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How to Read a Polymarket Order Book

Guide with a live order book · updated October 6, 2026

An order book lists every resting order to buy (bids) and sell (asks) an outcome. On October 6, 2026 the book for No change in “Fed Decision in October?” showed a best bid of 81.0¢ (48,705 shares) and a best ask of 82.0¢ (287,614 shares): a 1.0¢ spread around a 81.5¢ midpoint — the number Polymarket shows as the probability.

Live example: Fed Decision in October? — No change

Bids (buyers)

Price	Shares	Cumulative $
81.0¢	48,705	$39,451
80.0¢	145,872	$156,149
79.0¢	105,420	$239,431
78.0¢	79,673	$301,577
77.0¢	14,170	$312,488
76.0¢	31,845	$336,690
75.0¢	11,679	$345,449
74.0¢	276,630	$550,155

Asks (sellers)

Price	Shares	Cumulative $
82.0¢	287,614	$235,844
83.0¢	161,252	$369,683
84.0¢	15,063	$382,336
85.0¢	17,357	$397,089
86.0¢	5,419	$401,749
87.0¢	8,256	$408,932
88.0¢	13,113	$420,471
89.0¢	20,995	$439,157

Tick size 0.01 · minimum order 5 shares · last trade 81.0¢ · snapshot October 6, 2026, refreshed twice a day.

What a market buy would cost right now

Spend	Shares	Average price	vs best ask
$100	122	82.00¢	+0.00¢
$1,000	1,220	82.00¢	+0.00¢
$10,000	12,195	82.00¢	+0.00¢
$50,000	60,976	82.00¢	+0.00¢

Walks the asks from the cheapest up; fees not included (see Polymarket fees). With fees and your own order size: spread and slippage calculator.

How to read it

📗 Bids are buy orders: the highest bid is what you get if you sell right now.
📕 Asks are sell orders: the lowest ask is what you pay if you buy right now.
↔️ Spread = best ask − best bid. A 1¢ spread is tight; wide spreads mean you give up more to trade instantly.
🎯 Midpoint = halfway between best bid and best ask — the probability shown on Polymarket. If the spread is wider than 10¢, Polymarket shows the last trade instead (Polymarket Help Center).
📚 Depth = how many shares sit at each price. Thin depth means a large order moves the price (slippage).
🧾 Maker vs taker. A limit order that rests on the book is a maker order (no fee); an order that fills against the book pays the taker fee.

Why a YES bid is also a NO ask

Every market has two outcome shares that together pay $1. Buying YES at 68¢ is economically the same as selling NO at 32¢, so the YES and NO books mirror each other: a bid for YES at p appears as an ask for NO at 1 − p.

Try it on live markets

Put real prices into the calculator: every page below shows current odds, 24-hour moves and the market rules.

Bitcoin odds · Fed rates odds · Politics odds

Most traded right now:

Next French Presidential Election Marine Le Pen 43%
UEFA Champions League: 2027 Champion Barcelona 22%
Bitcoin above ___ on October 6? 80,000 100%
Presidential Election Winner 2028 JD Vance 20%
Next Prime Minister of Spain? Alberto Núñez Feijóo 82%

Frequently asked questions

What is the spread on Polymarket?

The gap between the best ask (lowest sell price) and the best bid (highest buy price). Liquid markets often trade with a 1¢ spread; thin markets can be several cents wide.

Why does the Polymarket price differ from what I pay?

The displayed probability is the midpoint of the spread (or the last trade when the spread is wide). A market buy pays the ask — and more if your order is larger than the shares offered at the best price — plus any taker fee.

How do I avoid slippage on Polymarket?

Use limit orders at the price you want, split large orders, and check the depth first: the table above shows what spending $100 to $50,000 would cost right now.

🔔 Free Telegram watchlist of big odds moves

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