Kalshi vs Polymarket Odds Comparison

Get the same sports game priced on both Kalshi and Polymarket, side by side, with the cheapest side, the price gap and the cross-venue arbitrage cost already worked out. Built for sports traders, odds-screen builders, betting-model developers and AI agents that poll this repeatedly. Every row is matched by real team-code and date data pulled live from both venues at run time, not by guessing - an ambiguous or unmatched game is dropped rather than force-fit.

• One row per matched game - both venues' bid/ask/mid for each team, which venue is cheaper for each side, the price gap, and whether buying the cheapest YES on both teams costs less than $1 before fees.
• Real team matching, not string luck - a static team table (city, nickname, Kalshi ticker code) keeps same-city pairs apart (Giants/Jets, Rams/Chargers, Lakers/Clippers, Yankees/Mets, Cubs/White Sox), and a game only matches when both team codes and the game date agree.
• NFL, NBA, MLB, NHL, filterable by minimum gap or arbitrage-only, with an optional audit view of every unmatched game and why it didn't match.

Example row (from a live run, 2026-09-24)

{
  "league": "NFL",
  "game": "Green Bay Packers vs Atlanta Falcons",
  "start_time": "2026-09-25T00:15:00+00:00",
  "team_a": "Green Bay Packers",
  "team_b": "Atlanta Falcons",
  "kalshi_yes_bid_a": 0.69,
  "kalshi_yes_ask_a": 0.70,
  "kalshi_mid_a": 0.695,
  "kalshi_yes_bid_b": 0.30,
  "kalshi_yes_ask_b": 0.31,
  "kalshi_mid_b": 0.305,
  "polymarket_price_a": 0.695,
  "polymarket_best_bid_a": 0.69,
  "polymarket_best_ask_a": 0.70,
  "polymarket_price_b": 0.305,
  "polymarket_best_bid_b": 0.30,
  "polymarket_best_ask_b": 0.31,
  "gap_a": 0.0,
  "gap_b": 0.0,
  "best_venue_a": "kalshi",
  "best_venue_b": "kalshi",
  "cheapest_ask_a": 0.70,
  "cheapest_ask_b": 0.31,
  "arb_cost": 1.01,
  "arb_opportunity": false,
  "arb_edge": -0.01,
  "thin_market": false,
  "kalshi_event_ticker": "KXNFLGAME-26SEP24ATLGB",
  "polymarket_event_slug": "nfl-atl-gb-2026-09-25",
  "kalshi_url": "https://kalshi.com/markets/kxnflgame",
  "polymarket_url": "https://polymarket.com/event/nfl-atl-gb-2026-09-25",
  "kalshi_volume_a": 1281182.14,
  "kalshi_volume_b": 628492.21,
  "polymarket_volume": 273090.01,
  "polymarket_volume_24h": 145713.48,
  "match_confidence": "ticker_code",
  "matched": true,
  "scraped_at": "2026-09-24T07:42:25+00:00"
}

This particular game is a good example of why the before-fees caveat below matters: both venues price it almost identically (a 0-cent gap on both sides), so arb_cost lands at 1.01 - one cent above $1, not an opportunity. Real, liquid games are usually efficiently priced across venues; the gaps worth screening for show up more in thinner markets.

Input

• leagues - NFL, NBA, MLB, NHL (default: all four). NBA games start appearing once Polymarket opens its season markets; until then NBA simply contributes zero rows.
• minGap - only keep a game if at least one side's price gap is at least this big (default 0, keeps everything).
• onlyArbitrage - only keep games where arb_opportunity is true (default false). Can legitimately return zero rows.
• includeUnmatched - also emit an uncharged matched: false row for every Kalshi game that had no confident Polymarket match, with an unmatched_reason (default false).
• maxGames - cap on matched rows returned, soonest game first (1-500, default 100).

Output

One JSON row per matched game (see the example above), plus optional unmatched-audit rows when includeUnmatched is on. Download the dataset as JSON, CSV, Excel or HTML from the Apify Console, or pull it through the API.

Pricing

Pay-per-event: $2 per 1,000 matched games (the game event, one per row in the main output) plus $0.001 per run start. Unmatched-audit rows (includeUnmatched) are never charged.

Before you trade on this

arb_opportunity and arb_cost are computed before fees and slippage: Kalshi charges a trading fee on top of the quoted price, and Polymarket's quoted best bid/ask already has a spread that can move against you between quote and fill. Treat this as a screen for where to look closer, not a guaranteed risk-free trade.

thin_market is true when the cheapest leg on either side has never traded on that venue (zero lifetime volume). An "arbitrage" on such a row is usually a stale or tiny quote, so check kalshi_volume_a/_b and polymarket_volume before acting. Filter on thin_market: false to see only edges that have real trading behind them.

Not affiliated with Kalshi or Polymarket.