How to use this tool

A quick guide to running a slippage check on a prediction market.

1. Find a market

Open any market on polymarket.com or kalshi.com and copy its URL from your browser's address bar. For Kalshi you can also paste a ticker like KXHIGHNY-26MAY05.

2. Paste the URL

Drop the URL into the Market URL field on the home page.

3. Enter your budget

Put the dollar amount you'd hypothetically spend into the Budget (USD) field. The tool walks the live order book and calculates what you'd actually pay — including slippage — instead of just showing the top-of-book price.

4. (Optional) Set a slippage threshold

If you fill in Threshold (%), the tool will also report the maximum budget you could spend before slippage exceeds that percentage versus the reference price. Leave it blank to skip.

5. Read the results

Best bid / ask / mid — the current top of the order book.
Avg price — what your shares would actually cost on average if you swept the book with your budget.
Slippage vs touch / mid — how much worse your average fill is compared to the best ask and the mid price.
Filled — whether the book had enough depth to absorb your full budget.

Tip: try the same budget on two different markets to compare liquidity. Thin markets blow up slippage fast — that's the whole point of checking before you click buy.