// 4 modes · monte carlo · ruin live
Bankroll Calculator & Risk-of-Ruin Planner(2026)
Universal bankroll planner for sports betting, blackjack, poker and video poker. Live Monte Carlo simulation, multi-strategy comparison, and real-time risk-of-ruin readout. Built by an iGaming engineer who actually risks their own money on these numbers.
Choose your context
Variance presets, edge units, and ruin formulas adapt automatically
Quick presets
Four realistic player profiles. One click loads the inputs.
Disposable income only — money you can lose without changing your life
Your expected long-run advantage. Use 0 if unsure.
Used for sports mode. Typical price you take.
Higher variance widens swings and raises ruin probability.
How many bets/hands/sessions you plan to play.
Multi-strategy side-by-side
Same inputs, four sizing methods. See how unit, ruin and ROI shift.
| Method | Unit | Ruin | Double | Verdict |
|---|---|---|---|---|
| Flat % | $20.00 | <0.1% | 2,311 | Safe |
| Units (1% standard) | $10.00 | <0.1% | 4,621 | Safe |
| Fractional Kelly | $8.24 | <0.1% | 5,607 | Safe |
| Full Kelly | $16.48 | <0.1% | 2,804 | Safe |
Monte Carlo bankroll trajectories
100 simulated paths. Median in bold, 5th/95th percentile dashed. Live, runs in your browser.
Bankroll tier ladder
Click any tier to apply its unit size to inputs.
What is a bankroll calculator
A bankroll calculator is a tool that works out how much you should stake per bet so you don't go broke over the long run. Your bankroll is the money you've set aside specifically for gambling, and a unit is your base stake, typically a percentage of that bankroll. The calculator takes your bankroll, your risk profile, and your win rate, then tells you your unit size, your risk of ruin, and how your bankroll is likely to grow or shrink.
The core idea behind bankroll management is straightforward: keep each stake small relative to your total bankroll, and a bad run won't wipe you out. Bet 50% of your bankroll on a single wager and two losses in a row leave you with almost nothing. Bet 1-2% per wager and even ten consecutive losses still leave you with money on the table and a real chance to recover. The calculator turns that logic into concrete numbers tailored to your bankroll.
Under the hood, the tool runs a Monte Carlo simulation, running your strategy through thousands of randomised sequences to find out what percentage of scenarios end in your bankroll hitting zero. That percentage is your risk of ruin. The calculator also compares strategies side by side, flat staking, quarter-Kelly, and full Kelly, so you can see exactly what separates a cautious approach from an aggressive one.
One thing worth understanding: your bankroll is not your entire account balance. It's a dedicated gambling fund, money you can afford to lose. The most common beginner mistake is treating the whole balance as the bankroll and recalculating percentages after every win or loss. The calculator helps you lock in a starting bankroll and make decisions based on that number, not on how you're feeling in the moment.
Flat staking vs. the Kelly criterion
This is an important choice. Flat betting means a fixed unit every time, say 1% of your bankroll. It's simple, predictable, and safe. The Kelly criterion is mathematically optimal for long-run growth, but it's aggressive and the drawdowns are brutal. Full Kelly can comfortably cut your bankroll in half on the way up. Quarter-Kelly is a sensible middle ground, capturing most of the growth with significantly less pain. Over the long run, discipline and an honest win rate matter more than the formula you use.
How to use the bankroll calculator
In about a minute you'll have your recommended unit size and risk of ruin across thousands of simulated runs.
Step 1. Enter your bankroll and risk profile
Type in the amount you're setting aside for gambling, money that isn't rent money or borrowed, and choose a risk profile: conservative, moderate, aggressive, or maximum. Your profile determines what percentage of your bankroll goes on each unit, anywhere from 0.5% up to full Kelly. You can also just click a tier in the ladder below and the calculator will fill in your unit size automatically.
Step 2. Add your win rate and odds
Enter your real win rate and your average odds. Be honest here. An inflated win rate produces numbers that look great but are completely misleading, and your risk of ruin will be understated as a result. If you're not sure of the exact figure, use a conservative estimate. It's far better to underestimate your edge than to overestimate it.
Step 3. Read your risk of ruin and Monte Carlo results
The calculator will show your unit size, your risk of ruin as a percentage, and a chart of how your bankroll plays out across thousands of simulated runs. The rule of thumb is simple: if your risk of ruin is above 5%, reduce your unit size or take a hard look at your win rate, because it's probably unrealistic. The green zone is below 1-2%.
Why bankroll management matters
The main reason is surviving variance. Even a winning strategy goes through long losing stretches. That's mathematics, not bad luck. Bankroll management makes sure you're still in the game when your edge eventually shows up, rather than having blown everything during the first rough patch while running on emotion.
A fair warning: bankroll management does not turn a losing strategy into a winning one. If you have no edge over the bookmaker or the casino, the right unit size will only slow the bleed, it won't stop it. Managing your bankroll is about survival and controlling variance, not conjuring profits from thin air.
Different games call for different bankroll sizes. Sports bettors typically keep stakes at 1-2% per bet. Blackjack, even with basic strategy, demands a larger bankroll due to high variance. In poker, the standard measure is buy-ins: 50-100 buy-ins for cash games. On ToolsGambling, the calculator handles all of these scenarios and runs entirely in your browser, so your numbers never leave your device. If you want to dig deeper, there's also a Kelly calculator, a risk of ruin calculator, and a bankroll growth calculator below.
There's a psychological side to this too. Strict bankroll management is your best defence against tilt. When your unit is fixed and small, you don't chase losses by doubling up after a bad run and you don't throw half your bankroll at a "can't lose" bet on impulse. The number the calculator puts on your screen takes emotion out of the stake-sizing decision, and emotion is what empties bankrolls faster than anything else.
How the math works
Six steps the calculator runs every keystroke. Open methodology, no black box.
Read your bankroll
Disposable money only. The calculator never tracks deposits — what you enter is what it uses.
Pick a sizing method
Flat, Kelly full, fractional Kelly, units, or custom percentage. Each maps to a recommended unit.
Estimate edge and variance
Edge is your long-run advantage. Variance is how wild the swings get. Both feed the ruin formula.
Set the session horizon
How many bets, hands, or sessions you plan to play. Horizon and unit together determine ruin.
Read the live readout
Unit, ruin, drawdown, ROI, sessions-to-double — all update in real time. No submit button.
Stress-test with Monte Carlo
100 randomized paths show the realistic distribution. Save the plan, share the URL.
The math behind it (transparency)
Every number on this page is computed in your browser using public bankroll formulas. Nothing leaves your device. The three formulas below are the load-bearing ones.
Kelly fraction
f* = edge / (odds − 1) for sports. For symmetric bets f* = 2p − 1, where p is win probability. Fractional Kelly multiplies f* by 0.25–0.75 to soften variance.
Risk of ruin
RoR ≈ ((1 − edge·unit/sigma²) / (1 + edge·unit/sigma²))^(bankroll/unit). Larger unit, lower edge, or higher variance all push ruin up.
Monte Carlo trajectory
Each session draws a random outcome from a distribution calibrated to your variance preset. We run 100 paths so you see realistic best/worst cases, not just averages.
Choosing between flat, Kelly, and fractional
There is no universally correct sizing method. The right choice depends on three honest answers.
- 1Do you actually know your edge? Flat staking is safer when edge is fuzzy or estimated.
- 2How much variance can you stomach? Full Kelly is mathematically optimal but feels brutal in a downswing.
- 3Are you playing many small bets or few big ones? Many small bets favour fractional Kelly; few big ones favour flat.
- 4Are you withdrawing or compounding? Compounding pairs naturally with Kelly; withdrawing pairs better with flat units.
- 5Is the bankroll discretionary? Bigger ruin tolerance = more aggressive sizing is acceptable.
- 6Have you logged at least 1,000 results at this game? If not, prefer half-Kelly or smaller until variance is real.
When bankroll math fails: the variance trap
Two ways even a perfect plan blows up.
Edge that exists only on paper
If your +2% edge is really +0.2%, your unit is 10× too large. Most bettors over-estimate edge by a factor of 3–5×. Cut everything in half until you have 1,000+ logged results.
Variance you have not actually felt
Reading 'high variance' is not the same as living a 40-buy-in downswing. Until you have survived a real downswing in this game, prefer fractional Kelly or flat units.
Mini glossary
Ten terms that matter, defined in one sentence.
Five common mistakes
What kills bankrolls in practice.
- 01Sizing off total wealth instead of dedicated bankroll
- 02Using full Kelly on an estimated edge
- 03Ignoring variance after a winning streak (winner's tilt)
- 04Increasing unit after losses to recover faster
- 05Counting each-way and parlays as flat single bets
Bankroll Calculator FAQ
Advanced tools
Specialist calculators for specific bankroll questions.
Bankroll Growth Calculator
Project compound growth, ROI curves, drawdown — long-form planner.
Kelly Criterion Calculator
Pure Kelly fraction, full or fractional, with ROI projections.
Risk of Ruin Calculator
Standalone ruin probability with adjustable confidence.
Staking Plan Calculator
Compare 6 staking systems including level stakes, percentage, and progressive.
Casino Session Bankroll
Single-session sizing for slots and tables, RTP-aware.
Poker Bankroll Tracker
Cash and tournament buy-in management with risk profiles.
Related guides
Live cluster — explore the 13 supporting reads.
Bankroll Management: Complete Guide
Foundation read covering stakes, risk, and survival.
Kelly Criterion Explained
Full vs fractional Kelly with sport-specific examples.
Risk of Ruin: Survival Guide
What ruin probability means and how to lower it.
What Is Bankroll Management
Beginner's guide to managing betting capital.
How to Calculate Bankroll Units
Four methods to size your unit correctly.
Bankroll for Sports Betting
Sport-specific stake sizing and survival rules.
What % of Bankroll to Bet
Why 1-2% wins long-term over chasing bigger bets.
Kelly vs Flat Staking
Which staking method actually wins? Side-by-side test.
How Risk of Ruin Works
Bankroll survival math without the heavy formulas.
Bankroll for Blackjack
Stake-by-stake survival framework for table play.
Bankroll for Poker
Cash and tournament buy-in math for grinders.
Video Poker Bankroll Strategy
Max-coin variance and the bankroll it really needs.
Bankroll Growth vs Flat Staking
Why compounding beats flat — and when it doesn't.
Evgeniy Volkov
Verified ExpertFullstack developer with a background in mathematics. I build the calculators and game-style tools on ToolsGambling with Pixi.js and modern web tech, and every result uses transparent probability formulas you can verify yourself.