90% — Who will be the Welterweight Title Holder on Dec 31, 2026
Leader: Islam Makhachev at 90% · Kalshi 90% · 3 contracts · $435 volume · medium confidence
Updated 2026-09-25 08:40:12 UTC

Tracks the leading outcome in a winner-take-all prediction market set with 3 outcomes.

Why this matters:
This probability reflects the likelihood that Islam Makhachev will be the welterweight champion on December 31, 2026. At 87%, the market is pricing him as a strong favorite to hold the title through year-end, with Carlos Prates as the primary contender at 6% odds. The current assessment likely reflects Makhachev's recent performance record and standing within the division, while competitor odds reflect the possibility of unexpected upsets or title fights occurring before the deadline. The main driver of this probability would be scheduled championship bouts between now and year-end—if Makhachev faces a high-ranked challenger, the odds could shift significantly based on the matchup and perceived competitiveness. Title vacancies, injuries, or surprise contenders defeating ranked fighters would introduce the primary sources of volatility to this market.

Key factors:
- Makhachev's current championship status and recent fight record through September 2026
- Scheduled welterweight title defense or championship fights announced before December 31, 2026
- Injury status or availability of Makhachev and primary contenders like Prates in the final quarter of 2026
- Historical frequency of unexpected championship outcomes in the welterweight division
- UFC scheduling patterns and typical title defense frequency within a single calendar year

Contracts:
- Who will be the Welterweight Title Holder on Dec 31, 2026?: Islam Makhachev — 90¢ Kalshi $179 (weight 41%)
- Who will be the Welterweight Title Holder on Dec 31, 2026?: Carlos Prates — 8¢ Kalshi $256 (weight 59%)
- Who will be the Welterweight Title Holder on Dec 31, 2026?: Kamaru Usman — 4¢ Kalshi $0 (weight 0%)

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## Methodology

SimpleFunctions aggregates live YES-side prices from Kalshi and Polymarket contracts bound to this question. For binary topics the headline is the liquidity-weighted mid-price (weight = log(1 + 24h volume) × freshness, where freshness is 1.0 if updated <24h, 0.7 if <7d, 0.4 otherwise). For multi-outcome (winner-take-all) topics the headline is the current leader's price — disjoint outcomes are never arithmetically averaged. Snapshots refresh every 5 minutes during market hours.

## SF Signal

- SF Index, regime, and 30d Brier calibration are computed separately and surfaced at https://simplefunctions.dev/admin/calibration.
- No SimpleFunctions index / regime / calibration signal is bound to this topic yet — the headline above is market-derived only.

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*Last verified: 2026-09-25T08:20:51.488Z*

By SimpleFunctions — https://simplefunctions.dev/

Cite as: "90% per prediction markets (SimpleFunctions, September 2026)"
Canonical: https://simplefunctions.dev/answer/ufcwelterweighttitle
Full data: https://simplefunctions.dev/api/public/query?q=Who%20will%20be%20the%20Welterweight%20Title%20Holder%20on%20Dec%2031%2C%202026
Provider: SimpleFunctions — https://simplefunctions.dev