Free Virtual Sportsbook
Simulated matches between invented teams, a bet slip, and play chips that are worth nothing, with the bookmaker's margin on show before you place anything.
Play chips
1,000
No real money, no prizes, nothing to buy.
Simulated slate
Invented teams. American odds, decimal beneath.
- Match 1
- Match 2
- Match 3
- Match 4
- Match 5
- Match 6
Tap a price to add it to your slip.
Bet slip
Nothing on the slip yet. Each price you tap is added with the chip you have selected.
Session coach
Last round
Nothing played yet. After each of your slips the coach says what the round cost and what decided it.
Decide the cost before you start
Gambling is entertainment with a price, like a concert ticket. The useful question is not how much you might win but how much the evening is allowed to cost. Pick that number first, and treat reaching it as the end of the session. You can set one below and the coach will hold you to it.
Next bet
No bet lined up. Once there is one, its expected cost shows here before you play it.
- Slips played
- 0
- Chips bet in total
- 0
- Bets raised after a loss
- 0
Where the result came from
- House edge, on average
- 0
- Luck
- 0
- Result
- 0
The report fills in as you play. Take the margin out of any market
Set a session limit
This table is for practice and entertainment only. How to keep gambling safe
What this slip costs
- Chips on the slip
- 0
- Expected cost
- 0
- 4.5% of any stake
Every price on this board is set about 4.5% short of fair. That margin is the price of the bet, whichever side you take. Add a selection to see what its price claims. Take the margin out of any market
This session
- Slips
- 0
- Chips staked
- 0
- Net chips
- 0
- Expected at these prices
- 0
Expected is the margin on each slip you placed, measured against the true chances and taken on the chips you staked. A short session swings well away from it in both directions.
Built by Alexander Korsager · last updated October 3, 2026 · corrections
- The bookmaker's margin on every stake at this board
- 4.5%
- Posted on both sides of an even match
- −110
- Margin on a 3-leg parlay at these prices
- 12.9%
- Margin on a parlay of all 6 matches
- 24.1%
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A board that shows what the margin costs
A sportsbook does not charge a fee. It builds its price into the odds: every side of every match pays a little less than its true chance deserves, and that shortfall is the margin.
On this board it is 4.5% of every stake, so an even match is posted at −110 (1.91) on both sides, a price that claims a 52.4% chance for a side that has 50%. The margin is the price of every bet, on the favorite and the underdog alike.
- Either side of an even match−1101.91
- True chance
- 50%
- The price claims
- 52.4%
- Kept from each stake
- 4.5%
- A clear favorite−2751.36
- True chance
- 70%
- The price claims
- 73.3%
- Kept from each stake
- 4.5%
- The underdog in that match+2183.18
- True chance
- 30%
- The price claims
- 31.4%
- Kept from each stake
- 4.6%
A price breaks even only at the chance it claims. The gap to the true chance is the margin, and it is about the same on every side of this board.
A parlay pays that price once per leg.
Each leg's whole return rides on the next, so the margins multiply: 12.9% of the stake on a 3-leg parlay at these prices, and 24.1% on all 6 matches. The panel under the table works this out for the slip as you build it, from the posted prices alone. Once the slate is played the true chances are revealed, so you can check what each price was really worth. That comparison is what is worth practicing here.
- A single4.5%
- 2-leg parlay8.8%
- 3-leg parlay12.9%
- 4-leg parlay16.8%
- 5-leg parlay20.6%
- 6-leg parlay24.1%
The average share of the stake kept, with every leg at this board's margin and the legs unrelated.
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Rules at this table
Singles
- Selections
- Each one is its own bet
- Stake
- One per selection
- Pays
- Stake times the decimal price
- Paid when
- Its side wins
Margin on each bet
4.5%
Each bet is priced on its own.
Parlay
- Selections
- 2 or more, as one bet
- Stake
- One for the whole slip
- Pays
- Stake times every leg's decimal price multiplied together
- Paid when
- Every leg wins
Margin on the bet
8.8% to 24.1%
From 2 legs up to all 6 matches, at these prices.
- Each slate is 6 simulated matches between invented teams. Every match has two sides and one of them wins: there are no draws.
- Prices are shown as American odds with the decimal equivalent beneath. A positive number is the profit on 100 staked. A negative number is the stake needed to make a profit of 100.
- Tap a price to add that side to the slip. A slip holds one side per match.
- Any one bet takes up to 500 chips. Placing the slip plays every match on the slate, and the true chances are shown once the last result is in.
The teams and matches are generated in your browser. They are not real teams, and no result here follows or predicts any real event.
FAQ
- Is this sportsbook played for real money?
- No. The table uses play chips that have no value, cannot be bought, and cannot be cashed out or exchanged for anything. If you run out, you are handed another stack for free. There is no account and nothing to download.
- What is the bookmaker's margin?
- It is the gap between what a price pays and what the true chance would pay. A side with a 50% chance is fair at +100 (2.00). This board posts it at −110 (1.91), and the difference costs 4.5% of every chip staked on it, on average. Add up what the two posted prices claim and the total comes to more than 100%: the excess is the same margin seen from the other side.
- Why does a parlay cost more than a single bet?
- Because every leg carries its own margin and a parlay rolls the full return of one leg into the next. A single at this board's margin returns 95.5% of the stake on average. Two legs return that share of that share, and so on, so a 3-leg parlay costs 12.9% of the stake and a 6-leg parlay 24.1%. The payout grows with each leg only because the chance of every leg landing shrinks faster.
- Is the favorite the safer bet?
- It wins more often, and it is priced for that. A favorite with a true 70% chance is posted here at −275 (1.36) against a fair −233 (1.43), and the underdog in the same match at +218 (3.18) against a fair +233 (3.33). Both cost about the same share of the stake. A price only favors the bettor when it pays more than the true chance deserves, and no price on this board does.
How this game works
Each match is given a favorite whose true chance of winning is a whole percent from 50 to 80, on a side picked at random. The posted price is the fair price for that chance with 4.5% taken out of the payout, rounded to whole American odds the way a book quotes them. The conversions use the same module as the betting odds converter. Because of the rounding, the margin on an individual price sits a fraction of a point either side of 4.5%.
Before the slate is played, the panel estimates each fair chance by dividing what a price claims by the total both sides claim, the proportional method from the no-vig fair odds calculator. A selection's margin is its expected loss per chip at that fair chance, and a parlay's margin is 1 minus the product of each leg's share kept, which is the same figure the parlay payout calculator reaches from the combined price. After the slate is played the same sums are shown at the true chances.
Each result is one random number drawn in your browser against the home side's true chance. Nothing depends on your slip, your balance or earlier slates. The first slate is the same for every visitor, and every slate after it is drawn fresh.
Limits
- Real sportsbooks set different margins on different sports and markets, and often take more from long shots than from favorites. This board charges every side about the same.
- The fair chance shown before a slate is an estimate from the posted prices. A real bettor never gets to see the true chance afterwards, which is what makes a margin hard to notice.
- A parlay's margin compounds this cleanly only when its legs are unrelated, as these matches are. Related legs are priced differently by real books.
- Play chips do not feel like money. A losing run that is easy to sit through here is harder with a real stake.
This is a practice game for adults. It has no real-money play and links to none. Sports betting for money carries the bookmaker's margin on every bet, and no amount of practice on simulated matches removes it.
Gambling can cause serious harm. The National Problem Gambling Helpline is free, confidential and open 24/7, call or text 1-800-MY-RESET (1-800-697-3738), or chat at ncpgambling.org/chat.
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