Margin trading is a trading with borrowed funds. The idea of such a trading is to borrow money from a broker and trade with funds greatly exceeding trader’s own. This pledge is called margin. Margin funds are measured by the currency of deposit (for instance, US dollar). Margin depends on liquidity of a trading instrument (products).
The essential part of the margin trading mechanism is to provide a leverage.
To calculate margin-based leverage, divide the margin amount by the total value of a transaction. For example, the ratio 1:100 shows that in order you can trade, the balance of your trading account have to be 100 times less than the value of a transaction.