Size for CFDs means total contract value (number of contracts x value per contract).
Closing price means underlying market price when underlying market closes.
If your trade is in GBP
Size × closing price × LIBOR +/- 2.5% ÷ 365 Based on LIBOR one month overnight rate
If your trade is in USD
Size × closing price × US LIBOR +/–2.5% ÷ 360
If your trade is in EUR
Size × closing price × EURIBOR +/–2.5% ÷ 360
Please note: when trading a non-standard GBP-denominated index CFD, or a mini contract on any asset class, the funding rate is +/-3% rather than +/-2.5%