Perpetual futures have become the dominant trading instrument in the cryptocurrency market. Unlike traditional financial products, they feature unique mechanics that can be challenging to grasp. Many traders use them regularly without fully understanding how key metrics are calculated. This guide breaks down the core concepts—margin, profit and loss, and liquidation price—using clear formulas and practical examples.
Understanding Perpetual Futures: Key Concepts
Perpetual futures, often called "perpetual contracts," combine elements of traditional futures with no expiration date. This allows traders to hold positions indefinitely, provided they maintain sufficient margin. Unlike traditional futures, which settle on a specific date, perpetual contracts use a funding rate mechanism to keep their price aligned with the spot market.
Two primary types exist:
- Linear (USDT-Margined) Contracts: Quoted and margined in USDT. Profits and losses are calculated in USDT.
- Inverse (Coin-Margined) Contracts: Quoted in USDT but margined in the base cryptocurrency (e.g., BTC). P&L is calculated in the base coin.
Linear contracts are generally more intuitive for beginners, as they allow trading multiple assets using a single margin currency.
How Margin Calculation Works
Margin is the collateral required to open and maintain a leveraged position. The amount depends on the contract type, leverage, and position size.
Linear Contracts
The formula for calculating margin in linear contracts is:
Margin = (Contract Face Value × Number of Contracts × Mark Price) / Leverage
Example:
- Buy 5 BTC contracts with a face value of 0.1 BTC each.
- Mark Price: $20,000
- Leverage: 2x
- Margin = (0.1 × 5 × 20,000) / 2 = 5,000 USDT
Inverse Contracts
For inverse contracts, the formula is:
Margin = (Contract Face Value × Number of Contracts) / (Leverage × Mark Price)
Example:
- Buy 100 contracts with a face value of 100 USDT each.
- Mark Price: $20,000
- Leverage: 2x
- Margin = (100 × 100) / (2 × 20,000) = 0.4 BTC
At the mark price of $20,000, 0.4 BTC is equivalent to 5,000 USDT, demonstrating consistency between contract types.
Calculating Profit and Loss
Profit and loss calculations differ between linear and inverse contracts due to their valuation methods.
Linear Contracts
- Long Position P&L: (Exit Price − Entry Price) × Face Value × Number of Contracts
- Short Position P&L: (Entry Price − Exit Price) × Face Value × Number of Contracts
Example (Long):
- Entry: $20,000 | Exit: $25,000
- Face Value: 0.1 BTC | Contracts: 5
- P&L = (25,000 − 20,000) × 0.1 × 5 = 2,500 USDT
Inverse Contracts
- Long Position P&L: (1/Entry Price − 1/Exit Price) × Face Value × Number of Contracts
- Short Position P&L: (1/Exit Price − 1/Entry Price) × Face Value × Number of Contracts
Example (Long):
- Entry: $20,000 | Exit: $25,000
- Face Value: 100 USDT | Contracts: 100
- P&L = (1/20,000 − 1/25,000) × 100 × 100 = 0.1 BTC
At the exit price of $25,000, 0.1 BTC equals 2,500 USDT, matching the linear contract result.
Inverse contracts exhibit non-linear P&L curves due to the inverse relationship with price changes.
Liquidation Price Mechanics
Liquidation occurs when losses exhaust the margin balance. The formulas below help estimate liquidation prices.
Linear Contracts
- Long Position Liquidation Price: Entry Price × (1 − 1/Leverage)
- Short Position Liquidation Price: Entry Price × (1 + 1/Leverage)
Example (Long, 2x Leverage):
- Entry Price: $20,000
- Liquidation Price = 20,000 × (1 − 1/2) = $10,000
Inverse Contracts
- Long Position Liquidation Price: Entry Price × (1 − 1/(Leverage + 1))
- Short Position Liquidation Price: Entry Price × (1 + 1/(Leverage − 1))
Example (Long, 2x Leverage):
- Entry Price: $20,000
- Liquidation Price = 20,000 × (1 − 1/3) ≈ $13,333
A key advantage of inverse contracts is that short positions with 1x leverage never liquidate, making them popular for certain strategies.
👉 Explore advanced trading strategies
Frequently Asked Questions
What is the difference between linear and inverse contracts?
Linear contracts use USDT for margin and P&L, simplifying multi-asset trading. Inverse contracts use the base cryptocurrency (e.g., BTC) for margin, with P&L calculated in the base coin.
How does leverage affect liquidation risk?
Higher leverage increases liquidation risk by reducing the price movement needed to wipe out margin. For example, 50x leverage long liquidates after just a 2% price drop.
Can perpetual contracts be held indefinitely?
Yes, but traders must manage funding payments, which are periodic fees paid between long and short positions to maintain price alignment with spot markets.
Why do inverse contracts have non-linear P&L?
Inverse contracts calculate P&L based on the inverse of price changes. This creates a convex payoff curve, where gains increase slower than linear contracts during rallies but losses accelerate during declines.
What factors influence liquidation besides price?
Liquidation depends on margin balance, leverage, and mark price. Volatile markets or low liquidity can cause sudden liquidations if the mark price briefly touches the liquidation threshold.
Is trading perpetual contracts riskier than spot trading?
Yes, leverage magnifies both gains and losses. Proper risk management, including stop-loss orders and margin monitoring, is essential.
Conclusion
Understanding margin, profit and loss, and liquidation mechanics is crucial for successful perpetual futures trading. Linear contracts offer simplicity, while inverse contracts provide unique advantages for specific strategies. Always verify contract specifications with your exchange, as face values and formulas may vary. Practice with small positions and low leverage to build confidence before scaling up.