Test Lab · Prototype
One base, many possible units
A surveyed length does not determine an ancient unit until a count is assumed. Change the count and follow the consequence.
Keep the surveyed base fixed
Petrie's four reconstructed casing sides have a mean of 9,068.8 English inches. The surviving features and their reconstruction underpin this figure; it is not a direct measurement of an intact base.
| Side | Length | Difference from mean |
|---|---|---|
| North | 9,069.4 | +0.6 |
| East | 9,067.7 | −1.1 |
| South | 9,069.5 | +0.7 |
| West | 9,068.6 | −0.2 |
Source: Petrie 1883, pp. 39–40. Residuals are differences from the mean, not uncertainty intervals or a universal construction tolerance.
Change the divisor
Try a whole-number count from 400 to 480. This interval is chosen for exploration; it is not a historically established range.
9,068.8 ÷ 440 ≈
English inches per assumed unit
440 × (9,068.8 ÷ 440) = 9,068.8 inches
A perfect return is built into the calculation
For every count in this experiment, multiplying the derived unit by that same count returns the original base before display rounding. That fit cannot independently establish the ancient count.
Petrie's own table describes the base deduction conditionally, using a count of 440 cubits. The experiment starts there, but changing the count does not identify another historical cubit.
The six decimal places show the arithmetic. They add no precision to the survey, and the tool does not calculate an uncertainty interval.
Follow the evidence
W. M. Flinders Petrie, The Pyramids and Temples of Gizeh (1883), pp. 39–40 and 178. Historical English inches are retained without claiming modern calibration. Digitised source.
Continue with Petrie’s Giza survey: dimensions, errors and cubit estimates for the survey and uncertainty, or the Seked calculator for an explicitly declared pyramid model.