A sportsbook drops a "$100 bonus bet" in your account and it feels like $100 in your pocket. It isn't. A bonus bet is a shot at winning the profit on a bet, not the stake. That one detail cuts its real value roughly in half at standard odds.
Here's the whole thing, math first: how a bonus bet differs from cash, the formula for what one is actually worth, why longer odds keep more of that value, and the fine print (playthrough, expiry, restrictions) that turns "free" into something smaller.
- When a bonus bet wins, you get the profit only. The bonus stake is not returned.
- A bonus bet is worth roughly your true win probability times the profit: about $48 for a $100 bonus bet at a fair -110.
- Longer odds keep more of the bonus value, but they lose more often and every price still carries vig.
- Deposit-match offers with playthrough requirements make you bet real money first, and every one of those bets costs vig.
- "Free" is the marketing word. "Stake not returned" is the math.
What a bonus bet actually is
A bonus bet (books used to call them "free bets") is promotional credit you can wager but can't withdraw. You place it like any other bet. If it loses, it's gone and you're out nothing. If it wins, the book pays you the profit.
That sounds generous. It's also exactly why sportsbooks hand them out: bonus bets are a marketing cost designed to get you betting, depositing and coming back. We break down that side of it in how the sportsbook industry targets you. This post is about the mechanics and the math, so you can squeeze real value out of one without being steered by it.
Stake not returned: the detail that changes everything
With a cash bet, a win pays you the profit plus your stake back. With a bonus bet, a win pays the profit only. One major licensed book's help page puts it plainly: only the winnings come back, and the bonus stake is never returned to your wallet.
Cash bet wins: profit at -110 is $100 × (100 ÷ 110) = $90.91. You get back $190.91 ($100 stake + $90.91 profit).
Bonus bet wins: you get back $90.91. That's it.
Either one loses: the cash bet costs you $100. The bonus bet costs you $0.
Result: the best a $100 bonus bet at -110 can ever pay is $90.91.
So a "$100 bonus bet" can never put $100 of profit in your account unless you bet it at +100 or longer. And a win is never guaranteed.
What a bonus bet is really worth
Expected value is the right tool here, the same idea behind +EV betting. A bonus bet has two outcomes: win the profit, or lose nothing. So its value is simple:
If the price were perfectly fair (no vig), the true probability equals the implied probability of the odds, and the formula collapses into a handy shortcut:
Here's what that looks like for a $100 bonus bet at different prices, assuming each price is fair:
| Odds | Implied probability | Profit if it wins | Approx. value | Share of $100 kept |
|---|---|---|---|---|
| -110 | 52.4% | $90.91 | $47.62 | 48% |
| +100 | 50.0% | $100.00 | $50.00 | 50% |
| +200 | 33.3% | $200.00 | $66.67 | 67% |
| +300 | 25.0% | $300.00 | $75.00 | 75% |
| +500 | 16.7% | $500.00 | $83.33 | 83% |
| +1000 | 9.1% | $1,000.00 | $90.91 | 91% |
Real prices aren't fair. They include the vig, so your true win probability is a bit lower than the implied number, and the real value is a bit lower than the table.
You're looking at a $100 bonus bet on a +300 price. The table says $75 at a fair price.
But your honest estimate of the true probability is 23%, not 25%, because the book's margin is baked in.
0.23 × $300 = $69 of real value, not $75. Still a nice gift. Just not $100.
Why longer odds keep more value (to a point)
Look at the table again. The longer the odds, the bigger the profit relative to the stake, so losing the stake costs you less of the value. At -110 you keep about half. At +300 you keep about three-quarters.
So why not throw every bonus bet on a +2000 long shot? Three reasons:
- Variance. A +1000 bet loses about 10 times out of 11 at a fair price. If you only get one bonus bet, you'll most likely walk away with nothing. The value is real only over many bonus bets.
- Vig can be bigger on long shots. Futures and multi-outcome markets can hide more margin than a two-way line. Add up every option's implied probability. The further the total is above 100%, the more you're paying.
- It should still be a bet you'd make. A bonus bet doesn't turn a bad bet into a good one. It just changes who funded the stake.
A sensible middle ground: a plus-money price on a market where you can see both sides, check the vig, and still believe the bet is reasonable. Run it through the calculator before you click.
Bet-and-get vs. deposit match
Welcome offers come in a few common shapes. The names vary by book, but the mechanics repeat.
| Style | How it works | The catch |
|---|---|---|
| Bet-and-get | Place a qualifying cash bet, receive bonus bets. | Your qualifying bet is a real cash bet with normal vig. The bonus bets don't return their stake. |
| Second-chance / first-bet refund | If your first bet loses, the book refunds it, usually as bonus bets. | A refund in bonus bets is worth less than the same amount in cash. See the table above. |
| Deposit match | The book adds bonus funds equal to a percentage of your deposit. | Often comes with a playthrough requirement before related funds can be withdrawn. |
The pattern is always the same: the headline number is the bonus amount, and the real value is smaller.
The fine print: playthrough, expiry, restrictions
Playthrough (wagering) requirements
A playthrough requirement means you have to bet a set multiple of the bonus before related funds become withdrawable. That betting isn't free. Every bet carries vig.
Hypothetical: a $200 deposit-match bonus with a 5x playthrough. You must bet 5 × $200 = $1,000.
At -110 on coin-flip bets, every $110 risked loses $5 on average: (0.5 × $100) − (0.5 × $110) = −$5. That's about 4.55% of every dollar wagered.
$1,000 × 4.55% ≈ $45 in expected cost just to clear the requirement. Measure the bonus against that, not against $200.
Expiry dates
Bonus bets expire. One major licensed book's published terms say seven days unless an offer states otherwise. Other books and offers differ, so check the expiration date in your account. An expiring bonus is exactly how books push you into rushed, bad bets.
Restrictions
Read the offer's terms for limits like these:
- Sport- or bet-type-specific bonus bets (only for one sport, or only for a same-game parlay)
- Bet types that are excluded entirely
- Whether you can split one bonus bet across smaller wagers
- Whether you can combine several bonus bets on one wager
- Any minimum odds the offer requires
How to use a bonus bet with a plan
- Don't deposit more than your plan just to unlock a bigger bonus. Your unit size comes from your purse, not from a promo.
- Value it honestly. Use the shortcut: bonus × (1 − implied probability). That's your ceiling, not your floor.
- Pick a plus-money bet you'd actually make, on a market where you can check the vig.
- Run the numbers through the +EV Calculator using your own probability estimate.
- Log it as a bonus bet in your tracker, so your results stay honest.
- Move any winnings into your purse and treat them by the same three rules as everything else.
The bottom line: A bonus bet isn't $100. It's a chance at the profit on $100, worth about half that at -110 and more at longer odds. Value it with the formula, pick a sensible plus-money bet, and never let a promo change your purse or your unit size.
Frequently asked questions
How do bonus bets work?
A bonus bet lets you place a wager without risking your own cash. If it wins, you receive the profit only and the bonus stake is not returned. If it loses, you lose nothing but the bonus. Terms like expiry dates and eligible bet types vary by book.
Is a $100 bonus bet worth $100?
No. Because the stake isn't returned, a $100 bonus bet is worth roughly your true win probability times the profit. At a fair -110 price that's about $48, and at a fair +300 price it's about $75.
What odds should I use a bonus bet on?
Longer odds keep more of a bonus bet's value because the profit is bigger relative to the stake, but they lose more often and can carry more vig. A plus-money bet you would be comfortable making anyway, with the vig checked, is the sensible middle ground.
Do bonus bets expire?
Usually, yes. Each book sets its own expiry window, and at least one major licensed book's published terms say seven days unless an offer states otherwise. Check the expiration date in your account before you plan around it.
Can I withdraw a bonus bet?
No. The bonus itself can only be wagered. When a bonus bet wins, the profit is credited to your account, and from there the book's normal rules and any playthrough terms on the offer apply.
What is a playthrough requirement?
A playthrough or wagering requirement means you must bet a set multiple of the bonus before related funds can be withdrawn. A 5x playthrough on a $200 bonus means $1,000 in bets, and every one of those bets carries vig.
Run the bonus bet through the math.
Before you place it, plug the odds and your own probability into the BeginnerBets +EV Calculator — math, not gut feeling.
Open +EV Calculator →Disclaimer: BeginnerBets provides educational content only. All odds and offer amounts in this article are hypothetical, and promo terms vary by sportsbook and state; always read the current terms. Sports betting involves risk — never wager money you can't afford to lose. Sports betting is legal only in some states, and rules differ by state; check your state's law before you bet. Must be 21+ in most states. If you or someone you know has a gambling problem, call 1-800-GAMBLER or visit ncpgambling.org.