Buy edge vs sell edge
A buy edge means Kalshi is pricing an outcome cheaper than the de-vigged book consensus — you're getting a bargain. A sell edge means Kalshi is overpriced, meaning you can either sell YES on Kalshi (lock in profit if the market reverts) or simply bet the same side at the books instead.
What threshold is actionable?
- Under 1.5% — typically noise. Bid/ask spread + de-vig assumptions absorb most of this.
- 1.5–3% — small edge. Worth tracking but usually not enough to overcome variance.
- 3–5% — actionable. SportsBookISH's default Pro alert threshold sits here.
- 5–10% — rare, worth investigating. Often a sign of a stale book line or fresh news.
- 10%+ — almost always a data anomaly. Double-check the market URL on Kalshi before betting.
Best book vs books median
Books median is the conservative target — the middle of the de-vigged distribution across all books. Best book is the most aggressive target — the cheapest book on that specific side. If you have accounts at multiple sportsbooks, comparing Kalshi to the best book reveals the maximum arbitrage potential.
Common edge traps
- Stale book lines — a sportsbook hasn't updated after a major injury. Cross-check breaking news before betting an outsized edge.
- Illiquid Kalshi markets — wide bid/ask spread (>5¢) means the mid-price is unreliable. Stick to markets with tight spreads.
- Scheduled line moves — books may move in unison ahead of a known catalyst (lineup announcement, weather report). Edges close fast in these windows.
- Stale Kalshi quotes — our data plane refreshes every 5 minutes. For sub-minute precision, click into the event page where you'll see exact Kalshi bid/ask + last trade.
- Asymmetric vig — books shade one side more than the other on heavy public bets. The de-vig assumption (split evenly) breaks down; use 'best book' instead.
Building a system
Sustainable edge betting requires: (1) consistent threshold — pick 3% and stick to it; (2) bankroll management — never more than 2% of bankroll on any one edge; (3) record-keeping — track every bet and compare predicted vs actual edge accuracy. SportsBookISH's daily digest gives you the day's top 3 buy + sell candidates; set alerts on Pro/Elite for real-time delivery.