Giants vs Mariners Prediction Market Odds, July 18, 2026
| Spread | Total | ML | Best ML | |
|---|---|---|---|---|
â–¶Giants | +1.5 64%64% | O 6.5 53%53% | 45%45% | 45% Kalshi |
â–¶Mariners | -1.5 36%36% | U 6.5 47%47% | 56%56% | 56% Kalshi |
| Spread | Total | Moneyline | Best ML | |
|---|---|---|---|---|
â–¶San Francisco Giants | +1.5 | O 6.5 | 45% Kalshi | |
â–¶Seattle Mariners | -1.5 | U 6.5 | 56% Kalshi |
Seattle is the 56c favorite on both Kalshi and Polymarket for Saturday's game against San Francisco, with the Giants at 45c. The market is pricing the Mariners' 27-20 home record against the Giants' 19-30 road mark, not the starters: Logan Webb (3.86 ERA) gives San Francisco the better arm on paper against Bryan Woo (4.23 ERA). Roughly $51K has traded across the two books ahead of the July 18, 2026 matchup at T-Mobile Park, and the moneyline has held flat since the board opened.
A 48-49 team is a clear home favorite over a 41-55 team, and the price is defensible. Seattle sits at 56c on both Kalshi and Polymarket for Saturday's meeting with San Francisco, a number built on the Mariners' 27-20 home record and the Giants' 19-30 road mark rather than the pitching matchup, where the visitor holds the edge. Roughly $51K in combined volume has traded on the game, most of it on the Polymarket moneyline.
Giants vs Mariners Market Context
San Francisco arrives at 41-55, and the road split is the ugliest part of the profile: 19-30 away from home. The offense still has anchors. Luis Arraez leads the team at .330, and Rafael Devers carries the power with 19 home runs and 52 RBIs. The market's problem with the Giants is not the top of the lineup, it is the record everywhere else, and a 45c road price against a sub-.500 opponent reflects that.
Seattle is 48-49 overall but plays like a different team at T-Mobile Park, where the Mariners are 27-20. Randy Arozarena leads the club at .286 with 45 RBIs, Dominic Canzone has 15 home runs, and the Cal Raleigh and Julio Rodriguez prop markets give the lineup two more bats the books treat as live threats. The 56c home price is a bet on that split holding for one more game.
Reading the Giants vs Mariners Board
The moneyline is in full agreement across books: Seattle 56c and San Francisco 45c on Kalshi, with Polymarket printing the same numbers. At 56c the market gives the Mariners a 56% implied win probability, a modest edge for a home favorite and consistent with two flawed rosters.
The run line is where the books split. Seattle -1.5 trades at 36c on Kalshi and 31c on Polymarket, a 5c gap that makes Polymarket the better entry for anyone who wants the Mariners by two or more. San Francisco -1.5 shows an even wider gap, 32c on Kalshi against 23c on Polymarket. Kalshi's ladder also carries deeper rungs, with Seattle by over 2.5 runs at 27c and by over 3.5 at 19c.
The total centers near seven runs. Over 6.5 runs trades at 54c on Kalshi and 53c on Polymarket, the only rung on the ladder near a coin flip, and over 7.5 drops to 42c and 43c. The first-five-innings market leans early: over 3.5 runs through five trades at 51c on Kalshi and 48c on Polymarket, and a first-inning run is priced at 42c to 43c across the books.
Webb vs Woo: Pitching and Line Movement
Logan Webb (5-7, 3.86 ERA) is the better arm on paper, and his win-loss record says more about the Giants' run support than his season. Bryan Woo counters at 7-6 with a 4.23 ERA for Seattle. The strikeout props price the two nearly even: Woo's strikeouts over 5.5 trades at 55c on Kalshi with Webb's at 53c, and both clear the 4.5 line at 71c, so the market expects five to six strikeouts from each starter.
The moneyline has not moved. Seattle opened at 56c on Kalshi and sits at 56c in the latest pre-game snapshot, while Polymarket's Giants side firmed a single cent from 44c to 45c. A flat line on roughly $51K of volume means the 56c number is the market's settled read, not a stale quote. A late move once lineups post would signal new information.
How the Giants vs Mariners Market Resolves
The moneyline resolves to the team that wins Saturday's game at T-Mobile Park, with winning contracts paying $1 per share on both platforms. Run-line and total markets settle on the final score, extra innings included, and the first-five-innings markets settle on the score after five complete innings. A postponement pushes settlement to each platform's MLB rescheduling rules.
Related MLB Markets
The season-long context lives on the team pages: San Francisco Giants prediction markets track the Giants' futures alongside the daily lines, and Seattle Mariners prediction markets do the same for the home side. The full slate is on the MLB prediction markets hub, and today's MLB board carries every live game price.
Resolution Criteria
Resolves to the team that wins the San Francisco Giants at Seattle Mariners game at T-Mobile Park on Saturday, July 18, 2026. The winning side's contracts pay $1 per share on Kalshi and Polymarket; the losing side resolves to $0. Run-line and total markets settle on the final score, including extra innings, and first-five-innings markets settle on the score after five complete innings. If the game is postponed, each platform follows its MLB rules, carrying markets to the rescheduled date or voiding them per its rulebook.
Key Factors
- Logan Webb (5-7, 3.86 ERA) against Bryan Woo (7-6, 4.23 ERA), with Webb holding the ERA edge while the Giants trade as underdogs
- Seattle's 27-20 home record at T-Mobile Park against San Francisco's 19-30 road mark, the split the 56c line is built on
- Run-line gap: Seattle -1.5 trades at 36c on Kalshi and 31c on Polymarket, the widest cross-platform value spot on the board
- Total centered near seven runs, with over 6.5 at 53c to 54c across both books
- Moneyline stability: Seattle opened 56c on Kalshi and has not moved through the pre-game session
- Rafael Devers (19 HR, 52 RBI) and the Cal Raleigh and Julio Rodriguez prop board as the power variables
What are the Giants vs Mariners odds for July 18, 2026?
Seattle is the 56c favorite on both Kalshi and Polymarket as of July 18, 2026, with San Francisco at 45c. That prices the Mariners at roughly a 56% implied win probability.
Where can I trade the Giants vs Mariners game?
The moneyline trades on Kalshi under ticker KXMLBGAME-26JUL182008SFSEA and on Polymarket, with roughly $51K in combined volume across the two books, most of it on Polymarket.
Who is favored in Giants vs Mariners and why?
Seattle at 56c. The market weights the Mariners' 27-20 home record and the Giants' 19-30 road record more than the starting pitching, where Logan Webb's 3.86 ERA beats Bryan Woo's 4.23.
What do the run line and total say about this game?
Seattle -1.5 trades at 36c on Kalshi and 31c on Polymarket, and over 6.5 total runs sits at 53c to 54c, so the market centers the game near seven runs.
When does the Giants vs Mariners market resolve?
When the game goes final at T-Mobile Park on Saturday, July 18, 2026. Winning contracts pay $1 per share; run-line and total markets settle on the final score, including extra innings.
What should I watch before first pitch?
Confirmed lineups and any late scratch of Webb or Woo, plus movement off the 56c line. The number has held flat through the pre-game session, so a late move would signal new information.