There Was No Single Greek Foot

01 · EvidenceTwo proposed feet within Athens

Penrose measured the breadth of the Parthenon's upper step as 101.341 English feet on the east front and 101.363 on the west. After corrections, he gave a mean of 101.336 feet. He interpreted that width as 100 Greek feet, taking the name Hecatompedon as support for the count. Dividing the corrected breadth by 100 yields a proposed foot of 1.01336 English feet.¹

The measured width and the ancient count have different kinds of support. Penrose could measure the stone; treating that width as exactly 100 ancient feet was his historical reconstruction. If the count or the chosen measuring line changes, the inferred foot changes too. The decimal places in the survey do not remove that dependency.

In his appendix, Penrose described workmen's marks on fallen stones from the Erechtheum. He reported a rule about 1.066 English feet long, then proposed 1.0632 feet from multiples in the building's dimensions. He also obtained 1.0631 feet from his analysis of the Propylaea. These are Penrose's proposed architectural standards, not surviving official rulers with certified lengths.¹ The contrast is enough to make the question practical: what happens when the same ancient count uses the longer foot?

02 · CalculationHold the count at 600; change the foot

The stadion is the distance unit behind the comparison. Smith's Dictionary of Greek and Roman Antiquities, under Mensura, describes a Greek stadium of 600 Greek feet and discusses literary comparisons with Roman measures. That is a relation between units. It does not supply one universally applicable modern length.²

For a reproducible metric comparison, use 0.3048 metres per English foot as a modern conversion convention. NIST defines the international foot at that value exactly; applying it here is an approximate translation of Penrose's nineteenth-century English measurements, not an assertion that his rods were calibrated to the later definition.³ Keep extra digits during the arithmetic, then round the displayed historical comparison.

The Parthenon reconstruction gives 101.336 ÷ 100 = 1.01336 English feet per proposed Greek foot. Convert it with 1.01336 × 0.3048 = 0.308872128 m; multiply by 600 to obtain about 185.3 m. For the Erechtheum proposal, 600 × 1.0632 × 0.3048 gives about 194.4 m.

The first two model distances differ by about 9.1 m, or 4.9% of the shorter one. That is the effect of the selected standard, not an error bar on either building. Nor are these three rows a census of Greek feet: they are a small, attributed comparison showing why a bare unit name leaves a consequential choice unresolved.

03 · BoundaryA racecourse length is different evidence

Olympia reverses the operation. Penrose's appendix says that its stadium was reported as 192.27 metres long. Accept that reported length for the example and assume a 600-foot course: 192.27 ÷ 600 = 0.32045 m per foot, approximately 320.5 mm. Here the foot is inferred from the track and the count; it is not an independent ruler used to predict the track.¹

Multiplying that inferred foot by 600 returns the starting length automatically. The agreement cannot independently confirm the 600-foot assumption. To test it, one needs evidence outside the arithmetic: the endpoints actually surveyed, the phase of the course, an independently supported standard or a text establishing the relevant count. A precise reported length helps locate the question; it does not answer all of it.

An itinerary introduces another distinction. A distance in stadia between places is a statement about a journey or geographical separation, whereas the length of a stadium is a measurement of a particular structure. Smith's literary unit relations and Penrose's architectural reconstructions should not be treated as interchangeable observations. A route total needs its own textual context and standard before it can be compared with an excavated course.

04 · UseChoose the source before the conversion

Start by identifying what the number describes: a building dimension, a racecourse, a literary distance or a declared comparison. Then name the standard and the source that supports its use. Region and period narrow the choice, but the Athenian example shows why they may not be enough. The measuring line and the reconstructed ancient count can be just as important.

A converter can calculate faithfully from a selected factor. It cannot establish that the factor governed the object being studied. When the historical choice remains unresolved, compare supported alternatives and state the resulting range as a conditional calculation, rather than turning one default into a historical fact. Avoid printing more precision than the evidence warrants.

The Greek foot becomes useful when its context travels with it. Use the length converter for a declared standard, then read False Precision to see what the output's digits can and cannot establish. The Olympia stadium study takes the next question back to a particular place and its surviving course.

05 · SourcesSources

1. Francis Cranmer Penrose, An Investigation of the Principles of Athenian Architecture, second edition (London: Macmillan, 1888), PDF p. 25 (printed p. 11), Parthenon breadth and 100-foot reconstruction; PDF p. 137 (printed p. 123), Erechtheum and Propylaea proposals and the reported Olympia stadium length. Rendered Parthenon page; rendered appendix page.
2. William Smith, ed., A Dictionary of Greek and Roman Antiquities (London: Taylor, Walton and Maberly, 1849), Mensura, PDF p. 777 (printed p. 757), the 600-foot stadium and literary unit comparisons. This historical reference is used for its account of the unit relation, not as a modern consensus foot value.
3. National Institute of Standards and Technology, U.S. Survey Foot, international-foot definition, accessed 13 October 2026. Used only for the modern 0.3048 m conversion convention.