Table: Estimation of Wizarding Currency into Muggle Money
1 Galleon 1 Sickle 1 Knut
Pound Sterling GBP £4.93 £0.29 £0.01
U.S. Dollar USD $7.35 $0.46 $0.02
Euro EUR €5.90 €0.34 €0.01
Japanese Yen JPY ¥653.66 ¥37.91 ¥1.31
Swiss Franc CHF 7.75 Fr. 0.45 Fr. 0.02 Fr.
Australian Dollar AUD $7.96 $0.46 $0.02
Canadian Dollar CAD $7.82 $0.45 $0.02
Danish Kroner DKK 43.94 kr. 2.55 kr. 0.09 kr.
South African Rand ZAR R 54.01 R 3.13 R 0.11
Indian Rupee INR Rs. 354.67 Rs. 20.57 Rs. 0.71
Hong Kong Dollar HKD $60.64 $3.52 $0.12
Philippine Peso PHP ₱342.24 ₱19.85 ₱0.68
Thai Baht THB ฿245.36 ฿14.43 ฿0.49
Swedish Krona SEK 53.81 kr 3.12 kr 0.11 kr
Serbian Dinar RSD 631.25 RSD 36.61 RSD 1.26 RSD
Argentine Peso ARS $25.34 $1.49 $0.03

According to J.K. Rowling, the approximate value of a Galleon is "About five Great British pounds, though the exchange rate varies!".