Humans are far from perfect and we are prone to make mistakes. It’s why we have the term ‘human error’.

But, these errors don't just happen at random. We’re more likely to make mistakes in certain situations than in others. For example, when making conversions between the metric system of measurements and the imperial system.

The USA still follows the imperial system even though the metric rules are common in the rest of the world. Over the years, this difference in measurement has resulted in some things being lost in translation – or in this case, lost in conversion.

This has led to some rather high-profile blunders which have caused the loss of hundreds of millions of dollars. We’ve compiled a list of 10 of the most notable mistakes made due to conversion errors.

From accidents in space to an escaped tortoise, there have been many mistakes made around (and outside) the globe. Some were easy to rectify, while others cost serious money and, worst of all, some resulted in the loss of human life.

We take a look at ten high-profile examples.

1. NASA’s Mars Climate Orbiter crash lands on the planet

The Mars Climate Orbiter was a satellite created by NASA to collect data on the red planet. It was launched in December 1998 and was set to arrive on Mars within the next year. On 23 September 1999, the Orbiter arrived on Mars, but not in the way it was planned.

NASA announced that the Orbiter was lost, and there had been no communication since. It wasn’t until a full investigation was conducted that they found out what happened.

As with most big projects, multiple teams were working on the spacecraft. The problem was that one team of engineers had used the metric system when taking measurements, whereas another team had used the imperial system.

Due to the difference in metric units and imperial units, the Orbiter’s software made the wrong calculation as it neared the planet. The software calculated the spacecraft’s thruster force in imperial measurements when it should have been done using the metric measurement system.

This resulted in the Orbiter crash landing on Mars and being destroyed. It is said that this project cost NASA between $125 million and $330 million, which was lost forever at the point of impact.

This was one of the most high-profile mistakes caused by an error between metric measurements and SI units.

2. ‘Gimli Glider’ fuel incident

On 29 July 1983, Air Canada's Flight 143 ran out of fuel on its journey from Montreal to Edmonton. Coincidentally, it was the first airline from Air Canada to use metric measures instead of imperial ones. So, what happened?

Well, the journey required 22,300 kg of fuel. Instead of calculating that, the maintenance crew calculated how many liters of fuel they needed to hit 22,300 lbs (pounds). If you know your unit conversion factors, you will understand how big of an error this is.

1 kg equates to 2.2046 lbs. This means that when the crew filled the plane with fuel, it was only half the amount required to make the journey. Therefore, halfway through the journey, at 41,000 feet in the air, the pilots received low fuel pressure warnings. Shortly after, the engines failed.

This meant that all 69 passengers on the plane were essentially in free-fall. Luckily, the captain had over 10 years of experience in gliding an aircraft, and the co-pilot was familiar with the surrounding area.

They were able to glide the aircraft for approximately 100 kilometers to an unused air force base in Gimli, where the plane landed safely. Fortunately, there were no casualties, with some passengers only experiencing minor injuries.

This just goes to show how important it is to know how to convert between measurements.

3. Clarence, the giant tortoise

Clarence, the giant Galapagos tortoise, was taken from the Los Angeles Zoo to Moorpark, California in 2001. He was to participate in the Exotic Animal Training and Management Program at Moorpark College.

Due to Clarence’s age – he was 75 at the time – and his huge size, they built a bespoke enclosure specifically for him. When Moorpark College asked Los Angeles Zoo how big Clarence was, they were told ‘250’. But what Los Angeles Zoo didn’t tell them was whether this was 250 kg or 250 lbs.

Due to the use of the imperial unit system in America, it was assumed that Clarence was 250 lbs, and thus they built an enclosure with this in mind. To give some perspective, the metric equivalent of 250 lbs is 113.40 kg.

Clarence was actually 250 kg heavy, meaning the enclosure they built for him was meant for an animal less than half his size. As such, the enclosure was too flimsy and weak, and Clarence was able to escape his enclosure on the first night.

Luckily, he was found lounging next to the enclosure, and the college was able to build a new heavy-duty home for him. This just shows that it’s important to clarify which measurement units you are referring to.

4. Long jump record not officially recognized

Carol Lewis, a college track athlete, competed in the long jump event at the NCAA Men’s and Women’s Indoor Track Championship in March 1983.

Representing the University of Houston, she broke the record for the longest jump at the competition. Unfortunately for her, it was not registered as an official jump. This is due to the record-keeping rules.

For a record to be officially recorded, the measurement must be made using a metric measurement unit. But unfortunately for Carol, the event organizers did not use a metric tape to measure her jump, they used an imperial tape.

The measurement cannot be converted retroactively and thus, her record-breaking jump did not qualify as an official record.

5. Tokyo Disneyland roller coaster derailed

Typically, there are two kinds of thought processes when considering theme parks and roller coasters. You’re either a thrill seeker who can’t wait to jump on a ride, or you’re someone who imagines the worst-case scenario where the roller coaster falls apart while you’re on it.

Some may call this an irrational fear, but it’s only irrational if it never happens. On 5 December 2003, this fear became real for people at Tokyo Disneyland. The Space Mountain roller coaster was suddenly derailed off its track. It wasn’t until a month later, when Tokyo Disneyland released a report, that some clarification was made on what transpired.

The incident occurred due to a broken axle. It fractured because it was the wrong size and had experienced too much wear and tear. As the report outlined, the axle was ordered in 2002 using measurements taken in 1995. At the time, the measurements were taken in inches, which is imperial. However, since then, the measurements had been changed to the metric unit system.

Therefore, their roller coaster drawings should have changed the axle measurements from 44.14 mm to 45.00 mm. But they weren’t, and the theme park ordered the wrong size.

Thankfully, nobody was injured when the roller coaster derailed, and since this event, Tokyo Disneyland has not experienced any other issues.

6. Korean Air cargo flight

Another flight-related error was made on a cargo flight on 15 April 1999. Flying with Korean Air, the cargo plane was traveling from Shanghai, China, to Seoul, South Korea, with a total of three crew members.

Shortly after take-off, they were given the green light from Shanghai flight control to ascend to 900 meters and then 1,500 meters. However, as the pilots approached 1,500 meters, they began questioning whether they had interpreted flight control's instructions incorrectly.

Assuming they were told to ascend to 1,500 feet and not 1,500 meters (4,900 feet), the pilots began a sharp descent. Unfortunately, in the process of their descent, they lost control of the plane and it began to nosedive.

The pilots were unable to regain control of the plane, and it crashed roughly six miles away from the airport. All crew members were killed, along with five people on the ground, and a further 37 people were injured.

7. Baby was given five times her prescribed dose

In 2004, it was reported that a baby was given five times the prescribed dose of a medication. The baby was prescribed Zantac Syrup to reduce acid production in the stomach at a dose of 0.75 milliliters twice daily.

The pharmacist issuing the bottle had labeled it as ‘¾ teaspoonful twice a day’. A teaspoon is 4.9 ml, meaning the baby received 3.675 ml twice daily instead of 0.75 ml.

It wasn't until a month later when a doctor noticed the mistake that it was corrected. Luckily, the child remained unharmed despite the huge dose.

8. Aircraft lands on runway suspiciously heavy

In 1994, Kalitta Air, then known as American International Airways, was reported to the Federal Aviation Administration for landing 15 tonnes heavier than disclosed.

An investigation found that the cargo airline had made an error when converting from kilograms to pounds, or had simply forgotten to do the conversion in the first place.

9. The sinking of a Swedish warship

On 10 August 1628, Sweden brought a new large warship called Vasa to sea. Although it got off to a good start, 20 minutes into the journey and less than a mile from shore, it sank, killing all 30 people on the ship.

The ship was recovered in the 1950s and after it was measured upon its retrieval, it was found that the shipbuilders had used two different measurement systems when building it.

One side of the ship was built using the ‘Swedish foot’, which equates to 12 inches, while the other side of the ship was built using the ‘Amsterdam foot’, which equates to 11 inches.

This one-inch difference caused one side of the ship to be heavier than the other, and all it took was a little bit of wind to topple the warship. The warship is now held at the Vasa museum as one of Stockholm’s biggest tourist attractions.

10. Christopher Columbus’ miscalculations

Perhaps the most famous conversion error is the one Christopher Columbus made in his search for Asia. He calculated that one degree of latitude equalled 59.5 nautical miles.

But, instead of using the Arabic mile, which is 7,091 feet long, he assumed the use of a Roman mile which is 4,856 feet long. This creates vastly different measurements and partly explains why he stumbled across the Americas as opposed to his destination of Asia.