Short Selling P&L Calculator

What Is Short Selling?

Short selling is a strategy where you borrow shares from a broker and sell them immediately, hoping the price will fall. Later, you buy the shares back (this is called “covering”) at a lower price, return them to the broker, and pocket the difference.

Example: You borrow 100 shares at $100 and sell them. The price drops to $70. You buy 100 shares at $70 to return them. Profit: ($100 − $70) × 100 = $3,000.

The Formulas

P&L (before commissions): P&L = (Borrow Price − Cover Price) × Shares

P&L Percentage: P&L % = (Borrow Price − Cover Price) ÷ Borrow Price × 100

Break-Even Price: Break-Even = Borrow Price − (Total Commission ÷ Shares)

Maximum Profit: Max Profit = Borrow Price × Shares (if stock falls to $0)

Maximum Loss: Theoretically unlimited — if the stock rises from $100 to $500, you lose $400 per share.

Margin Requirements

Regulators require short sellers to hold margin — collateral in case the trade goes wrong. Under Regulation T (US), you must maintain at least 150% of the position value in your account:

• If you short $10,000 worth of stock, you need $15,000 in your account.
• As the stock rises, margin calls force you to add funds or close the position.

The Short Squeeze Risk

The most dangerous scenario for short sellers is a short squeeze. If a heavily shorted stock rises sharply, shorts scramble to cover (buy back), pushing the price even higher — trapping other shorts in a feedback loop.

The most famous example: GameStop (GME) in January 2021. Retail traders on Reddit coordinated buying that sent GME from ~$20 to a peak of $483 within days — destroying billions in short positions.

Borrow Fees for Hard-to-Borrow Stocks

Shorting popular stocks (ETFs, large-caps) costs very little in borrow fees. But shorting hard-to-borrow (HTB) stocks — small-caps, meme stocks, heavily shorted names — can cost 10%–100%+ annually in borrow fees. These fees eat into profits significantly on longer holds.

The Uptick Rule

Since 2010, the SEC’s Alternative Uptick Rule restricts short selling when a stock drops 10%+ in a single day. This reduces downward pressure during sharp selloffs.

Who Uses Short Selling?

• Hedge funds: Hedging long exposure; profiting from overvalued stocks.
• Arbitrageurs: Exploiting price discrepancies between related securities.
• Speculators: Pure directional bets on stocks they believe will fall.

Worked Example

• Short entry (borrow price): $100.00
• Cover price (exit): $70.00
• Shares: 100
• Commission each way: $5.00
• P&L (gross): ($100 − $70) × 100 = $3,000
• Total commission: $5 + $5 = $10
• Net P&L: $3,000 − $10 = $2,990
• P&L %: $30 ÷ $100 × 100 = 30%
• Break-even price: $100 − ($10 ÷ 100) = $99.90
• Margin required (150%): $100 × 100 × 1.5 = $15,000