MadSci Network: Science History

Re: Why do clock faces use Roman IIII not IV for the number four?

Date: Mon Apr 2 16:07:18 2001
Posted By: Dan Berger, Faculty Chemistry/Science, Bluffton College
Area of science: Science History
ID: 980695274.Sh

Why do clock faces use Roman IIII not IV for the number four?

I collect Telechron electric clocks and have noticed this peculiar use of Roman numerals. Even old European wind-up clocks from 1800's use the same numerals. Some manufacturers of cheap battery clocks do not know about this and mistakenly use IV.

Roman numberals are thoroughly discussed, with references, at this excellent website. But to answer your specific question:
This answer is based on Paul Lewis' site on Roman numerals.
Roman numerals can get quite long, and so one may use contractions via the "subtraction principle" in which a smaller number appears before a larger to indicate subtraction: thus, IV = "one from five" for 4 or CM = "one hundred from one thousand" for 900. Such contractions have never been used in any consistent way.

Some historical examples:

  • The Roman Colosseum was completed in AD 80. Doors 23 through 54 survive, and are numbered. The contractions IV and IX are not used, but XL is used for 40 so that doors 44 and 49 are numbered XLIIII and XLVIIII.

  • A piece of woodcarving in the church of Sant'Agnese fuori le mura is dated MCCCCCCVI (you'd expect MDCVI); see the image above.

  • A carved stone plaque on the Castel Sant'Angelo, built by Pope Alexander VI (pontiff from 1492-1503), is dated MCCCCLXXXXV--no contractions at all!

  • Here's a system opposite to that on the Colosseum: In the Vatican Museum, the Borgia Rooms are numbered using Roman numerals including IV and IX, but after room 39 comes room XXXX, then XXXXI; later XXXXIV, and later still XXXXIX, then L. The date of this numbering is not known but is certainly the 20th Century AD.
Clock faces are said to use IIII to balance the VIII opposite; but not all clocks do this, and it's not just a modern aberration. I have owned good-quality watches which use IV, and one of the most famous clocks in the world does, too. In the image of the clock face on the linked page, you can easily see that IV is used rather than IIII.

Dan Berger
Bluffton College

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