MoneyKey number

Expected value: what a bet is worth on average

Expected value, or EV, is what a bet returns on average if you could make it many times. EV = chance to win × profit − chance to lose × stake. A positive number means the price is better than your true chance.

Reviewed Oct 15, 2026

Answer first

90s

01EV compares the price with the real chance.
02A -110 bet needs 52.4% to break even.
03Most bets have negative EV because of vig.

Key numbers

EV in numbers

52.4%Break-evenAt -110

40%Break-evenAt +150

+$12.50EV per $100+150 at 45%

-$4.55EV per $110-110 at 50%

In short

Key takeaways

EV is an average over many bets, not one result.
Price shopping raises EV.
A good team can still be a bad bet at the wrong price.
Track results to check your estimates.

Progress

Working out EV

1
Your chance
p
2
Profit if win
From the odds
3
Stake if lose
What you risk
4
EV
p × profit − (1 − p) × stake

Use the same stake in every step.

Break-even by price

American odds	Profit per $100	Break-even chance
-200	$50	66.7%
-110	$90.91	52.4%
+100	$100	50.0%
+150	$150	40.0%
+300	$300	25.0%

Break-even equals implied probability.

Two worked examples

You bet $100 at +150 on a team you think wins 45% of the time. EV is 0.45 × $150 minus 0.55 × $100, which is $67.50 minus $55, or +$12.50. Over many such bets you expect to gain about 12.5 cents per dollar.

You bet $110 to win $100 at -110 on a true coin flip. EV is 0.5 × $100 minus 0.5 × $110, or −$5. Per $110 risked that is about −4.55%. That is the vig at work.

The same team at a different price can flip from negative to positive EV. That is why bettors compare prices at several licensed books.

EV of a $100 bet at +150

Your chance	Win part	Loss part	EV
35%	$52.50	−$65	−$12.50
40%	$60	−$60	$0
45%	$67.50	−$55	+$12.50
50%	$75	−$50	+$25

Our own sums.

Why most bets are negative EV

Books add vig to both sides. In a -110 / -110 market, the implied chances add to 104.8%, not 100%. The extra 4.8% is the book’s margin. To beat it, you need a better estimate than the market.

Parlays and props often carry higher margins, so their EV is usually worse. Boosts and promotions can push EV above zero for a single bet, which is why sharp bettors read the terms closely.

A no-vig price helps here. Take both sides of a market, convert each to a chance and scale them so they add to 100%. That fair chance is a starting point for judging any price you see at another book.

Sequence

Checking a bet’s EV

Step 01
Estimate the chance
Use data or a model.
Step 02
Convert the price
Find break-even.
Step 03
Compare
Your chance vs break-even.
Step 04
Work out EV
Per $100 staked.
Step 05
Record it
Check over many bets.

EV and variance

A positive EV bet can lose many times in a row. A +150 bet at 45% loses 55% of the time. Over 20 such bets, losing 13 or more happens often. EV is about the long run, not the next ticket.

That is why EV pairs with bankroll rules. Small, steady bet sizes let a real edge show itself.

A simple record helps. Write down the price, your estimated chance and the result for every bet. After a few hundred bets, compare your average estimated EV with your actual profit. A large gap means your chances need work.

Floor rules

EV terms

Know before you sit

EV: Average result of a bet over many tries.
Break-even: Chance needed for EV of zero.
Vig: The book’s margin.
Positive EV: A price better than the true chance.

Common mistakes

Judging by one result: EV is about many bets.
Ignoring vig: It lowers every EV.
Overrating your picks: Use records, not feelings.
Skipping price shopping: Better prices raise EV.

Keep reading

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After the 90 seconds

Questions before and after you play

A 90-second guide cannot cover every table moment. Tap a group, then a question — answers are short paragraphs, not one-liners.

01Basics

What is expected value in betting?

The average profit or loss of a bet if made many times: chance to win times profit, minus chance to lose times stake.

What is a positive EV bet?

One where the price pays more than your true chance deserves. Over many bets, it should make money.

What does break-even mean?

The win rate where EV is zero. At -110 it is 52.4%. Rules differ between licensed sportsbooks, so read the house rules.

02Math

How do I find break-even for plus odds?

Divide 100 by the odds plus 100. At +150, 100 ÷ 250 is 40%. Rules differ between licensed sportsbooks, so read the house rules.

How do I find break-even for minus odds?

Divide the odds by the odds plus 100. At -110, 110 ÷ 210 is 52.4%. Rules differ between licensed sportsbooks, so read the house rules.

Why do two -110 sides add to more than 100%?

Each implies 52.4%, together 104.8%. The extra is the vig. Rules differ between licensed sportsbooks, so read the house rules.

03Practice

Can I lose with positive EV bets?

Yes, often in the short run. EV only shows over many bets. Rules differ between licensed sportsbooks, so read the house rules.

Do boosts make bets positive EV?

Sometimes. A big boost on a fair price can give positive EV, but check the stake limits.

How do I know my estimate is good?

Track many bets and compare with the closing line. Beating it often is a good sign.

Sources

Wikipedia — Expected value Not from a registry (Reference source, not an official registry) · accessed Oct 15, 2026Definition and examples
Wizard of Odds — Sports betting Not from a registry (Reference source, not an official registry) · accessed Oct 15, 2026Sports betting math
American Gaming Association — Sports betting Not from a registry (Reference source, not an official registry) · accessed Oct 15, 2026US legal sports betting data
National Council on Problem Gambling — Help and resources Not from a registry (Reference source, not an official registry) · accessed Oct 15, 2026Free, confidential help: call or text 1-800-GAMBLER