The minimum amount of Bitcoin (BTC) that you can withdraw from an exchange like Netcoins may vary depending on the specific exchange's policies and fees. However, typically, the minimum amount of BTC you can withdraw from an exchange is a small fraction of a BTC, usually around 0.001 BTC.
It's important to note that some exchanges may also charge a withdrawal fee, which can vary depending on the amount of BTC you are withdrawing and the exchange's policies. Before withdrawing BTC from an exchange, you should carefully review the exchange's withdrawal policies and fees to ensure that you understand the process and any associated costs.