OSOTOTO — the sharp bettor’s calculator toolkit
21 fast, private calculators for betting and casino math — odds, expected value, Kelly staking, arbitrage, house edge and more. Everything runs in your browser.
Explore calculators Read the guidesBetting calculators
Odds Converter
Convert decimal, fractional, American, Hong Kong & implied probability instantly.
Expected Value (EV)
Find the true EV, edge and ROI of a single bet.
Vig Remover / True Odds
Strip the bookmaker margin to reveal fair odds and true probability.
Parlay / Accumulator
Combine up to 20 legs into one payout with combined odds.
System Bet (Lucky 15/31/63)
Trixie, Yankee, Lucky 15/31/63 — full breakdown of combination bets.
Each-Way Calculator
Split win/place, apply place terms and see total return.
Closing Line Value (CLV)
Measure how much better your odds were than the closing line.
Advantage play calculators
Arbitrage (Surebet)
Guaranteed-profit staking across 2 or 3 bookmakers.
Dutching
Back multiple selections for equal profit whichever wins.
Matched Betting
Qualifying loss and free-bet profit with back/lay & exchange commission.
Hedge / Cash-Out
Lock in profit or cut losses by hedging the opposite side.
Back/Lay (Exchange)
Lay stake and liability for a betting-exchange position.
Bankroll & risk calculators
Kelly Criterion
Optimal stake size from your edge — full, half & quarter Kelly.
Risk of Ruin / Drawdown
Probability of losing your bankroll given edge, odds and bet size.
Session Budget
How long a bankroll lasts at a given bet size and pace.
Staking Plans Simulator
Simulate Martingale, Fibonacci, D’Alembert, flat — with a bankroll chart.
Casino & slots calculators
House Edge → Cost/Hour
Turn RTP and pace into an expected hourly cost.
Slot Variance Simulator
Monte-Carlo a slot session and see the outcome distribution.
Bonus Wagering
Total turnover, expected cost and EV of a casino bonus.
Roulette Odds
Payouts and true probabilities for every roulette bet (EU/US).
Poker Odds (Pot Odds & Outs)
Pot odds, outs-to-equity and call/fold guidance.
Learn & track
Guides
Plain-English explainers on bankroll, RTP, value betting and reading odds.
Glossary
18 betting & casino terms defined clearly.
Bet Tracker
Log bets, see ROI, strike rate and a P/L chart — stored only on your device.
OSOTOTO is an independent, free educational tool. We do not take bets or offer gambling. Please gamble responsibly — take the self-check or visit responsible gambling resources. 18+.
Frequently asked questions
Does OSOTOTO accept bets?
No. OSOTOTO is a free educational calculator site. It does not accept wagers or offer gambling.
Do I need to sign up to use the calculators?
No. The calculators run in your browser and can be opened without registration.
Where does the bet tracker keep my entries?
The tracker keeps entries on your device in the browser. It is separate from the calculators and is not a betting account.
