How do I convert miles to US leagues?
Divide by 3. The US league is three statute miles, so 12 miles is 4 leagues and 30 miles is 10.
In metric that's 4,828.032 m per league, exactly.
There have been plenty of other leagues over the centuries, mostly somewhere around an hour's walk, and they don't agree with each other – so check which one an old source meant before you trust the sum.
What is a mile?
A mile is an imperial and US unit of length, exactly 1,609.344 meters. The word comes from the Latin mille passus, 'a thousand paces', where a pace was two steps of a marching legionary.
A mile is equivalent to 1760yds or 5280ft.
Road distances in the US and UK are signed in miles, while nearly every other country uses kilometers. Aviation and shipping use the nautical mile instead, which is a different length (1,852 meters).
What is a US league?
A US league is three miles or 15,840 feet. The word comes from the Late Latin leuca, a Gaulish measure traditionally taken as an hour's walk.
The league was used for the distance between towns and for a ship's run at sea. The mile and the kilometer replaced it, and it now mostly turns up in older books. A US league of three miles is about 4.83km.