Pounds to short tons (lb to ton)

One pound is exactly 0.0005 short tons. That ratio belongs to the customary system itself and is much older than any link to metric: the 1959 international yard and pound agreement later fixed the yard and the pound against the meter and the kilogram, but it left the ratios between customary units (feet to the yard, ounces to the pound, cups to the gallon) exactly as they were.

Worked through: 2,205 lb x 0.0005 = 1.1025 ton.

Going the other way, one short ton is 2,000 pounds.

For mental arithmetic: Divide by 2,000: halve it and move the decimal three places.

Two thousand pounds to the short ton, which is the one Americans mean by 'ton' without qualification. There are three tons and they are all close enough to be confused and far enough apart to matter: the short ton at 2,000 lb, the long or imperial ton at 2,240 lb, and the metric tonne at 1,000 kg or about 2,205 lb. The long ton's 2,240 comes from twenty hundredweight of 112 pounds each. Freight, scrap and aggregate pricing all turn on which one a contract names.

Precision is worth matching to the input. A measurement given as 500 lb carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.