Betfair Calculator. Easily calculate your back and lay odds on betting exchange sites such as Betfair, Betdaq and WBX. Betting on betting exchange websites. If you've had a bet and it's shortened in price, use this calculator to see how you can guarantee yourself a profit using the betting exchanges - win or lose. Our bet calculator will help you quickly determine your matched betting profits. Use our odds calculator to make risk free profit at bet exchanges.