Since WCX uses an isolated margin system, each position's liquidation price is known ahead of time. You can see an order or position's liquidation price in its Details panel.
A position is liquidated when it loses 80%.
You have the following buy position on EUR/USD:
Size: 100 BTC
Entry price: 1.12
Margin: 1 BTC
Your liquidation price is the price at which your position loses 80% of its 1 BTC margin = 0.8 BTC. Since it's a 100 BTC position, it will lose 0.8 BTC when price drops 0.8% from your entry price. So the position's liquidation price is 1.11104.
1.12 * (1 - 0.8%) = 1.11104
When your position is liquidated, it loses 100% of its margin. In the above example, you would lose 1 BTC if your liquidation price is hit. The 20% difference from the 80% loss trigger price is used as safety risk measure for fast-moving markets.