A prediction market is a market where a contract's price is a direct stand-in for a probability. You're not picking a winner and waiting. You're buying or selling a claim on an outcome at a price that moves every time someone else trades. If you've never placed an order in one, the learning curve is short. The part that actually matters, reading the price correctly and sizing your risk, is what this guide covers.
What a prediction market contract is
Every market resolves to one of a small set of outcomes, often just YES or NO. A contract on that outcome settles at $1.00 if it happens and $0.00 if it doesn't. Nothing in between. Because the payout is fixed at $1 and $0, the price you pay today is automatically an implied probability.
That's the core idea to internalize before anything else: a 74¢ YES contract means the market is pricing that outcome at roughly 74%. Buy it at 74¢ and you're risking 74¢ to make 26¢ if it resolves YES, or losing the full 74¢ if it resolves NO. Every market page you'll ever look at, on Polymarket or Kalshi, is showing you that same relationship in different clothing.
Order books vs. AMMs, briefly
Prices don't set themselves. They come from a matching mechanism, and prediction market platforms use a couple of different ones.
- Central limit order book (CLOB). Buyers and sellers post limit orders at specific prices, and the exchange matches them. The best available buy and sell prices form the bid and the ask, and the gap between them is the spread. Kalshi runs on this model, and Polymarket's own order book has increasingly become the primary mechanism there too.
- Automated market maker (AMM). Instead of matching two traders directly, you trade against a liquidity pool that adjusts price algorithmically based on how much of each side has been bought. This is common on newer or thinner markets where a standing order book hasn't formed yet.
The practical difference for you as a trader is mostly about liquidity and spread. A deep order book gives you tighter spreads and more predictable fills. A thin market, order book or AMM, means your own order can move the price against you, which is called slippage. Check the spread and depth before sizing a trade, not after.
Reading a market page
Every market page is built from the same handful of components. Once you know what you're looking at, scanning a new market takes seconds.
- The question and resolution criteria. The exact wording of what has to happen, and who or what source determines the outcome. Read this fully. Vague resolution criteria is a real source of disputes.
- The current price for each side. Shown as cents (Polymarket) or as a probability percentage (Kalshi). This is your implied probability, live.
- The order book or depth chart. Shows how much size sits at each price on the bid and ask. Thin books next to the current price are a warning sign for slippage.
- Volume and open interest. Rough proxies for how much capital and attention a market has, and therefore how reliable its price is likely to be.
- Price history. A chart of how the implied probability has moved since the market opened, useful for seeing what news moved the price and when.
Entry and exit mechanics
Getting into a position is placing a buy order on the side you think is underpriced, YES or NO, at either the current market price or a limit price you set. Getting out is the same motion in reverse: you sell your contracts back into the market at whatever the current price is.
This is the part that separates a prediction market from a fixed bet: you are not locked in until resolution. If a contract you bought at 50¢ trades up to 75¢ before the event happens, you can sell and take the 25¢ gain right now. If your read turns out wrong and the price drops, you can sell for whatever it's worth instead of riding it to zero. Managing a position (sizing in, taking partial profit, cutting a loser early) works the same way it does in any other tradeable market.
Common beginner mistakes
Most new traders don't lose money from bad predictions. They lose it from bad structure: the price they paid, the size they took, or the friction they ignored.
- Buying dead-certs at 98¢. A contract at 98¢ is priced at ~98% probability. Your maximum gain is 2¢; your maximum loss is 98¢. Even if you're right most of the time, one miss wipes out dozens of wins, and the spread and fees you pay to get in and out eat directly into that thin 2¢ edge. Being "probably right" isn't the same as the trade having good risk-reward.
- Ignoring fees and spread. Every entry and exit crosses a spread, and some platforms charge a trading fee on top. On a small edge, that friction can be the difference between a profitable strategy and a losing one. Always ask what a trade costs to get into and out of, not just what it might pay out.
- Position sizing off feel instead of a rule. Putting a large share of your capital on a single market because you're "confident" is how one wrong call erases a month of good ones. Size positions as a small, consistent fraction of your capital so no single market can knock you out.
- Treating price as certainty. A 74¢ price means 74% likely, not "basically guaranteed." Markets are frequently right, but the whole point of trading them is that they're not always right, and your edge only exists in the gap between the price and the real probability.
Polymarket vs. Kalshi: the factual differences
Both platforms let you trade event contracts where price equals implied probability, but they're built differently.
| Kalshi | Polymarket | |
|---|---|---|
| Structure | CFTC-regulated exchange | Global crypto-native platform |
| Settlement currency | US dollars | USDC |
| Matching | Central limit order book | Order book, with AMM liquidity on some markets |
| Market catalog | Economic data, politics, weather, and more, under exchange listing rules | Broad catalog including politics, crypto, sports, and culture |
| Price display | Implied probability / cents | Cents (implied probability) |
Neither fact set makes one platform inherently better to trade. They're different market structures with different rules, and traders often watch both for the same underlying question when it's listed on each. What matters for your edge is the same on both: how good your probability estimate is relative to the posted price, and how disciplined your entries, exits, and sizing are.
Trading with real size
Most beginners start with a small amount of personal capital, which caps what even a strong, repeatable edge is worth in dollar terms. Before risking anything, it's worth practicing the mechanics above (reading a market, watching how price reacts to news, entering and exiting) on a free $25K practice terminal, no funding required.
Once you can show a repeatable edge, a funded account is the path to trading it with real size instead of scaling a small personal account one trade at a time. A prediction market prop firm gives a trader who passes an evaluation access to a funded account and splits the resulting profit with them.
Frequently asked questions
What does a prediction market price actually mean?
The price is the market's implied probability. A YES contract trading at 74¢ means the market is pricing that outcome at roughly 74%. Contracts settle at $1 if the outcome happens and $0 if it doesn't, so price and probability move together by definition.
What's the difference between Polymarket and Kalshi?
Kalshi is a CFTC-regulated exchange offering event contracts to US users through a traditional central-limit order book. Polymarket is a global crypto-native platform that settles trades in USDC and has historically used a hybrid order book with AMM-style liquidity on many markets. Both display prices as implied probabilities and let you trade in and out before an event resolves.
Why do beginners lose money buying contracts at 98 cents?
A 98¢ contract is priced at roughly 98% probability, so the most you can make is 2¢ if you're right, but you can lose the full 98¢ if the near-certain outcome doesn't happen. The reward-to-risk ratio is inverted, and spread plus fees eat further into that thin 2¢ margin.
Can I exit a prediction market position before the event ends?
Yes. Both Polymarket and Kalshi let you sell a position at the current market price any time before resolution, so you can lock in a gain, cut a loss, or free up capital without waiting for the event to settle.
How do I start trading prediction markets with real size?
Most new traders start with small personal capital, which limits what a real edge is worth. A funded account gives a trader who can demonstrate a repeatable edge on a challenge access to real trading size, with the trader keeping 90% of the profit split.
Practice first. Then trade it funded.
Try the mechanics on a free $25K practice terminal, then pass one challenge to trade up to $100K in prediction markets, keeping 90% of profits, with no daily drawdown and no lifetime cap.
Start your challenge →