A 64-leg parlay on one dollar would only pay out if every single pick hits, so the amount depends entirely on the odds you used for each match. If you mean a simple even-money assumption for every leg, the payout would be 2642^{64}264 dollars, which is about $18.4 quintillion on a $1 stake.

How that works

  • Even-money legs mean each win doubles the stake.
  • After 64 straight wins, the multiplier is 2642^{64}264.
  • So 1×264=18,446,744,073,709,551,6161\times 2^{64}=18,446,744,073,709,551,6161×264=18,446,744,073,709,551,616.

Real-world catch

  • Tennis favorites in a Grand Slam usually are not all even money.
  • If you bet the actual eventual winner of each round-of-128 match, the true payout could be much higher or lower depending on the odds for each individual match.
  • Also, the round of 128 at Roland Garros 2026 has already been played in real life, so this is a hypothetical payout question rather than a live betting result.

TL;DR

At even odds, a $1 64-leg parlay would be worth about $18.4 quintillion if it somehow hit all 64 matches.