Here is the execution mistake I see most often: a trader has a decent market thesis, sees a thin book, uses a market order anyway, and gives up several cents per contract before the event even starts. That is real edge lost at entry. Understanding Kalshi liquidity is just as important as having a correct thesis.
If you came from equities or futures, you're used to deep books where you can move size without thinking twice. Prediction markets aren't there yet. Kalshi is the only CFTC-regulated prediction market exchange in the US, which means it's where serious domestic money has to go. But "serious" is relative. We're still in the early innings.
Liquidity on Kalshi varies dramatically by market type:
The bid-ask spread tells you a lot. On a hot Fed contract the day of an announcement, you might see spreads of one or two cents. On a "will X happen by December 2026" contract with minimal interest, you could be looking at fifteen to twenty cent spreads. That's the cost of doing business in thin markets.
Execution check: before I cross a spread in a thin book, I compare the price I wanted with the average fill I am likely to get. The Kalshi slippage calculator is the quick version of that math.
Here's the math that finally made me religious about execution. Say you're buying Yes contracts at 52 cents, expecting them to settle at 100. Your expected profit is 48 cents per contract. If slippage costs you 4 cents on entry, you just gave up 8% of your potential profit before the event even happens. Do that consistently and you're grinding away your edge.
Slippage compounds in prediction markets because:
I've watched traders with genuinely good reads on political outcomes still lose money because they executed poorly. The thesis was right. The trade was wrong.
After burning money on bad fills, I developed some habits that actually work.
This sounds obvious, but I still see people asking in the Telegram channel I run why their fills were so bad. Market orders on Kalshi eat through the book fast. Always use limits. Set your price, wait, and accept that sometimes you won't get filled. That's fine. Missing a trade is better than entering a trade at a price that destroys your expected value.
If you want to put $10,000 into a contract that settles in three weeks, don't do it all at once. Split it into chunks. Put in $2,000 today, see how the book responds, add more tomorrow. This is especially true for medium-liquidity markets where your order might actually move the price.
Spend ten minutes watching how the order book moves before you trade. Is there a pattern? Does someone keep refreshing bids at a certain level? Are there obvious walls? This information is free and most people ignore it completely.
Kalshi liquidity is best during US market hours, roughly 9 AM to 5 PM Eastern. Fed announcement days and election nights see the most volume. If you're trying to move size, do it when the market is actually active. Trying to fill a big order at 2 AM on a Sunday is asking for trouble.
I spent my first year on Polymarket before the geofence pushed me off. The liquidity there is genuinely better on major political contracts, and I won't pretend otherwise. They have more international volume and fewer regulatory constraints.
But here's the tradeoff: Kalshi is regulated by the CFTC, which means your funds are held in segregated accounts, you're trading in actual USD, and there's legal recourse if something goes wrong. You go through KYC, which is annoying, but you also don't have to worry about a rug pull.
For US-based traders who want to stay compliant and not deal with crypto custody headaches, Kalshi is the only real option. The liquidity is growing. It's not where it needs to be yet, but every quarter seems better than the last. You can see the current order books at kalshi.com and judge for yourself.
Not all Kalshi markets are thin. Some have enough depth that you can move real money without sweating.
If you're new and want to trade with decent liquidity, stick to these categories until you understand how the thinner markets behave.
Open the specific market page on Kalshi and look at the order book, which shows current bids and asks at each price level. The depth chart visualizes how much volume sits at different prices. If you see a wide spread between the best bid and best ask, or very few contracts at each level, that's a thin market where slippage risk is higher. Check this before every trade.
Several factors contribute. Niche markets with low public interest attract fewer traders. Contracts with distant expiration dates tend to be thinner because people prefer trading closer to resolution. Odd hours (nights, weekends) see less activity since most US traders aren't active. New market categories also take time to develop liquidity as traders discover them.
It depends on the market and timing. On high-volume contracts like Fed decisions during peak hours, you can often place multi-thousand dollar orders with minimal impact. On thinner markets, large orders will move the price. Using limit orders, scaling into positions gradually, and trading during active hours all help reduce market impact when you're working with size.
Kalshi order books can include professional and active retail liquidity, but depth varies by contract and time of day. I treat visible bids, asks, spread, and size as the evidence. If the book is thin, I do not assume hidden liquidity will save the fill.
Not financial advice. I trade my own money and you can lose yours. Do your own research.