# R5 | anthropic/claude-opus-5 | run 1

## Prompt

How many kilometers are in 100 miles? Show the conversion factor and cite a source for it.

## Response

100 miles = 160.9344 kilometers.

## Conversion Factor

The exact, internationally agreed definition is:

\[ 1 \text{ mile} = 1.609344 \text{ km} \]

This follows from the 1959 International Yard and Pound Agreement, which defined the international yard as exactly 0.9144 meters. Since a mile is 1,760 yards:

\[ 1760 \times 0.9144 = 1609.344 \text{ m} = 1.609344 \text{ km} \]

## Calculation

\[ 100 \times 1.609344 = 160.9344 \text{ km} \]

Rounded practically: **160.93 km**, or roughly **161 km**.

## Source

The definition is documented by the U.S. National Institute of Standards and Technology in NIST Special Publication 811, *Guide for the Use of the International System of Units (SI)*, Appendix B, which lists the mile-to-kilometer factor as exactly 1.609344 — [NIST SP 811](https://www.nist.gov/pml/special-publication-811). The underlying yard definition appears in NIST's refinement of values documentation — [NIST Handbook 44](https://www.nist.gov/pml/owm/publications).

Note that the *nautical* mile is different: exactly 1.852 km by international definition, so 100 nautical miles = 185.2 km.

Would you like the reverse conversion or a quick reference table for other common distances?
