Why Is 4 Sometimes Written IIII Instead of IV?

You probably learned that the Roman numeral for four is IV. Then one day you look closely at an old clock or watch and notice something that seems completely wrong: the four is written as IIII.

It is not a printing mistake. It is not a clockmaker who forgot the rules. And it is not even particularly unusual. IIII has been used on clock faces for centuries, while IV is the form most of us are taught today.

So why does a clock get to break the rule?

The interesting answer is that the rule was never quite as simple as we are taught. Roman numerals changed over time, additive and subtractive forms existed alongside each other, and the familiar IIII on a clock is probably the surviving result of several historical and design traditions rather than one neat decision.

There are two straightforward ways to understand the two forms.

IIII is additive: one plus one plus one plus one equals four.

IV is subtractive: one is placed before five, so five minus one equals four.

The National Archives gives both IIII and IV as representations of four in its guide to reading Roman numerals. The same historical material also shows additive forms such as XXXX alongside the subtractive XL for forty. :contentReference[oaicite:0]{index=0}

That distinction matters because it changes the question. Instead of asking why clockmakers write the number incorrectly, we should ask why one historical form survived in a place where the other became the normal modern convention.

Modern Roman-numeral charts make the system look like it was designed all at once. Learn seven symbols, memorize a handful of subtraction rules, and everything falls into place.

History was much messier.

A 2026 study published in the Proceedings of the National Academy of Sciences describes Roman numeral notation as beginning around 500 BCE as a cumulative, additive base-10 system with a subbase of five. Subtractive expressions appeared later, around 100 BCE, and became more common during the Roman Empire. :contentReference[oaicite:1]{index=1}

Most importantly, subtractive notation did not completely replace additive notation. The two approaches continued to coexist.

That means IIII is not best understood as a corrupted version of IV. It is a surviving form from a period when Roman numerical notation did not behave like the perfectly standardized system we encounter in modern reference charts.

It is tempting to imagine a clean historical progression: Romans used IIII, somebody invented IV, everyone agreed that IV was better, and IIII disappeared.

That is not what happened.

The historical record contains both additive and subtractive forms. The PNAS research describes subtractive notation becoming increasingly common while additive notation remained in use. :contentReference[oaicite:2]{index=2}

The National Archives likewise gives examples in which four can appear as either IIII or IV, and similar variation occurs with larger numbers. :contentReference[oaicite:3]{index=3}

In other words, Roman numerals were not governed by one universal formatting manual. Different periods, places, inscriptions, documents, and practical uses could preserve different conventions.

Once you see that, the clock face stops looking like an exception. It starts looking like exactly what it is: a modern object carrying an old convention forward.

This is where the answer becomes frustratingly honest: we do not have one proven explanation that settles the question.

Several explanations have been proposed over the years. Some involve historical tradition, some involve the appearance of the dial, and some are colorful stories that are difficult to support with evidence.

The strongest conclusion is simply that IIII was already an established form and became part of clockmaking tradition. Once a particular way of laying out a clock face becomes familiar, there is little reason for every new clockmaker to redesign it.

The Washington Post's examination of the question reaches much the same basic conclusion: there are numerous theories, but no definitive explanation for why IIII became the conventional four on so many clock faces. Tradition and aesthetics are plausible explanations, but neither completely solves the historical mystery. :contentReference[oaicite:4]{index=4}

One of the most entertaining explanations involves Jupiter.

The Latin name of the Roman god Jupiter was written as IVPPITER. From this, a story developed that Romans avoided writing IV because it could be read as the beginning of Jupiter's name, and that using IIII kept the sacred name away from ordinary objects.

It is a fantastic story. It is also exactly the kind of historical explanation that should make you suspicious when it gets repeated without evidence.

The theory appears in modern watchmaking explanations, including material from Bulova. :contentReference[oaicite:5]{index=5} But other investigations have pointed out problems with it. The Washington Post, for example, describes the Jupiter explanation as doubtful rather than established fact. :contentReference[oaicite:6]{index=6}

There is another problem: subtractive notation itself developed gradually. If IV was not universally standard in the first place, there is less reason to imagine that an ancient prohibition against those two letters explains the entire later history of IIII.

The Jupiter story may be part of the folklore surrounding Roman numerals. It should not be presented as the proven reason every clock uses IIII.

The more practical explanation has nothing to do with gods or kings. It is about the face of the clock itself.

Look at the twelve positions as groups. The first four use I: I, II, III, IIII. The next four use V: V, VI, VII, VIII. The final four move into X: IX, X, XI, XII.

Using IIII also creates a visual relationship with VIII on the opposite side of the dial. Four characters face four characters, producing a sense of balance that disappears if the four is reduced to two characters as IV.

Watchmaking sources have long promoted visual balance as one explanation for the convention. Seiko, for example, describes the balanced appearance of IIII and VIII as one of the commonly cited reasons for the practice. :contentReference[oaicite:7]{index=7}

But there is an important distinction: a design explanation for why the convention remained attractive is not necessarily evidence for why it originally began.

It is entirely possible for aesthetics to explain the survival of a convention without explaining its original origin.

By the time mechanical clocks became widespread in Europe, Roman numerals were already an old visual language. Clockmakers were not inventing a new numbering system from scratch. They were choosing how an established system should appear on a circular dial.

That made tradition powerful.

Once customers expected a particular style of clock face, manufacturers had an incentive to keep producing it. A familiar four looked like a clock was supposed to look, even if another form was more familiar from modern arithmetic and conversion tables.

The convention became self-reinforcing: old clocks used IIII, new clocks copied old clocks, and the appearance became part of what people recognized as a traditional Roman-numeral clock.

This is one reason historical conventions can survive long after the original circumstances that produced them have disappeared.

There is another useful clue hiding in plain sight: IIII is not universal.

Some famous clocks use IV instead. The Washington Post notes that London's Big Ben uses IV, while Washington's Old Post Office tower uses IIII. :contentReference[oaicite:8]{index=8}

That alone makes a single universal explanation difficult to defend. If IIII were required because IV was historically forbidden, visually impossible, or mechanically inferior, we would expect far less variation.

Instead, clock faces show that both conventions can work perfectly well.

The choice is partly historical and partly stylistic. Some makers preserve the traditional clockmaker's four; others use the modern subtractive form.

There are two different questions hiding inside that sentence.

If you are converting the number 4 into the modern conventional form of Roman numerals, IV is the expected answer.

If you are looking at a historical inscription, an old document, or a traditional clock face, IIII is not automatically an error. It has genuine historical precedent. The National Archives explicitly records IIII and IV as forms of four. :contentReference[oaicite:9]{index=9}

So the best answer is not that one is right and the other is wrong. It is that they belong to different conventions that overlapped across history.

That distinction is easy to lose when we learn Roman numerals as a fixed set of rules rather than as a notation system that evolved over centuries.

The funny thing about the four on a clock is that it exposes something much bigger about Roman numerals.

We tend to think of old numbering systems as finished artifacts. But Roman numerals were used for centuries, changed over time, developed competing conventions, and eventually became something very different: a visual language used long after people stopped relying on them for everyday calculation.

That is why IIII can survive on a modern watch even though most people would write IV everywhere else.

The clock is not necessarily breaking the rules. It is carrying a piece of the history of those rules on its face.

And that may be the real reason the strange four has survived: not because anyone forgot how Roman numerals work, but because sometimes a convention becomes more recognizable than the rule that created it.