Average price calculator

• The average price is everything you've paid divided by the coins you hold. If you enter the amount in USDT, each entry gives its value divided by its price in coins; if you enter it in coins, it's used as is.
• In a futures trade, the amount in USDT is the order size (the notional), not the margin. With isolated margin and the same leverage on every entry, the position liquidates as if you had opened it all at the average price.
• It doesn't include fees. The liquidation is an approximation: each exchange uses its own margin table and the mark price.

Because it weighs more where you bought more coins. If you buy the same amount in USDT at two prices, you get more coins at the lower one, and the average ends up closer to the lower price than the plain average of the two.

With isolated margin, if each entry brings its own margin, no: the liquidation moves down with the average price, although the position is bigger and the same move costs you more. What can happen is that an entry comes too late: if the price has already passed the liquidation of what you had, the position doesn't survive until then. The calculator warns you.

Yes. Leave the leverage empty: you get the average price and how much the price has to rise from your last buy to get back to it.