Three different tons
In the United States a ton is the short ton of 2,000 pounds (907.18 kg). In Britain the traditional long ton is 2,240 pounds (1,016.05 kg), a figure that survives in shipping. The metric tonne is 1,000 kg, which is 2,204.62 pounds — between the two, and closer to the long ton. The calculator converts the US short ton and lists the other two, because a ten-ton figure can mean anywhere from 20,000 to 22,400 pounds depending on who wrote it.
Telling them apart
Spelling helps: tonne is always metric. Context helps more: US freight, truck ratings and pickup classes (half-ton, three-quarter-ton) are short tons; ship displacement is long tons or tonnes; anything from a European or Asian source is tonnes. When a document just says “tons” with no country, assume short tons in the US and tonnes everywhere else.