The IMF determines the value of SDRs (Special Drawing Rights) daily by summing, in US dollars, the values - which are based on market exchange rates - of a weighted basket of currencies. The basket and weights are subject to revision from time to time.

The SDR is calculated daily as the sum of the values in dollars of specific amounts for five countries (France, Germany, Japan, the UK and the US) of the four currencies in the SDR basket (euro, dollar, Japanese yen, pound sterling), using exchange rates quoted at 12.00 noon on the London Market. The basket and its weights are reviewed every five years. The basket is determined as the five IMF countries having the largest exports of goods and services in the five-year period ending 12 months before the review. The weights thus reflect the importance of these currencies in international trade and reserves.

The nominal exchanges rate is the price of one currency in terms of another.