The Mark Price

Every trade on PredMart — opening, closing, or liquidation — uses the Mark price: a fair, manipulation-resistant price taken from Polymarket's live order book.

How the Mark is calculated

The Mark is the average price to sell $1,000 of shares into Polymarket's order book right now — a "$1,000 depth walk." Instead of trusting a single quote at the top of the book (which anyone could fake), PredMart walks down the real orders until $1,000 of volume is covered and takes the average, weighted by the size behind each price.

That is what makes the Mark hard to cheat:

• A single fake order at an extreme price barely moves a $1,000 average.
• To move the Mark, someone would have to commit real money across many price levels — more than they could ever gain from it.

You can check it yourself

The Mark is built entirely from Polymarket's public order book (its CLOB) — the same live data anyone can see. You can pull Polymarket's order book and run the same $1,000 depth walk to confirm the price PredMart used was fair. Nothing is hidden or invented.

Related Pages

• Margin and Liquidation — how the Mark determines when a position is liquidated.
• Fees — entry, profit, and holding fees applied at open and close.