Use our odds calculator to make risk free profit at bet exchanges. your back stake with the bookmaker and the lay stake with the exchange such as Betfair. You are here: Home >> Tools >> Online Calculators >> Betfair Hedging Calculator. Introduction. This online tool calculates various strategies when a hedging. Calculate level-profit stakes for Back/Lay betting (arbing and trading) in same- market or cross-market betting. The site also explains Back/Lay arbitrage and.