The fastest way to go broke sports betting is not picking the wrong teams. It is betting the wrong amounts. A bettor with a 55% win rate who bets 20% of their bankroll per game will go broke. A bettor with that same 55% win rate who bets 2% per game will build wealth steadily over thousands of bets. The math is unambiguous: bet sizing determines whether your edge compounds into profit or evaporates through variance.

Most sports bettors spend 95% of their time on handicapping and 5% on bankroll management. It should be closer to 50/50. Finding +EV bets is half the battle. Surviving the inevitable losing streaks long enough for your edge to manifest is the other half. This guide gives you the exact formulas, strategies, and frameworks to determine how much to bet per game, when to adjust your unit size, and how to survive the downswings that break undisciplined bettors.

Calculate your optimal bet size for any wager with our free Kelly Criterion Calculator.

Understanding Unit Sizing

What Is a Unit?

A unit is a standardized bet size expressed as a percentage of your total bankroll. Using units instead of dollar amounts keeps your bet sizing proportional to your bankroll regardless of whether you have $500 or $50,000.

Standard Unit Sizing:

Risk Level	Unit Size	$1,000 Bankroll	$5,000 Bankroll	$10,000 Bankroll
Conservative	1%	$10	$50	$100
Standard	2%	$20	$100	$200
Moderate	3%	$30	$150	$300
Aggressive	5%	$50	$250	$500
Reckless	10%+	$100+	$500+	$1,000+

Professional recommendation: 1-2% unit size for most bettors. Even highly skilled bettors with demonstrated edges rarely exceed 3%.

Why Unit Sizing Matters

Consider two bettors, both with a 55% win rate at -110 odds:

Bettor A: 10% unit size, $5,000 bankroll

Unit: $500
After a 10-game losing streak (which will happen eventually): Bankroll drops to $500
A 90% drawdown makes recovery nearly impossible
Risk of ruin: ~35% over 1,000 bets

Bettor B: 2% unit size, $5,000 bankroll

Unit: $100
After a 10-game losing streak: Bankroll drops to $4,000
A 20% drawdown is recoverable
Risk of ruin: ~0.5% over 1,000 bets

Same edge, radically different outcomes, purely because of bet sizing.

Track your bankroll variance and drawdowns with our Bankroll Volatility Tracker.

Flat Betting: The Simplest Strategy

How Flat Betting Works

Flat betting means wagering the same dollar amount on every bet, regardless of confidence level.

Rules:

Set your unit size (1-3% of bankroll)
Bet exactly one unit on every qualified bet
Periodically recalculate your unit as your bankroll changes (weekly or monthly)
Never deviate, regardless of results

Flat Betting Example

Starting bankroll: $5,000 Unit size: 2% = $100 Win rate: 54% at -110 odds

Over 500 bets:

270 wins x $90.91 profit = $24,545.70
230 losses x $100 cost = $23,000
Net profit: +$1,545.70
ROI: 3.1%

Advantages of Flat Betting

Simplicity: No complex calculations needed
Emotional control: Removes the temptation to chase or over-bet
Consistency: Predictable bankroll trajectory
Error-proof: Cannot accidentally over-expose on a single bet

Disadvantages of Flat Betting

Suboptimal growth: Does not capitalize on higher-edge bets
Does not adjust for edge size: A 10% edge bet gets the same stake as a 2% edge bet
Slower compounding: Fixed-size bets do not grow with the bankroll

Calculate the expected value of each bet to decide if it qualifies for your flat bet system with our Expected Value Calculator.

Kelly Criterion: The Mathematically Optimal Strategy

What Is the Kelly Criterion?

The Kelly Criterion is a formula that calculates the mathematically optimal bet size to maximize long-term bankroll growth. It was developed by John Kelly at Bell Labs in 1956 and has been used by professional gamblers, investors, and hedge fund managers ever since.

The Kelly Formula

Kelly % = (bp - q) / b

Where:

b = decimal odds - 1 (the profit multiple)
p = probability of winning
q = probability of losing (1 - p)

Kelly Criterion Examples

Example 1: Standard -110 Bet with 55% Edge

Odds: -110 (decimal 1.909)
b = 1.909 - 1 = 0.909
p = 0.55
q = 0.45

Kelly % = (0.909 x 0.55 - 0.45) / 0.909 Kelly % = (0.500 - 0.45) / 0.909 Kelly % = 0.050 / 0.909 Kelly % = 5.5% of bankroll

Example 2: Underdog at +200 with 38% Win Probability

Odds: +200 (decimal 3.00)
b = 3.00 - 1 = 2.00
p = 0.38
q = 0.62

Kelly % = (2.00 x 0.38 - 0.62) / 2.00 Kelly % = (0.76 - 0.62) / 2.00 Kelly % = 0.14 / 2.00 Kelly % = 7.0% of bankroll

Example 3: Heavy Favorite at -250 with 74% Win Probability

Odds: -250 (decimal 1.40)
b = 1.40 - 1 = 0.40
p = 0.74
q = 0.26

Kelly % = (0.40 x 0.74 - 0.26) / 0.40 Kelly % = (0.296 - 0.26) / 0.40 Kelly % = 0.036 / 0.40 Kelly % = 9.0% of bankroll

Run these calculations instantly with our Kelly Criterion Calculator.

The Problem with Full Kelly

Full Kelly is theoretically optimal but practically dangerous:

Assumes perfect probability estimates: If your 55% estimate is actually 52%, full Kelly will overbet catastrophically
Extreme volatility: Full Kelly bankrolls can swing 30-50% in short periods
Requires infinite bankroll divisibility: In practice, you cannot bet 7.3% of your bankroll precisely
No margin for error: Even a small systematic probability overestimation leads to ruin

Fractional Kelly: The Professional's Choice

Professional bettors universally use fractional Kelly, betting a fraction of the full Kelly recommendation:

Kelly Fraction	Description	Best For
1/4 Kelly	Very conservative	New bettors, uncertain edges
1/3 Kelly	Conservative	Most recreational +EV bettors
1/2 Kelly	Standard professional	Experienced bettors with proven records
2/3 Kelly	Aggressive	Bettors with very large sample sizes
Full Kelly	Maximum growth	Theoretically optimal, practically dangerous

Example: 1/2 Kelly Application

Using Example 1 above (5.5% full Kelly):

1/2 Kelly = 2.75% of bankroll
On a $10,000 bankroll: $275 per bet

This sacrifices approximately 25% of theoretical growth rate for a massive reduction in variance and risk of ruin.

Understand how vig impacts your edge calculation with our Hold/Vig Calculator.

How Much Bankroll Do You Need?

Bankroll Requirements by Bet Volume

The minimum bankroll depends on how many bets you plan to make and your unit size:

Bets Per Month	Unit Size	Minimum Bankroll (to survive variance)
20-30	2%	50 units ($2,500 if $50/bet)
50-100	2%	75 units ($3,750 if $50/bet)
100-200	2%	100 units ($5,000 if $50/bet)
200+	1-2%	150+ units ($7,500+ if $50/bet)

Why 50-100 Units Is the Minimum

The math behind minimum bankroll requirements comes from downswing probability:

With a 55% win rate at -110:

Probability of a 10-bet losing streak: 0.034% (happens ~once per 3,000 bets)
Probability of a 15-unit drawdown: ~5% over 1,000 bets
Probability of a 25-unit drawdown: ~1% over 1,000 bets
Probability of a 40-unit drawdown: ~0.1% over 1,000 bets

If your bankroll is only 20 units, a 15-unit drawdown wipes out 75% of your capital. With 100 units, the same drawdown is only 15%, easily survivable.

Assess your risk of ruin based on your bankroll with our Poker Risk of Ruin Calculator, which applies the same mathematics to any bankrolled pursuit.

Bankroll by Skill Level

Bettor Profile	Win Rate	Recommended Bankroll	Reasoning
Beginner (+EV)	52-53%	100+ units	Thin edge, high variance
Intermediate	54-55%	75+ units	Moderate edge, manageable variance
Advanced	56-58%	50+ units	Strong edge, faster recovery
Professional	58%+	50-100+ units	Volume compensates

Surviving Downswings

What Downswings Look Like

Even the best sports bettors experience significant drawdowns. Understanding the math prevents panic:

55% Win Rate Bettor, 1,000 Bets, 2% Unit Size:

Drawdown Size	Probability	Units Lost	Impact on $10K Bankroll
10 units	~30%	10	$9,000 (-10%)
20 units	~10%	20	$8,000 (-20%)
30 units	~2%	30	$7,000 (-30%)
40 units	~0.5%	40	$6,000 (-40%)
50 units	~0.1%	50	$5,000 (-50%)

A 20% drawdown is almost guaranteed at some point. A 30% drawdown happens to 1 in 50 bettors with a genuine edge. These are not signs of failure; they are statistical inevitabilities.

How to Handle Drawdowns

Rule 1: Do Not Increase Bet Size The worst response to a losing streak is betting more to recover faster. Maintain your unit size. If anything, decrease your unit size during drawdowns to protect remaining capital.

Rule 2: Reassess, Do Not Abandon A drawdown is the right time to review your handicapping, not to abandon your strategy. Check:

Are you still getting positive CLV?
Has your market or sport changed fundamentally?
Is the drawdown within normal statistical variance?

Rule 3: Trust the Process If CLV Is Positive If your Closing Line Value is positive through the drawdown, your strategy is working. Variance has not shifted in your favor yet, but it will. Continue making the same +EV bets at the same unit size.

Rule 4: Step Down When Needed If your drawdown exceeds 30% of your bankroll:

Reduce unit size from 2% to 1.5% or 1%
Continue betting but with reduced exposure
Rebuild the unit size as the bankroll recovers

Monitor your drawdowns and recovery with our Bankroll Volatility Tracker.

When to Move Up in Stakes

Criteria for Increasing Unit Size

Increase your unit size (or total bankroll allocation) only when:

Proven edge over 500+ bets: Your CLV and ROI demonstrate a genuine, sustained edge
Bankroll has grown significantly: Your unit as a percentage of bankroll can stay the same while the dollar amount grows naturally
Emotional readiness: You can handle larger dollar swings without deviating from strategy
No lifestyle pressure: Your bankroll is still money you can afford to lose entirely

The Right Way to Scale

Approach 1: Percentage-Based Scaling (Recommended) Keep your unit at 2% of bankroll. As the bankroll grows, your bet size grows automatically:

Start: $5,000 bankroll, $100 unit
Month 3: $5,800 bankroll, $116 unit
Month 6: $6,500 bankroll, $130 unit
Year 1: $8,000 bankroll, $160 unit

Approach 2: Step-Function Scaling Increase unit size at defined bankroll milestones:

Bankroll Level	Unit Size	Dollar Amount
$5,000	2%	$100
$7,500	2%	$150
$10,000	2%	$200
$15,000	2%	$300
$25,000	2%	$500

When to Move Down

Reduce your unit size when:

Your bankroll drops 25%+ from peak
You lose confidence in your edge (CLV turns negative)
Life circumstances change (you can afford to lose less)
You enter a new sport or market type where your edge is unproven

Real-World Bankroll Management Scenarios

Scenario 1: The Conservative Grinder

Profile: $5,000 bankroll, 54% win rate, 100 bets/month at -110 Unit size: 1.5% ($75)

Monthly expected results:

54 wins x $68.18 = $3,681.82
46 losses x $75 = $3,450
Monthly profit: +$231.82
Monthly ROI: 3.1%

Annual projection: +$2,781.84 (55.6% return on bankroll)

After year 1 with reinvestment:

Bankroll grows from $5,000 to ~$7,782
Unit grows from $75 to ~$117

This is sustainable, boring, and profitable. Professional betting is rarely exciting.

Scenario 2: The Kelly Bettor

Profile: $10,000 bankroll, variable edges, 60 bets/month Strategy: 1/3 Kelly on every qualified bet

Sample month:

15 bets at 3% edge: 1/3 Kelly = 1.1% per bet ($110)
25 bets at 5% edge: 1/3 Kelly = 1.8% per bet ($180)
10 bets at 8% edge: 1/3 Kelly = 2.9% per bet ($290)
10 bets at 2% edge: 1/3 Kelly = 0.7% per bet ($70)

Monthly expected profit:

(15 x $110 x 0.03) + (25 x $180 x 0.05) + (10 x $290 x 0.08) + (10 x $70 x 0.02)
$49.50 + $225 + $232 + $14
Monthly expected profit: +$520.50
Monthly ROI: 4.2% (on total amount wagered)

Kelly sizing allocates more capital to higher-edge bets, improving overall returns versus flat betting.

Scenario 3: The Underfunded Beginner

Profile: $500 bankroll, unknown edge, starting out Unit size: 1% ($5)

This bankroll is too small for meaningful profit but appropriate for learning:

Track every bet meticulously
Focus on developing your handicapping skills
After 300+ tracked bets, assess your edge
Only increase bankroll once you have demonstrated +EV and positive CLV

Calculate the implied probability of any line you are considering with our Implied Probability Calculator.

Scenario 4: The Downswing Survivor

Profile: $8,000 bankroll (started at $10,000), 25-unit drawdown over 3 months Original unit: 2% ($200) Adjusted unit: 1.5% ($120)

The bettor has positive CLV (+2.5%) through the drawdown. The math says:

Expected recovery time: 150-250 bets at +2.5% CLV
At 80 bets/month: 2-3 months to recover
Reduced unit size protects against further drawdown
As bankroll recovers above $9,000, gradually increase unit back to 2%

This is the disciplined approach. The undisciplined approach (doubling unit size to recover faster) leads to ruin.

Comparing Bankroll Strategies

Flat Betting vs. Kelly Criterion vs. Percentage Betting

Feature	Flat Betting	Kelly Criterion	Percentage of Bankroll
Complexity	Low	High	Medium
Growth rate	Moderate	Highest (theoretical)	Good
Variance	Moderate	High (full Kelly)	Low
Error tolerance	High	Low	High
Best for	Beginners, grinders	Experienced, data-rich	Most bettors
Risk of ruin	Low	Medium-High (full)	Low
Adapts to edge?	No	Yes	No
Adapts to bankroll?	No (manual)	Yes	Yes

Recommendation by Bettor Type

Recreational with positive edge: Flat betting at 1-2% per bet. Simple, effective, low risk.

Serious with 500+ tracked bets: 1/3 Kelly with a 2% cap on any single bet. Balances growth optimization with risk management.

Professional with 2,000+ tracked bets: 1/2 Kelly with a 3% cap. Proven edge justifies more aggressive sizing, but never full Kelly.

Calculate optimal Kelly sizing with our Kelly Criterion Calculator.

Advanced Bankroll Concepts

Simultaneous Bet Exposure

When you have multiple bets pending simultaneously, your total exposure matters:

5 bets of 2% each = 10% of bankroll at risk simultaneously
If all 5 lose (correlated events like all NFL Sunday games): 10% drawdown in one day

Rule: Total outstanding exposure should not exceed 10-15% of your bankroll. This may mean reducing individual bet sizes on high-volume days.

Correlated Bet Risk

Bets on the same sport, same day, or related outcomes are correlated. Three NFL bets on the same Sunday are not three independent events; weather, referee tendencies, and league-wide trends create correlation.

Mitigation:

Limit to 3-5 bets on any single day
Diversify across sports when possible
Account for correlation when calculating total exposure

Stale Bankroll Calculation

If your bankroll has not changed in months despite consistent betting, your edge may be zero. Reassess:

Are you break-even? (edge = vig, net zero)
Is your sample size large enough?
Have market conditions changed?

Understand how market vig impacts your bottom line with our Hold/Vig Calculator.

Reserve Bankroll

Professional bettors maintain a reserve (money not currently allocated to betting) for:

Reloading after significant drawdowns
Capitalizing on new opportunities (new sportsbook promotions)
Maintaining betting volume during downswings

Recommended structure:

Active bankroll: 60-70% of total gambling capital
Reserve: 30-40% of total gambling capital

Cross-Sport Bankroll Allocation

If you bet multiple sports, consider separate sub-bankrolls:

Sport	Edge Confidence	Bankroll Allocation
NFL (your strongest)	High	40%
NBA	Moderate	25%
MLB	Moderate	20%
NHL	Lower	10%
Other	Experimental	5%

This prevents poor performance in one sport from destroying your entire bankroll.

Compare your risk of ruin across different bankroll levels with our Blackjack Risk of Ruin Calculator, which uses the same mathematical framework applicable to any bankrolled gambling pursuit.

The Mathematics of Bankroll Growth

Compound Growth with Fixed Percentage

When you bet a fixed percentage of your bankroll, wins and losses compound:

Growth Formula: Bankroll_n = Bankroll_0 x (1 + r)^n

Where:

r = average return per bet (positive if +EV)
n = number of bets

Example:

$5,000 starting bankroll
+2% average return per bet (after vig)
1,000 bets per year

Bankroll after 1 year: $5,000 x (1.001)^1,000 = $5,000 x 2.717 = $13,585

Note: This assumes 0.1% per bet at a 2% unit size with +5% ROI. Actual results will vary significantly due to variance.

The Asymmetry of Losses

Losses hurt more than wins help:

A 50% drawdown requires a 100% gain to recover
A 25% drawdown requires a 33% gain to recover
A 10% drawdown requires an 11% gain to recover

This asymmetry is why conservative bet sizing is so critical. Preventing large drawdowns is more valuable than maximizing growth during winning streaks.

Convert any odds format to calculate your exact risk with our Odds Converter.

Frequently Asked Questions

How much should I bet per game on sports? Most professionals recommend 1-3% of your bankroll per bet. A 2% unit size is the sweet spot for most bettors: aggressive enough to generate meaningful profit, conservative enough to survive inevitable losing streaks. Use our Kelly Criterion Calculator to calculate the optimal amount based on your specific edge.

What is the Kelly Criterion in sports betting? The Kelly Criterion is a mathematical formula that calculates the optimal percentage of your bankroll to bet based on your estimated edge. The formula is: Kelly % = (bp - q) / b, where b is the decimal odds minus 1, p is your win probability, and q is your loss probability. Most professionals use fractional Kelly (1/4 to 1/2) for safety.

How big should my sports betting bankroll be? At minimum, 50 units (50x your standard bet size). For serious bettors, 100+ units is recommended. If you bet $100 per game, you should have at least $5,000-$10,000 dedicated to sports betting. Monitor your bankroll health with our Bankroll Volatility Tracker.

What is the difference between flat betting and Kelly Criterion? Flat betting means wagering the same amount on every bet regardless of edge size. The Kelly Criterion varies your bet size based on your estimated edge: larger bets when your edge is bigger, smaller bets when it is thinner. Flat betting is simpler and more error-tolerant; Kelly maximizes theoretical growth but requires accurate probability estimates.

How do I survive a losing streak in sports betting? Maintain your standard unit size (do not increase bets to chase losses). If the drawdown exceeds 25-30% of your bankroll, reduce your unit size by 25-50%. Verify your edge still exists by checking your Closing Line Value. If CLV is positive, the losing streak is variance, not a broken strategy. Use our Expected Value Calculator to verify your bets are still +EV.

Should I use a variable bet sizing system? Only if you have reliable probability estimates and a proven track record over 500+ bets. Variable sizing (like Kelly) is more profitable than flat betting in theory, but if your probability estimates are inaccurate, it amplifies your mistakes. Start with flat betting, track your results, and graduate to fractional Kelly once you have confidence in your edge estimates.

How often should I recalculate my unit size? Recalculate weekly or monthly, depending on your betting volume. With percentage-based betting, your unit adjusts automatically as your bankroll grows or shrinks. With flat betting, manually recalculate at set intervals. Use our Implied Probability Calculator to ensure your edge estimates remain accurate.

Can I use the same bankroll for multiple sports? Yes, but track performance by sport separately. Your edge may differ significantly across sports. Consider sub-allocating your bankroll if one sport consistently underperforms. Use our Poker Bankroll Requirements Calculator to understand bankroll requirements for any bankrolled gambling discipline.

Essential Bankroll Management Tools

Bet Sizing and Optimization

Kelly Criterion Calculator: Calculate the mathematically optimal bet size for any wager
Expected Value Calculator: Determine if a bet qualifies for your bankroll system
Implied Probability Calculator: Convert odds to probabilities for edge estimation

Bankroll Tracking and Risk

Bankroll Volatility Tracker: Monitor bankroll swings, drawdowns, and recovery
Poker Risk of Ruin Calculator: Calculate your probability of going broke given your edge and bankroll
Blackjack Risk of Ruin Calculator: Apply risk-of-ruin mathematics to any bankrolled endeavor

Odds Analysis

Odds Converter: Convert between American, decimal, and fractional odds
Hold/Vig Calculator: Calculate the sportsbook's margin on any line
Hedge Calculator: Calculate hedge amounts to lock in profit and manage risk

The Bottom Line

Sports betting bankroll management is not glamorous, but it is the difference between long-term profit and inevitable ruin. The formula is straightforward:

Set your bankroll: Money you can afford to lose entirely
Define your unit: 1-3% of bankroll per bet
Bet consistently: Flat betting or fractional Kelly
Track everything: Bets, results, CLV, drawdowns
Adjust slowly: Only increase stakes with proven, sustained edge
Survive drawdowns: Reduce sizing during bad stretches, never increase
Compound over time: Small edges + proper sizing = significant returns

The bettors who last long enough to realize their edge are the bettors who manage their money properly. Everyone else goes broke, regardless of how well they handicap.

Start managing your bankroll with our free Kelly Criterion Calculator. Track your performance with our Bankroll Volatility Tracker. And verify your bets are +EV with our Expected Value Calculator.

Your edge means nothing if your bankroll does not survive long enough to prove it.

Gambling involves risk. This content is for educational and informational purposes only. Always gamble responsibly, set limits you can afford, and seek help if gambling becomes a problem. Visit the National Council on Problem Gambling or call 1-800-522-4700 for support.