Why Do We Use ‘Miles’ in Some Countries and ‘Kilometers’ in Others?

We use different units because countries used to measure things in different ways. In some places, people counted distance by how many paces a horse could take, that's where miles came from. In other places, they used parts of the body or nature, like how long a meter is, that’s where kilometers came from. Over time, countries stuck with their own way of measuring things.