What is a two-book lock (arbitrage)?

When two sportsbooks price opposite sides of the same line generously enough, betting both sides in the right amounts guarantees a profit no matter the result. The Lock Checker tells you the exact stake for each book and the guaranteed return per $100, vig included.

What are no-vig (fair) odds?

Sportsbooks build a margin (the vig) into every price. Removing it reveals the market's true probability for each side — the number to beat before a bet has positive expected value.

How does the Kelly criterion size a bet?

Kelly computes the bankroll fraction that maximizes long-term growth from your edge: (probability × decimal odds − 1) ÷ (decimal odds − 1). Most bettors stake a half or quarter Kelly to reduce variance.

🧪 The Bet Lab · every number, vig included

Eight instruments. Zero guesswork.

The math the books use, turned around and pointed back at them — lock detection, fair prices, stake sizing and edge measurement. Works for every league, every season, every book.

⚾ MLB🏀 NBA🏈 NFL🏒 NHLANY BOOK

🟢 GUARANTEED-PROFIT SCANNER — LIVE

FantasyDailies hunts risk-free two-book locks across 9+ sportsbooks, all day. Exact stakes, profit per $100, vig included.

Open the Middle Finder →

🟢 LOCK CHECKER — can these two prices guarantee money?VIG INC.

Side A price (American)

Side B price (American)

Book A (optional)

Book B (optional)

Total to stake

Opposite sides of the same line, two different books.

Enter both prices.

Plus-money on both sides is where locks live — the Middle Finder hunts them automatically.

Odds Converter3-way live

American

Decimal

Implied %

Type in any box — the other two follow. Implied % includes the book's vig.

No-Vig Fair Pricetwo-way

Side A price

Side B price

Fair A / Fair B—

Book hold—

Fair prices are what the market believes with the margin stripped out — the line your bet has to beat.

Expected Valueper $100

Your win %

Price offered

EV per $100—

If your probability is right, this is your long-run profit or loss per $100 staked.

Kelly Stakegrowth-optimal

Bankroll $

Win %

Price

Kelly fraction

Stake—

Kelly only bets when you have an edge — no edge, no bet.

Break-Even %the bar to clear

Price (American)

Win % needed—

Win more often than this and the bet prints long-term. Win less and it bleeds.

Quick Parlayup to 5 legs

Leg 1

Leg 2

Combined—

$100 pays—

Full builder with live legs: the Parlay room →

ROIrecord → return

Bets won

Bets lost

Avg price

ROI—

Flat $100 stakes assumed. A winning record can still lose money at bad prices.

Hedge Calculatorits own room

Already holding a ticket that's live to cash? The hedge room sizes the exit — lock a profit or cap the loss.

Open the Hedge Calculator →