Cost basis is the reference point for a futures position’s profit and loss, and traders searching for cost basis usually want one practical answer: which number on the screen tells them whether the position is up or down. In perpetual futures, that reference is the position’s entry, while the live reading comes from comparing it with the mark price. This guide shows how to read that correctly for linear, USDT-margined perpetuals, especially once leverage, margin, liquidation, and funding enter the picture. You can try the mechanics with play money on ZK Futures, where a new account starts with 1,205.50 test USDT.
What cost basis means in a futures position
Cost basis in a futures position means the entry reference used to measure profit and loss. For traders searching for cost basis, the key point is simple: in a linear, USDT-margined perpetual, it is the position’s entry price, or average entry price if the current position was built in more than one fill.
That differs from spot trading. In spot, cost basis usually means what you paid to own an asset. In a perpetual future, you are reading a contract position, so cost basis is the price reference the terminal uses to value that position as the market moves.
Three terms help keep the screen readable:
- Entry price is the average price at which the current position was opened.
- Mark price is the reference price used to value the open position and test liquidation conditions; see how fair price works.
- Unrealized PnL is the profit or loss on the open position before it is closed.
So cost basis is not a cash figure in the account. It is also not the margin locked for the trade, and it is not the full size of the position. The full size is the position’s notional value, while margin is the smaller amount set aside to support it.
When you read a terminal, start with the open positions in the portfolio. Find the entry price first. That is the anchor. The mark price tells you where the position is being valued now, and unrealized PnL shows the difference in USDT.
How cost basis connects to unrealized PnL
Cost basis is the entry reference for the position, and unrealized PnL is the live gain or loss calculated from that reference against the mark price. The mark price is the valuation price the terminal uses for an open position, and unrealized PnL is the result shown before the position is closed.
For a long, the reading improves when mark is above entry and worsens when mark is below entry. For a short, it is the reverse: lower mark helps, higher mark hurts. That is why traders who search for cost basis in futures usually need one practical answer: compare entry with mark, not entry with the last trade.
The last trade can be noisy. A quick move through the book, a wide bid-ask spread, or a burst of order flow can print a price that does not tell you the full state of your open position. A liquidity sweep can do the same. Your screen may show that print, but the running PnL is tied to mark.
That matters most when you are checking a position quickly. On a market list, you might notice a move in BTC, ETH, SOL, DOGE, or PEPE and then open the position panel to see whether your trade is actually up or down. The correct read is:
- entry tells you the cost-basis reference
- mark tells you the current valuation
- unrealized PnL shows the difference in USDT
If you record trades in a trading journal, keep those three fields together. They show what the market has done to the open position so far, before closing turns the result into a realized one.
Margin, leverage, and why cost basis is not cash at risk
Margin is the play-money collateral set aside to support an open futures position. Leverage is the ratio that lets a trader control a larger position value with a smaller margin amount. Cost basis is different from both: it is still only the entry reference used to measure PnL.
That distinction matters because a position can have one entry price and a very different amount of cash at risk. In isolated margin, only the margin assigned to that position is exposed to liquidation. The initial margin equals position value divided by leverage.
Example: a 1,000 USDT position at 10x leverage locks 100 USDT of margin. The position still rises or falls on the full 1,000 USDT notional value, not on the 100 USDT margin. So when traders ask whether cost basis is their risk, the answer is no: entry tells you where PnL starts, while margin tells you how much support the position has.
Leverage changes how quickly losses eat through that support:
- at 10x, a 10% adverse move uses up the initial margin
- at 100x, a 1% adverse move does
- at 2x, a 50% adverse move does
This is why higher leverage leaves less room for error. A position can look small in margin terms but still react like a much larger trade.
For day-to-day risk reading, pair margin with the account view that records funding payments in the play-money wallet. If a market is moving fast, a liquidation heatmap can add context. And if you want a predefined exit level, a stop order can limit damage before liquidation.
Liquidation price: the number every leveraged trader should read
Liquidation price is the mark-price level where a position’s equity falls to maintenance margin and the system closes it. Equity means the margin assigned to the position plus unrealized PnL. Maintenance margin is the minimum support required to keep the position open, here 0.5% of the position value at the mark price.
For this setup, the formulas are:
- long liquidation price = entry price x (1 - 1/leverage) / (1 - 0.005)
- short liquidation price = entry price x (1 + 1/leverage) / (1 + 0.005)
These formulas show why leverage changes risk so sharply. With the same entry price, 100x puts the liquidation level much nearer than 10x, and 10x puts it nearer than 2x. A small adverse move can therefore matter a lot when leverage is high.
Two details are easy to miss:
- liquidation is checked against the mark price, not the last trade
- the maintenance test uses position value at the current mark price, so the threshold moves with the market
A quick example helps. Suppose a trader opens a long at 10x leverage. Roughly speaking, a 10% adverse move uses up the initial margin, but liquidation comes before the entire margin is gone because the position must still satisfy the 0.5% maintenance requirement.
In ZK Futures, balances are play money, and under isolated margin the loss on one position is capped at that position’s margin. That cap does not make liquidation harmless: it still means the position is closed and the margin assigned to it is exhausted.
Funding, execution, and other numbers that affect what you see
Funding is a periodic payment between longs and shorts designed to keep perpetual futures aligned with the underlying market. The direction rule is simple: at a positive rate longs pay shorts, and at a negative rate shorts pay longs.
This payment does not change the entry-based cost basis of the position itself. Your entry price still anchors unrealized PnL. But funding does change account results over time, so it belongs in the total reading of what a position has cost or returned so far. For example, a funding rate of 0.01% on a position worth 10,000 USDT is a payment of 1 USDT per settlement.
Platforms can settle funding on different schedules. In ZK Futures funding is settled every 30 seconds in the demo, while many exchanges settle every 8 hours and some every hour. Each settlement is capped at 0.1% of the position value.
Execution is the process by which an order is matched against orders resting in the order book. Order books match by price-time priority: the best price goes first and, at the same price, earlier orders go first.
Common questions about cost basis
If I build a position in several fills, what is the cost basis?
For an open perpetual position, cost basis is usually the average entry price of the size that is still open. If you enter in several fills, the platform combines them into one entry reference for the current position. That matters because the PnL reading uses the open position’s average entry, not the price of just the first fill or the most recent one.
Is cost basis the same for longs and shorts?
Yes. Cost basis still means the entry reference of the position. What changes is how price movement affects the result:
- a long benefits when mark is above entry
- a short benefits when mark is below entry
So the definition stays the same, but the direction of favorable and unfavorable movement flips.
Can funding make a position feel profitable or unprofitable even if price barely moved?
Yes. Funding is separate from the entry reference, but it still changes the running account result. In this demo, funding settles every 30 seconds, and each payment is capped at 0.1% of the position value per settlement. A position can therefore show little change from price while funding payments still add up in the background.
What number should I trust during a fast market?
Use the mark price for valuation and risk checks. Fast trading can produce noisy prints, but the mark price is the reference used to value the position and test whether it has reached liquidation conditions. If you are trying to understand whether the position is healthy, the mark-based reading is the one that matters.
What is the safest way to learn this without real funds?
Practice with play money first. On ZK Futures, every balance is play money, a new account starts with 1,205.50 test USDT, and there are no deposits or withdrawals of real funds. That makes it a safer place to watch how entry, mark, funding, and liquidation interact before using leveraged products elsewhere.
Reading cost basis correctly in practice
When you check cost basis on a futures screen, read the fields in order instead of jumping straight to the PnL number. That keeps the position context clear.
- Entry price: the reference for the open position
- Mark price: the price used to value it now
- Unrealized PnL: the difference in USDT
- Margin locked: the play-money support assigned to the trade
- Liquidation price: the mark-price level where the position would be closed
One more step matters: look at recent funding. Funding does not reset cost basis, but it does change the running account result between entry and exit. On ZK Futures, every balance is play money, and funding settles every 30 seconds in the demo.