Free Bet Calculator: How to Convert Free Bets Into Guaranteed Profit
Free bet calculator math for converting bonus bets at 70-80% rates. Learn the SNR conversion formula, 2 worked examples, and 5 mistakes that destroy your edge.
What a Free Bet Calculator Does
A free bet calculator converts bonus bets into guaranteed cash. Sportsbooks hand out free bets as promotions: sign-up bonuses, reload offers, risk-free first bets. The catch is you cannot withdraw them directly. You need to wager them first. The math determines exactly how much real money you can extract from every free bet, regardless of which team wins.
The core concept: place the free bet on one side of a market, then hedge the other side with your own cash on a different sportsbook. One side wins, the other loses. The net result is a guaranteed profit. A free bet conversion calculator automates the arithmetic, but understanding the formula matters more than any tool.
Typical conversion rates land between 70% and 80%. A $100 free bet becomes $70 to $80 in real cash. Anything below 65% means you picked bad odds. Anything above 80% means you found an excellent line discrepancy between books.
The SNR Free Bet Conversion Formula
Most free bets are "stake not returned" (SNR). You receive the profit if the free bet wins, but the stake itself is not included in the payout. This changes the math compared to a normal bet.
Here is the SNR conversion process:
- Find a market with wide odds discrepancy between two sportsbooks.
- Place the free bet on the underdog (plus-money side) at Book A.
- Place a real-money hedge bet on the opposite side at Book B.
- Calculate the hedge amount so your profit is equal regardless of outcome.
The hedge formula for SNR free bets:
Hedge Stake = (Free Bet Amount x Free Bet Decimal Odds - Free Bet Amount) / Hedge Decimal Odds
Wait. That is the simplified version. The precise formula that equalizes profit across both outcomes:
Hedge Stake = (Free Bet x (Decimal Odds - 1)) / Hedge Decimal Odds
Guaranteed Profit = Free Bet x (Decimal Odds - 1) - Hedge Stake
If you need to convert American odds to decimal for this formula, use the odds converter. The relationship is straightforward: +200 American = 3.00 decimal, -150 American = 1.667 decimal. See our full guide on how to read odds for the conversion math.
Worked Example 1: Converting a $200 Free Bet
You receive a $200 SNR free bet from DraftKings. You find an NFL moneyline:
- DraftKings: Cowboys +250 (decimal 3.50)
- FanDuel: Eagles -260 (decimal 1.385)
Step 1: Calculate the free bet payout if it wins.
Free bet profit if Cowboys win = $200 x (3.50 - 1) = $200 x 2.50 = $500
Remember: SNR means the $200 stake is not returned. You only get the $500 profit.
Step 2: Calculate the hedge stake.
Hedge Stake = $500 / 1.385 = $361.01
Step 3: Calculate the guaranteed profit for each outcome.
If Cowboys win (free bet wins):
- Free bet profit: +$500
- Hedge bet loss: -$361.01
- Net profit: +$138.99
If Eagles win (hedge wins):
- Free bet loss: $0 (it was a free bet, no real money lost)
- Hedge bet profit: $361.01 x 1.385 - $361.01 = $500.00 - $361.01 = +$138.99
Both outcomes produce $138.99 in profit. That is a 69.5% conversion rate on the $200 free bet.
The conversion rate formula: (Guaranteed Profit / Free Bet Amount) x 100
$138.99 / $200 = 69.5%
A 69.5% rate is acceptable but not great. Better odds would push this higher. Let us look at an optimized example.
Worked Example 2: Maximizing Conversion Rate With Better Lines
Same $200 free bet, but you shop harder and find:
- DraftKings (free bet): Nuggets +320 (decimal 4.20)
- BetMGM (hedge): Celtics -330 (decimal 1.303)
Free bet profit if Nuggets win: $200 x (4.20 - 1) = $200 x 3.20 = $640
Hedge Stake: $640 / 1.303 = $491.17
If Nuggets win:
- Free bet profit: +$640
- Hedge loss: -$491.17
- Net: +$148.83
If Celtics win:
- Free bet loss: $0
- Hedge profit: $491.17 x 1.303 - $491.17 = $640.00 - $491.17 = +$148.83
Conversion rate: $148.83 / $200 = 74.4%
The difference: finding +320/-330 instead of +250/-260 added $9.84 in guaranteed profit. That 5 percentage point improvement came purely from line shopping. On a $1,000 free bet, the same improvement would mean an extra $49.20 in guaranteed cash.
This is why experienced bettors check 4 to 6 sportsbooks before converting. The EV calculator helps identify which lines offer the most value across different books.
Stake-Returned vs. Stake-Not-Returned Free Bets
Not all free bets work the same way. The two types require different math.
SNR (Stake Not Returned): The most common type. If your free bet wins, you receive only the profit portion. The free bet stake disappears regardless of outcome. This is what Examples 1 and 2 above cover. Typical conversion: 70-80%.
SR (Stake Returned): Rarer and more valuable. If your free bet wins, you receive both the profit and the original stake amount as withdrawable cash. The conversion math changes because the winning payout is higher.
For SR free bets, the hedge formula adjusts:
Hedge Stake = (Free Bet x Decimal Odds) / Hedge Decimal Odds
Using Example 1's numbers with SR instead of SNR:
- Free bet payout if win: $200 x 3.50 = $700 (stake included)
- Hedge Stake: $700 / 1.385 = $505.42
- Profit either way: $700 - $505.42 = $194.58
- Conversion rate: 97.3%
SR free bets convert at 90-100%. If you receive one, prioritize converting it immediately. They are significantly more valuable than SNR bets.
Always check the terms. The sportsbook's promotion page will specify "bonus bet" (usually SNR) or "free bet with stake returned" (SR). Misidentifying the type will cause your hedge math to be wrong, and one outcome will produce a loss instead of the guaranteed profit you expected.
5 Common Mistakes That Kill Your Conversion Rate
1. Betting favorites with the free bet. Place the free bet on the plus-money side, always. A free bet on -200 (decimal 1.50) only generates $100 profit on a $200 stake. A free bet on +200 (decimal 3.00) generates $400 profit on the same $200 stake. Higher potential profit means more of the free bet converts to cash.
2. Ignoring the qualifying bet cost. Many promotions require a qualifying bet before the free bet is issued. If you place a $500 qualifying bet and lose $25 on the vig, your $200 free bet conversion drops from $148 to $123 in net profit. Always account for qualifying losses. Use the EV calculator to model the full promotion lifecycle.
3. Using the same sportsbook for both sides. Sportsbooks monitor hedging behavior. Placing opposite sides of the same game on the same book is a fast way to get your account limited or your bonus voided. Always hedge on a different sportsbook.
4. Converting on low-liquidity markets. Obscure prop bets might show big line discrepancies, but they also carry the risk of bet cancellation or void. Stick to major markets: moneylines, spreads, and totals on major sports. The lines are tighter but the execution is reliable.
5. Waiting too long. Free bets expire. Most sportsbook bonuses have a 7 to 14 day window. Lines also move. The +320 you spotted at 9 AM might be +280 by game time. Convert early, and convert on games with stable lines.
Understanding expected value helps you evaluate whether a promotion is worth pursuing at all. Some sign-up offers have negative EV after accounting for all costs.
Optimal Conversion Rates and When to Pull the Trigger
Not every conversion is worth executing. Here are the benchmarks:
| Conversion Rate | Assessment |
|---|---|
| Below 60% | Poor. Wait for better lines. |
| 60-70% | Acceptable if the free bet expires soon. |
| 70-75% | Good. Standard for most conversions. |
| 75-80% | Very good. Convert immediately. |
| Above 80% | Excellent. Rare, usually from line errors. |
The math is simple, but the execution requires line shopping discipline. Bettors who track lines across multiple books using tools like the odds converter consistently achieve higher conversion rates.
For proper bankroll management during free bet conversions, the Kelly Criterion framework helps you understand position sizing on the hedge side. While free bet conversions are technically risk-free (the free bet side costs nothing), the hedge side uses real money from your bankroll. Read the full Kelly Criterion guide for sizing principles.
If you are looking for ongoing edge after you have burned through sign-up bonuses, live arbitrage betting uses similar two-sided hedging logic but on live in-game markets where pricing inefficiencies appear frequently.
Frequently asked questions
- What is a good free bet conversion rate?
- A good conversion rate is 70-80%. This means a $100 free bet converts to $70-$80 in guaranteed cash. Below 65% is poor, and you should shop for better lines. Above 80% is excellent and usually results from significant line discrepancies between sportsbooks.
- Should I bet the free bet on favorites or underdogs?
- Always bet the free bet on underdogs (plus-money odds). SNR free bets only pay the profit portion, so higher odds generate a larger potential payout. Betting a free bet on a -200 favorite only produces $100 profit on a $200 stake, while +200 produces $400.
- What is the difference between SNR and SR free bets?
- SNR (stake not returned) free bets pay only the profit if they win. The stake disappears. SR (stake returned) free bets pay the profit plus the stake as withdrawable cash. SR bets convert at 90-100% vs. 70-80% for SNR. Always check which type your sportsbook offers.
- Can sportsbooks void my free bet for hedging?
- Sportsbooks generally cannot detect hedging across different platforms. However, placing both sides on the same book is easily detected and can result in bonus forfeiture or account limitation. Always use a different sportsbook for the hedge bet.
- How long do I have to use a free bet?
- Most free bets expire within 7 to 14 days of being credited. Some promotions give as little as 24 hours. Check the terms immediately when you receive a free bet and convert it early to avoid expiration and line movement.