The dollar's value can be compared to what could have been bought in the United States in the past. Today's dollar value is much less than that of the past because of inflation.
Dollar Strength Index
The U.S. dollar index (USDX) is the common measure for the strength of the dollar. This is a composite that measures the value of the dollar against the six most widely traded currencies. These currencies all use a flexible exchange rate, which means they are not pegged to the dollar, but instead use exchange rates as their valuation.
The amount of trade they have with the United States determines the exchange rate and weight of each currency. This table captures the risk that U.S. companies have to those currencies.