How big should the position actually be? The stop-first sizing math from BloFin Academy's futures risk guide

BloFin Academy's futures risk guide opens with a point most of us learn the hard way: accounts rarely blow up because of a bad coin pick. They blow up because the position was too big for the stop.

The image is the official cover art from that BloFin guide, a dark tablet with three glowing amber candles on a grid. No prices or account data in it.

Size from the stop, not from the balance

The guide's worked example: a 5,000 USDT account, risking 1% per trade, so $50 is the most you're willing to lose. Your stop sits 3% below entry. $50 divided by 3% gives a notional size of about $1,667. With BTC at $70,000 in their example, that's roughly 0.0222 BTC. If the stop hits, you lose the $50 you planned for, not whatever the market decides.

The 1-2% guideline means you could take a long losing streak and still be trading.

Check the liquidation price before you confirm

At 10x, a 10% move against you eats the whole margin. At 20x it's 5%. The guide's rule of thumb: if BTC normally moves 3-5% in a day and your liquidation price sits inside that range, the size or leverage is too aggressive. BloFin shows the liquidation price in the order panel and moves it live as you change leverage, so you can see it before you commit. The guide suggests 2x to 5x for most traders, even though BTCUSDT goes much higher.

Margin mode on purpose

Isolated caps the loss at the margin you assigned to that one position. Cross shares your whole available balance, which pushes liquidation further away but lets one bad trade drain the account. You pick it per position on BloFin. The guide's warning: don't flip a losing isolated trade to cross to rescue it.

Exits set before entry

• Entire-position TP/SL closes everything at market, one per position, and when one side fires the other cancels. Setting both is the OCO setup. Their example: long at $75,000, take profit at $84,700, stop at $71,250.
• Partial TP/SL lets you scale out, for example half at one level and half at another.
• Triggers can use last, mark or index price. The guide recommends mark price for stops because it's harder to wick on one venue.
• Trailing stop: if you're up $3,000 with a $2,000 trail, at least $1,000 is locked in, and the trail keeps following new highs.

Smaller things that add up

Limit orders (Post Only, GTC, IOC, FOK) cost less than market orders as maker fills, but for a triggered stop in a fast market, getting out at market beats not getting out. Funding is exchanged every 8 hours on perps, so a long held through strongly positive funding keeps paying.

The mistakes list from the guide

Trading high leverage without a stop, keeping a mental stop instead of a real one, moving the stop further away when losing, switching to cross mid-loss, and sizing by available balance instead of by risk. The guide also notes a stop is not a guarantee: in a fast or thin market price can gap through it, so leave room between your stop and your liquidation price.