 devices, which were basically “326298/A” C64 boards in an all-in-one computer, are also counted, but they sold in very small numbers. The same is true for the ill-fated “250469/B”-based C64GS game console. The portable SX-64 has a different board and is not counted.)

Now we can use the formula for the German Tank Problem to estimate the total number produced for each type of board for which we have the maximum observed serial number:

k is the sample size and m is the highest serial number observed.

year board num_seem max_seen total 1982 326298 4 1982 326298/A 21 325,512 341,012 1982 326298/B 6 1982 326298/C 6 1982 KU-14194HB 16 1983 250407/A 7 208,282 238,036 1983 250407/B 50 1,152,644 1,175,696 1983 250407/C 18 1,218,502 1,286,196 1984 250425/- 48 1,273,699 1,300,233 1984 250425/A 9 500,165 555,738 1984 250425/B 4 536,345 670,430 1986 250466 18 438,001 462,333 1987 250469/3 14 444,384 476,125 1988 250469/4 29 1,124,586 1,163,364 1989 250469/A 16 1,994,012 2,118,637 1990 250469/B 17 2,242,493 2,374,403

For the board types without serial numbers, we can approximate the number of boards produced by scaling the result of board “326298/A” to the number of observed units of the missing ones. Since all boards without serials are from 1982 just like “326298/A”, it is probably not a very bad estimate.

(On the other hand, board “KU-14194HB” has only ever been put into machines produced in Germany and sold in Europe, so because of the bias of the database towards North America, this board type might be underrepresented.)

year board num_seem max_seen total 1982 326298 4 64,955 1982 326298/A 21 325,512 341,012 1982 326298/B 6 97,432 1982 326298/C 6 97,432 1982 KU-14194HB 16 259,818 1983 250407/A 7 208,282 238,036 1983 250407/B 50 1,152,644 1,175,696 1983 250407/C 18 1,218,502 1,286,196 1984 250425/- 48 1,273,699 1,300,233 1984 250425/A 9 500,165 555,738 1984 250425/B 4 536,345 670,430 1986 250466 18 438,001 462,333 1987 250469/3 14 444,384 476,125 1988 250469/4 29 1,124,586 1,163,364 1989 250469/A 16 1,994,012 2,118,637 1990 250469/B 17 2,242,493 2,374,403 12,681,839

So according to this estimate, about 12.5 million Commodore 64 computers were produced, which matches the number above.

(By the way, about 6 million of these had the new smaller board “250469/X” with the HMOS chipset, and almost all machines since 1989, which is about 4.5 million, were sold in Europe.)