Required margin is the notional size of the position divided by the leverage. A 100,000 euro position in EUR/USD at 1.1000 is 110,000 dollars of exposure. At 30:1 the margin is about 3,667 dollars. At 500:1 it is 220 dollars. The exposure is the same. Only the cash held back changes.
European and UK retail rules cap major forex leverage, often at 30:1. That cap is a conduct rule for a client category. It is not a statement that the broker’s professional or offshore entity offers the same ratio, and it is not a measure of the firm’s quality. Market Explain leaves a broker’s maximum leverage blank until the figure is read from that entity’s own disclosure.
Margin level is equity divided by used margin. If equity falls through the broker’s close-out level, positions are reduced or closed whether or not the original idea still makes sense. Negative-balance protection, where it exists, stops a retail account going below zero. It does not stop the account reaching zero.
A useful check before increasing size is the loss at the stop, not the maximum leverage on the website. Position size is money at risk divided by the pip value of the stop. Leverage only tells you whether the margin will fit.