Betting Unit Calculator
Calculate optimal betting unit size from bankroll and risk tolerance. Enter values for instant results with step-by-step formulas.
Formula
Unit Size = Bankroll x (Unit Percentage / 100)
Your unit size is a fixed percentage of your total bankroll. The expected profit per bet is (Win Rate x Profit Per Win) - ((1 - Win Rate) x Unit Size). ROI equals expected profit divided by unit size. A positive ROI with proper unit sizing ensures sustainable long-term growth.
Worked Examples
Example 1: Standard Bankroll Setup
Problem: You have a $2,000 bankroll and want to use 2% units. Your win rate is 55% at average odds of -110 (1.91 decimal). What is your unit size and expected performance?
Solution: Unit size = $2,000 x 0.02 = $40\nProfit per win = $40 x (1.91 - 1) = $36.40\nLoss per loss = $40\nEV per bet = (0.55 x $36.40) - (0.45 x $40) = $20.02 - $18.00 = $2.02\nROI = $2.02 / $40 = 5.05%\nPer 100 bets: $2.02 x 100 = $202 expected profit\nBankroll has 50 units of runway
Result: Unit: $40 | EV: +$2.02/bet | ROI: 5.05% | 50 units in bankroll
Example 2: Confidence-Based Unit System
Problem: With a $5,000 bankroll at 1% base units, calculate stake sizes for a 4-tier confidence system (0.5x, 1x, 1.5x, 2x).
Solution: Base unit = $5,000 x 0.01 = $50\nLow confidence (0.5 unit) = $25\nStandard confidence (1 unit) = $50\nHigh confidence (1.5 units) = $75\nMax confidence (2 units) = $100\nBankroll contains 100 base units\nMax exposure per bet = 2% ($100)\nAt 55% win rate with -110 odds:\nExpected profit per standard unit = $2.55
Result: Low: $25 | Standard: $50 | High: $75 | Max: $100 | 100 units deep
Frequently Asked Questions
What is a betting unit and why should I use unit-based betting?
A betting unit is a standardized amount that represents a fixed percentage of your total bankroll, used to normalize bet sizes and track performance consistently. Instead of betting random dollar amounts, unit-based betting ensures you risk a proportional amount relative to your bankroll size. This approach protects you from over-betting during emotional moments, provides clear performance tracking in units won or lost, and automatically adjusts your bet sizes as your bankroll grows or shrinks. Professional bettors universally use unit-based systems because it enforces discipline and makes it possible to compare performance across different bankroll sizes.
How do I determine the right unit size for my bankroll?
The right unit size depends on your risk tolerance, edge size, and betting style. The most common recommendation is 1 to 3 percent of your bankroll per unit. Conservative bettors use 1 percent, which allows for 100 units of cushion before going bust. Standard bettors typically use 2 percent, providing 50 units of runway. Aggressive bettors might use 3 to 5 percent, but this increases the risk of ruin significantly during inevitable losing streaks. A good rule of thumb is that your unit size should be small enough that losing 10 consecutive bets does not significantly impact your ability to continue betting. Start smaller and adjust as you gain confidence in your edge.
What is flat betting versus percentage betting?
Flat betting means wagering the same fixed dollar amount on every bet regardless of your current bankroll size. Percentage betting adjusts your bet size based on your current bankroll, so the dollar amount changes as your bankroll fluctuates. Flat betting is simpler but does not adapt to bankroll changes, meaning you could be over-betting a declining bankroll or under-betting a growing one. Percentage betting automatically scales, protecting you during downswings and maximizing growth during upswings. Most professionals use percentage-based units because the mathematical advantages of dynamic sizing compound over time and significantly reduce the probability of ruin.
Should I vary my unit size based on confidence level?
Many successful bettors use a tiered confidence system where they bet 0.5 units on low-confidence plays, 1 unit on standard plays, 1.5 units on high-confidence plays, and 2 units on maximum confidence plays. However, this approach requires honest self-assessment and discipline. Research has shown that most bettors overestimate their confidence on large bets and the highest-confidence plays do not always have the highest win rates. If you choose to vary unit sizes, track your results by confidence tier to verify that your bigger bets actually perform better. If they do not, revert to flat unit sizing to protect your bankroll from overconfidence bias.
How do I track my betting performance in units?
Track every bet with the date, event, odds, stake in units, result, and running unit profit or loss. Your key metrics should include total units won or lost, win rate percentage, average odds, ROI per unit, and closing line value. Use a spreadsheet or dedicated tracking app to maintain these records. Express all results in units rather than dollars so you can evaluate performance independently of bankroll size. A bettor who is up 20 units on a 100-unit bankroll has achieved a 20 percent return, which is the same performance whether the bankroll was $1,000 or $100,000. Review your records monthly to identify patterns and adjust your strategy.
What is the relationship between unit size and risk of ruin?
Risk of ruin is the probability of losing your entire bankroll, and it is directly related to unit size. Larger units dramatically increase ruin probability. With a 55 percent win rate at -110 odds, the risk of ruin for various unit sizes is approximately: 1 percent units = less than 0.1 percent risk, 2 percent units = about 1 percent risk, 5 percent units = about 15 percent risk, and 10 percent units = about 40 percent risk. These numbers show why professional bettors keep units small. Even with a genuine edge, betting too large a percentage of your bankroll per wager creates an unacceptable probability of going broke before your edge has time to manifest.