The Roman mile (mille passus) was a thousand paces, about 1,479 metres by modern estimates, a little shorter than today's mile. Roman road distances, milestones and itineraries were counted in these miles, while our map measures in kilometres.
Key takeaways
- The Roman mile was a thousand paces, where a pace was two steps, and it was slightly shorter than the modern mile [1].
- Roman roads, milestones and travel books counted distance in these miles, so ancient figures are not in kilometres.
- Every length on our map is in kilometres, for example the Fosse Way at 372 km, so no conversion is needed to read it.
- The exact length of the Roman mile is an estimate, which is one reason ancient distances only roughly match modern measurements.
How the Roman mile worked
The Roman mile was called mille passus, which is Latin for "a thousand paces". A pace here meant two steps, the distance from where one foot lands to where the same foot lands again, so a thousand of them added up to a long stretch of walking [1]. It was fixed more firmly when the general Agrippa set a standard Roman foot in 29 BC, and a pace was then counted as five of those feet. That made the mile 5,000 Roman feet [1].
Nobody has a Roman mile to measure today, so its length is a modern estimate. The usual figure is about 1,479 metres, slightly less than the 1,609 metres of the modern international mile [1].
The mile mattered because the Romans measured roads with it. Surveyors used rods and instruments to lay out distances, and the result was marked along the way by stone milestones that counted miles [1][3]. Travel books such as the Antonine Itinerary listed the miles between one stopping place and the next [1]. The English word "mile" comes from the Latin mille passus [1].
This is why a modern map of a Roman road never matches an ancient number exactly. The ancient figure is a count of miles, usually rounded, between named places. The modern figure is a measured length of a line.
An example from our data
Our map has no Roman miles in it. Every length is in kilometres, measured along the digitised line from the Itiner-e atlas, so you can compare roads without converting anything. The Fosse Way comes to 372 km in our data, made of 34 segments. Watling Street is 352 km, and the shorter Stane Street, which linked London and Chichester, is 93.3 km.
If you read an ancient itinerary that gives the miles between two places on one of these roads, you can expect it to differ a little from our figure. The itinerary counts between towns and rounds, while our line follows a mapped course that is mostly a scholarly reconstruction. Only 2.7% of the whole network is classed as certain, so a difference of a few kilometres says more about the uncertainty of the line than about the Romans' arithmetic. See the facts page for how the lengths are worked out, and how to read the map for what the certainty colours mean.
For scale, the whole network in our data is 299,171 km, and the longest named road is the Via Egnatia at 1,165 km.
The thing people get wrong
People often assume the Roman mile was the same as the modern mile, or that a "league" and a "mile" were interchangeable. They were not. The Roman mile was a little shorter than a modern mile [1], and the English mile has its own history: in 1593 an English law set the statute mile at 1,760 yards, a different thing from the Roman unit [1]. So a Roman writer's "twenty miles" is not twenty modern miles, so ancient figures should not be read as modern miles.
A second mistake is to think the milestone counted from the nearest town. Some milestones gave a distance, but many Roman milestones only record the name of the reigning emperor and no distance at all [3]. They were as much a statement of who was responsible for the road as a measuring aid.
Frequently asked questions
How many kilometres was a Roman mile?
About one and a half kilometres. Modern estimates put it at roughly 1,479 metres, so it was a little shorter than the modern mile.
Why is the word mile Roman?
English mile comes from the Latin mille passus, a thousand paces, by way of Old English.
Does the map show Roman miles?
No. Every length on the map is in kilometres, measured along the digitised line.
Sources
- Roman mile, Wikipedia.
- Roman roads, Wikipedia.
- Milestone, Wikipedia.
- Every figure from our own map is worked out from the datasets on the data sources page (checked against Itiner-e version 2024 1.3).