187 JPMorgan Chase & Co./2018 Form 10-K While the notional amounts disclosed above give an indication of the volume of the Firm’s derivatives activity, the notional amounts significantly exceed, in the Firm’s view, the possible losses that could arise from such transactions. For most derivative contracts, the notional amount is not exchanged; it is used simply as a reference to calculate payments. The following table summarizes the notional amount of derivative contracts outstanding as of December 31, 2018 and 2017. Notional amount of derivative contracts (a) For more information on volumes and types of credit derivative contracts, refer to the Credit derivatives discussion on pages 195-197. (b) Represents the sum of gross long and gross short third-party notional derivative contracts. (c) The prior period amounts have been revised to conform with the current period presentation. Notional amounts (b) December 31, (in billions) 2018 2017 Interest rate contracts Swaps $ 21,763 $ 21,043 Futures and forwards 3,562 4,904 Written options 3,997 3,576 Purchased options 4,322 3,987 Total interest rate contracts 33,644 33,510 Credit derivatives (a) 1,501 1,522 Foreign exchange contracts Cross-currency swaps 3,548 3,953 Spot, futures and forwards 5,871 5,923 Written options 835 786 Purchased options 830 776 Total foreign exchange contracts 11,084 11,438 Equity contracts Swaps 346 367 Futures and forwards 101 90 Written options 528 531 Purchased options 490 453 Total equity contracts 1,465 1,441 Commodity contracts Swaps 134 133 $^{(c)}$  Spot, futures and forwards 156 168 Written options 135 98 Purchased options 120 93 Total commodity contracts 545 492 $^{(c)}$  Total derivative notional amounts $ 48,239 $ 48,403 $^{(c)}$ 