About this guide: I'm Lawrence, the writer behind supa.is. Between February and May 2026 I've published 150+ articles on supa.is across crypto and brokerage tooling — including 40+ Hyperliquid-specific guides (recent examples: Hyperliquid Hypercore Order Book Explained (2026), Hyperliquid Order Not Filling? Slippage Fix (2026), Hyperliquid Maker vs Taker Fees: How Limit Orders Save You Money (2026 Guide)). The most-repeated reader question across that Hyperliquid archive is exactly how to turn visible order book depth into an expected fill price, which is why I'm publishing this standardized guide instead of answering one-off.
This guide is not another order book overview. It is a fill-price math guide. The goal is to answer one question before you click: if I send this size now, what average price should I expect?
On Hyperliquid, a market order is matched against resting limit orders, level by level. The first level gives you the spread cost. The remaining levels give you the slippage cost. If you only look at the last trade price, you are estimating from history. If you look at the book, you are estimating from available liquidity.
The three numbers that matter
You need three inputs:
- Best ask size for a buy, or best bid size for a sell.
- Size at the next few levels on the side you are crossing.
- Your order size.
A simple example:
| Ask level | Price | Size |
|---|---|---|
| 1 | 60,010 | 4 |
| 2 | 60,020 | 3 |
| 3 | 60,035 | 10 |
- 4 units at 60,010
- 3 units at 60,020
- 3 units at 60,035
(4 × 60,010) + (3 × 60,020) + (3 × 60,035) ÷ 10 = 60,020.5
The best ask was 60,010. Your estimated slippage is 10.5 points, or about 0.0175% on a 60,000 price level.
That is the whole calculation. Most bad fills happen because traders skip it.
Spread is the first cost, not the total cost
The spread is the gap between the best bid and the best ask. If the best bid is 60,000 and the best ask is 60,010, the spread is 10 points.
For a market buy, you cross that 10-point spread immediately. But the spread only tells you the first level. It does not tell you whether the first level has enough size.
A book can have a 10-point spread and still produce large slippage if the best ask size is small. A book can have a 50-point spread and produce low slippage if the best ask size is large enough to absorb your order.
This is why “the spread is tight” is not enough. You need the size behind the spread.
Depth is the second cost
Depth is the size resting at each price level. It determines how far your order walks the book.
If your order is smaller than the best level, your fill estimate is simple: you fill at the best ask (for a buy) or best bid (for a sell). Your slippage is just the spread.
If your order is larger than the best level, your fill estimate becomes a weighted average across multiple levels.
Example:
| Ask level | Price | Size |
|---|---|---|
| 1 | 60,010 | 12 |
Now compare:
| Ask level | Price | Size |
|---|---|---|
| 1 | 60,010 | 4 |
| 2 | 60,020 | 3 |
| 3 | 60,035 | 10 |
The difference is depth, not spread.
How to estimate your fill price in 30 seconds
Use this routine:
- Write down your order size.
- Read the best ask size for a buy, or best bid size for a sell.
- If your order is smaller than that size, your estimated fill price is the best ask or best bid.
- If your order is larger, subtract the best level size from your order size.
- Move to the next level and repeat until your order size is covered.
- Calculate the weighted average.
Average fill price = Σ (size at level × price at level) ÷ total order size
This is not a guarantee. The book changes. But it is a realistic expectation instead of a hopeful one.
If the estimated average fill price is too far from the last trade, the book is not deep enough for that order size at that moment.
Why limit orders change the math
A market order crosses the book. A limit order rests in the book.
A market order gives you fill certainty and price uncertainty. A limit order gives you price certainty and fill uncertainty.
Like what you're reading? Try it yourself — this link supports ChartedTrader at no cost to you.
Open a Hyperliquid account with a 4% fee discount on your first $25M of volume (Vaults and sub-accounts excluded) →If you place a buy limit at 60,005 and the best ask is 60,010, your order will not fill until the ask side moves down to 60,005. If the market moves against you, you may not fill at all.
If you place a market buy for 10 units and the book is thin, you may fill at 60,035 or worse.
The math is the same either way. The difference is whether you are crossing the book or waiting for the book to come to you.
For small orders in deep markets, the difference may be minor. For larger orders in thin markets, the difference can be significant.
When to use a market order
Use a market order when:
- Your order size is smaller than the best level size.
- You need immediate execution.
- You have already estimated the fill price and it is acceptable.
- The book is deep enough to absorb your order without walking multiple levels.
- Your order size is larger than the best level size.
- The next few levels are far apart.
- The book is thin or changing quickly.
- You have not checked the size at each level.
When to use a limit order
Use a limit order when:
- You want to control your maximum or minimum fill price.
- Your order size is larger than the best level size.
- You can accept the risk of not filling.
- You are willing to wait for liquidity to come to your price.
If you place a limit order at the last trade price and expect it to fill immediately, you are making a reading error. The last trade price is not the current best bid or best ask.
How this connects to fees
Slippage and fees are different costs, but they both affect your total execution cost.
A trader can pay a low fee and still have a poor fill if the order walks the book. A trader can pay a higher fee and have a better fill if the order is sized to the available depth.
The Hyperliquid maker vs taker fees guide explains how limit orders can reduce fee exposure. This guide adds the other side: limit orders can also reduce slippage by letting you choose the price at which you are willing to rest.
The best execution is usually a combination of fee awareness and depth awareness. If you only think about fees, you may cross the book and pay slippage. If you only think about depth, you may ignore the fee difference between maker and taker orders.
Common mistakes that make slippage look random
Slippage often looks random because traders do not see the book changing in real time. In reality, most bad fills have a visible cause.
The most common mistakes are:
- Ordering too large for the top of book. The order walks the book.
- Reading the last trade instead of the current book. The last trade is not the current available price.
- Assuming the spread is the only cost. Depth determines how far the price moves after the spread.
- Placing a market order during thin hours. The book may have less size than usual.
- Not checking the size at each level. A tight spread with small size can still produce slippage.
FAQ
What is the difference between spread and slippage?
Spread is the gap between the best bid and the best ask. Slippage is the extra price movement your order causes when it consumes multiple levels of the book.
Does a tight spread mean low slippage?
No. A tight spread only means the first level is close. If the size at that level is small, a larger order can still walk the book and create slippage.
Should I always use a limit order?
Not always. Limit orders control price but may not fill. Market orders fill faster but can create slippage. The right choice depends on your order size, the visible depth, and how urgent the execution is.
How do I estimate slippage before placing an order?
Add the size at each ask level for a buy, or each bid level for a sell, until your order size is covered. Then calculate the weighted average fill price from those levels.
Why did my market order fill at a worse price than the last trade?
Because the last trade is historical. Your market order was matched against the current resting orders, and part of the order may have consumed price levels away from the last trade.
Risk Warning
Risk Warning: Crypto trading involves substantial risk of loss. Never invest more than you can afford to lose. This is not financial advice.Open a Hyperliquid account with a 4% fee discount on your first $25M of volume (Vaults and sub-accounts excluded, as of August 2026): https://app.hyperliquid.xyz/join/RICH888
Continue with Hyperliquid
Browse the Hyperliquid guide hub for the complete user journey.
Continue with Hyperliquid
Official reference: Hyperliquid documentation.