Why your real profit is smaller than it looks
A trade isn't profitable just because the price moved your way. Three costs sit between the gross move and your wallet: fees (charged on the position notional when you open and again when you close), funding (paid every interval you hold a perpetual), and slippage (the gap between the price you wanted and the price you got). On a small move with high leverage, these can eat most of the gain — or turn a "winner" into a loss.
Want just the funding piece? Use the funding calculator. Sizing a trade from risk first? See the position size calculator, and check your liquidation price before you enter.
FAQ
Are fees really that significant? Round trip on a leveraged position they often exceed the funding cost, and on scalps they can be the difference between green and red.
What fee should I use? Use your exchange's taker fee for market orders (commonly ~0.04–0.06% on futures) or the maker fee for limit orders. Lower with fee tiers or referral discounts.