Ukraine wins when it has 1:3 ratio of artillery shells to Russia. Which means Russia needs more than three times more shells to make progress on the front. It would seem they're getting better now with jamming and drones, but I think they currently are around this ratio, and Russia is not doing much progress.

Nato has more and much more advanced stuff than Ukraine. So I don't know if 1:6 would be enough, but Europe has a lot of margin to increase its production and don't need so much more than that to stop Russia.