Currency Rate

Copper Coins:

- Halfpenny (lowest possible denomination)

- Penny, equals 2 Halfpennies

- Half Groat, equals 2 pennies

- Groat, equals 4 pennies

- Star, equals 2 Groats or 8 pennies

Silver Coins:

- Stag, equals 7 stars or 56 pennies

- Moon, equals 49 stars or 392 pennies

Gold Coins:

- Dragons, equals 30 Moons, 210 Stags, or 11,760 pennies

The conversion rate is 1 Groat = 1 US dollar

We assume that Essos and Westeros use the same currency

This might seem insane because when Ned Stark became the right hand he learnt that they would host a tournament which offered 40,000 Gold Dragons to the winner of the joust, 20,000 to the runner up, and 20,000 to the best archer. If we did the math that would equal a total of around a quarter billion US dollars of tournament rewards. That's just what the Game of Thrones Wiki states so I will work around that.