How to Calculate Optimal Bet Size: Kelly, Staking, and Real Risk for Bettors
1. Why Bet Size Matters: More Than Just “How Much?”
Choosing the right bet size isn’t just about “how much can I win?” It’s about not losing your entire bankroll, maximizing long-term profits, and surviving the inevitable downswings every real bettor faces.
- What happens if your bet size is too big?
- You can go broke, even if you have an edge.
- Emotional tilt, chasing losses, “all-in” disasters.
- Exposed to “ruin” (bust) risk, even with a good winrate.
- What if your bet size is too small?
- You waste your edge — your profits barely grow.
- You don’t take full advantage of your skill.
The Truth: Most “gurus” ignore real math. Real bet sizing is about probability, edge, and risk tolerance — not just “betting your gut” or “going all in when sure”.
2. What Is the Kelly Criterion? (Simple Explanation)
The Kelly Criterion is the most famous formula for calculating optimal bet size in gambling, investing, and trading. It tells you exactly what fraction of your bankroll to risk on a single bet, so you maximize your long-term growth — but also avoid going broke.
f* = (bp – q) / b f* = Fraction of bankroll to wager b = Decimal odds – 1 (e.g., odds 2.5 → b = 1.5) p = Probability of winning (your true edge, not bookmaker’s) q = Probability of losing (1 – p)
Example:
- Odds: 2.5 (implied win %: 40%)
- Your calculated win chance: 48%
- b = 1.5, p = 0.48, q = 0.52
- f* = (1.5 * 0.48 – 0.52) / 1.5 = (0.72 – 0.52) / 1.5 = 0.133
Result: Bet 13.3% of your bankroll.
But beware: If your edge is tiny or negative, Kelly will tell you to bet nothing or even “bet against” (short the market).
3. How to Calculate Bet Size: Step-by-Step
- Estimate your true win probability (not bookmaker’s line).
- Use your own data, stats, model, or real betting record.
- Find the odds (decimal, American, or fractional).
- Apply the Kelly formula (or use a bet sizing calculator).
- Adjust for risk tolerance:
- Full Kelly is aggressive (max growth, max variance).
- Fractional Kelly (e.g., 50% or 33%) is safer — most pros use 1/2 or 1/3 Kelly.
- Run simulations:
- Don’t trust just “theory” — see possible bankroll paths.
- A good bankroll simulator (like TrueBetVision) will show your true risk: bust % chance, average, worst-case scenarios.
Quick Example Using a Bet Sizing Calculator:
- Odds: 2.0 (evens)
- Win chance: 55%
- Kelly: (1 * 0.55 – 0.45) / 1 = 0.10 → Bet 10% of your bankroll
4. Other Popular Staking Plans
| Plan | Description | Pros | Cons |
|---|---|---|---|
| Flat betting | Always bet same amount (e.g., 1% bankroll) | Simple, easy | Ignores edge, slow growth |
| Fixed % | Bet fixed % of bankroll (e.g., always 2%) | Adapts to bankroll | Still ignores edge |
| Proportional | Bet more when edge is higher | Math-based | Needs good estimate |
| Martingale | Double after loss, “never lose” (danger!) | Looks easy | Ruins you! |
| Custom | Your own formula | Flexible | Needs math/discipline |
Warning: “All-in” and “chase loss” strategies bust bankrolls. Most “how to win fast” searches end in ruin!
5. Why Simulations Beat Guesswork
Real betting ≠ Theory! Even with a positive edge, downswings and “bad runs” happen — that’s why bankroll simulation is the new standard for pros.
- Why run 1,000–10,000 simulations?
- See the full range of possible outcomes (not just average).
- Find your chance of busting, doubling up, or achieving your goal.
- Understand “risk of ruin”, variance, and why discipline > luck.
- Answer real questions:
- “How much should I bet if I want to never go broke?”
- “Should I ever go all-in?”
- “How big should my bet be on Dota 2/CSGO?”
- How TrueBetVision Helps:
- Run up to 10,000 scenarios per session
- See median, 10% worst, and best-case results
- Supports esports, sports, crypto betting — any odds/edge
6. FAQ: All Your Bet Sizing Questions Answered
- How much should I bet?
→ Use Kelly, but reduce to half/third for safety. Never go all-in, even on “sure wins”. - Is it safe to bet my whole bankroll?
→ No. “All-in” is a fast track to bust, even if your model is perfect. - Can I use bet sizing calculators for esports (CSGO/Dota 2)?
→ Yes! Just enter your true winrate and odds — works for any game. - How do I avoid losing my bankroll?
→ Never bet above Kelly, always use simulations, keep discipline. - What if I’m not sure about my edge?
→ Be conservative. Underestimate your probability, or use half Kelly. - Why do most “safe staking systems” fail?
→ They ignore the real risk/variance. Simulate your plan to see the truth!
7. Try TrueBetVision Free
Ready to move from guesswork to real math? Try the TrueBetVision bet sizing calculator and bankroll simulator now.
No “info-guru” hype, just numbers.
See your real risk, not just “average ROI”.
Supports Kelly, optimal, custom staking — for Dota 2, CSGO, sports, crypto, and more.