What kill ratio would Nazi Germany need in 1945 to win?

Germany was starved for resources and in a bad strategic position from the very first day of WWII. Winning by attrition (a.k.a. "kill ratios") was never really an option. The whole idea for Germany was to win in a series of quick raids, using surprise and (hopefully) superior training and tactics to win strategically before economic factors took hold. This worked in Poland 1939, in Norway and France 1940, in Greece 1941... but those campaigns (plus the unsuccessful Battle of Britain) had blunted the spear, so to speak, and so it didn't work in Russia in 1941.

From there onwards, it turned into a war of attrition. In such an environment, your "kills" vs. enemy "kills" do not paint a correct picture. You have to look at two separate ratios:

• Own losses vs. own replacement capabilities, and
• enemy losses vs. enemy replacement capabilities.

To be in a "winning" position, you need...

• your own losses not exceeding your own replacement capabilities (i.e. "not losing"), and
• enemy losses exceeding enemy replacement capabilities (i.e. "winning").

That was a losing proposition for Germany even in 1942, indicated by the fact that their 1942 offensive in the east (Fall Blau) was no longer an attempt to actually defeat the Russian army, but a desperate bid for the resources of the Caucasus region.

Two and a half years later, in 1945, Germany...

• was fielding Hitler Youth and Volkssturm units as they rapidly ran out of men in the proper age bracket to recruit;
• did send up pilots who hardly knew how to control their aircraft, as they did not have the fuel to train them properly;
• had its surface fleet annihilated and lost the Atlantic harbors, the U-Boats retreating to the North Sea (where they were ineffective at stopping merchant shipping);
• had its production capabilities for just about anything (together with the residential areas of just about every major city) bombed into oblivion;
• had its last strategic offensive operation in the east (Battle of Kursk) dating August 1943, and the last strategic offensive operation in the west (Battle of the Bulge) just depleted the very last reserves Germany could muster.

At the same time Germany was running out of virtually everything, all Allies had their production capacities unthreatened by either ground or air attack (if you discount V-1 and V-2 "terror attacks" on London, which wasn't even targeted as a major production city but rather because they could not hope to hit anything smaller).

So Germany's replacement capabilities were rapidly approaching zero, while Allied replacement capabilites, if not exactly unlimited, were not limited for any practical purpose.

There was no rational way that anything Germany could do by 1945 would have swung around those odds. The Kriegsmarine was basically out of the picture, the Allies had complete air superiority over Germany (let alone their own airspace), and the Wehrmacht was really scraping the bottom of the barrel.

You know what happens if you try to divide by zero, or by infinity:

What kill ratio would Nazi Germany need in 1945 to win?

Computation error.

We would be looking at ridiculously high numbers, because Germany could no longer afford any further losses, and the Allies were better equipped than ever before.

Imagine a miracle tank that could defeat enemies 1000:1. Or a miracle jet plane that could defeat enemies 1000:1. If you have only a handful of those, your enemy can still swamp you. (As the Russians showcased pretty much throughout the war.)

By 1945 the war was lost for Germany regardless of how effective they would fight (short of summoning several thousand Iron Man suits from thin air). The German armed forces had been bled dry.

And even the highest possible kill-ratio does not give Germany any fuel...

To win the war on a strategic level (which, as I hope I have pointed out, has little to do with kill numbers) in 1945, Germany would have needed to advance back into Russia (forcing the USSR into armistice), would have needed to advance back into the Atlantic (forcing the UK into armistice), and then somehow, miraculously, do {...} to force the USA into armistice.

Because by this time, none of the Allies would have surrendered to a Germany pressed back to its own borders simply because losses soared. The Allies were so close to winning the war, strategically, that they would probably have gone to quite some lengths, losses-wise, to see it through.

A turn-around for Germany, aside from ridiculous kill numbers, would have required men, weapons, fuel, trains, planes, ships, and time that Germany just did not have anymore. And the Allies knew that perfectly well.