We present a calculation of the decay rate of the electroweak vacuum, fully including all gravitational effects and a possible nonminimal Higgs-curvature coupling
ξ
, and using the three-loop Standard Model effective potential. Without a nonminimal coupling, we find that the effect of the gravitational backreaction is small and less significant than previous calculations suggested. The gravitational effects are smallest, and almost completely suppressed, near the conformal value
ξ
=
1
/
6
of the nonminimal coupling. Moving
ξ
away from this value in either direction universally suppresses the decay rate.