Leverage & Margin
Binance uses a sophisticated risk control system and liquidation model to support high leverage trading by adopting the Maintenance Margin model.
The maximum amount of leverage available depends on the notional value of your position. The larger the position, the lower the leverage.
You can adjust the leverage according to your needs, and all position sizes are calculated based on the notional value of the contract (USDT denominated). Thus, the Initial Margin is determined by the leverage you selected.
The detail information please refer to Binance Official Announcement:
Leverage & Margin of Futures Contracts | Binance Futures
Binance

How to calculate the notional value:

During the holding, the notional value would be changed according to the mark price.
  • USD-M Futures:
a. Opening Notional Value = entry price * size
b. Notional Value of the position = Mark price * size
  • COIN-M Futures:
a. Opening Notional Value= cont * contract multiplier / entry price
b. Notional Value of the position= cont * contract multiplier / mark price
(Cont is the unit for amount, contract multiplier is the face value for each cont. For example, the contract multiplier for BTCUSD perpetual contract is 100, this means 1 cont values 100 USD.)

For contract multiplier information, please refer to Binance Official FAQ: Trading Rules

Notes:
  • If you have open positions in Isolated Margin Mode, you are not allowed to lower the leverage.
  • The maximum position limit of each tier includes both long and short positions.