Free Tool

P&L Calculator

Model any prediction market position — stake, entry price, target exit, and position type. Client-side only. No data leaves your browser.

Position

Stake ($)

Bankroll ($)

Entry price40¢

Target exit / resolution85¢

Your estimated true probability55%

If > entry price, you have positive edge.

Projected outcome · YES

+$112.50

+112.5% return

Shares: 250.0
Payout if win: $212.50
Breakeven: 40¢

Kelly position sizing

Full Kelly

$250

Half Kelly (safer)

$125

Expected value: +$16.88

Client-side only. Excludes platform fees (Kalshi 5–7% of profit; Polymarket ~0.5–1% spread). Past performance ≠ future results.

$0.65 → $1.00

65¢ YES, resolves YES = +54% return on stake

$0.65 → $0.00

65¢ YES, resolves NO = -100% stake (lose all)

Spread matters

Limit orders typically save 2-3¢ vs taking the market

Frequently asked questions

How do you calculate prediction market P&L?

Profit = (exit price − entry price) × shares. If you buy 100 YES shares at $0.65 and sell at $0.80, profit = ($0.80 − $0.65) × 100 = $15.

Does this calculator track real positions?

No — it's a stateless modeling tool. Nothing is stored, sent, or tracked. Run scenarios privately in your browser.

Does the fee structure differ by platform?

Yes. Kalshi takes 5–7% of profit on winning trades. Polymarket charges 0 fee but you pay the spread (~0.5–1%). The calculator shows gross P&L — subtract fees mentally.