Illustration of pirates ambushing a ship

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How Pirates Hijacked the Metric System

The U.S. has never adopted the metric system. A kidnapped scientist and lost mathematical treasure could help explain why.

March 2025
By Andrew Klein | Illustrated by Rafa Alvarez

More than 230 years ago, a band of buccaneers raided a ship headed for America—possibly changing the course of U.S. history. The pirates stole scientific models meant to help convince the U.S. government to adopt the metric system—a measuring system with units based on multiples of 10. Today the U.S. is one of the few countries whose road signs list distance in miles rather than kilometers, scales read weights in pounds instead of kilograms, and cartons of milk come in gallons instead of liters. Pirates may be partly to blame.

METRIC CONVERSIONS

Today, most of the world uses the metric system to measure length, mass, and volume. The U.S. still uses the customary system in most situations—but not all, such as when doing scientific research. This has resulted in an interesting mix of measurements. Here is how to convert between the two systems.

Use the information in the chart above to convert common measurements between metric and customary units. Round answers to the nearest hundredth. Record your work and answers on our answer sheet.

American cars display a vehicle’s speed in miles per hour. If a car is traveling at a speed of 35 miles per hour, how fast is that in kilometers per hour?

The speed limit on many Canadian freeways is 100 kilometers per hour. Would a car traveling 65 miles per hour be obeying this speed limit? Why or why not?

Even in the U.S., scientists conduct research using metric measurements. A chemist’s flask holds volumes up to 250 milliliters. How much will it hold in fluid ounces?

An empty 250-milliliter flask weighs 136 grams. How much in total would 50 flasks weigh in pounds?

Each race in a track-and-field competition uses metric measurements. If a long-distance runner completes a 5-kilometer race, how far did they run in miles?

A sprinter practices for the 100-meter dash on a football field that’s measured in yards. The field of play is 100 yards and each end zone is 10 yards. Which sections of the field would come closest to 100 meters? Explain on a separate sheet of paper. (Hint: 1 yard = 3 feet)


MATH TALK: Do you think the U.S. should have chosen the metric system over the customary system?

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Metric Measurements, Customary Measurements
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