See what a bonus or free play is really worth after the rollover.
A free play pays winnings only, so it is worth less than cash before the rollover even starts. Bet at a standard -110 price it returns about 45% of face on average; underdog prices convert more of it because the winnings side is bigger.
Rollover is the total amount you must wager before you can withdraw. Every dollar of that handle passes through the book's margin, and that cost comes straight out of the bonus. This calculator nets the two numbers so you can see what an offer is actually worth.
It assumes a standard-hold market and no skill edge, so treat the result as a baseline. A 5x rollover on a small free play often survives the math; a 30x rollover on deposit plus bonus usually does not.
Strip the juice from any two-way line and see the fair price.
Check what a bet is worth given your odds and your win probability.
Combine up to eight legs and see the true payout and implied odds.
See how much margin the book has baked into a market.
Work out the hedge stake that locks in the same profit either way.
Size a bet from your edge and bankroll with the Kelly formula.