Upvote:11
TL;DR version: Between 442 462 and 1 245 450 people in all countries of the Eastern Front.
Long version
Warning: I believe a bad estimate is better than no estimate at all and I'm aware of the flaws of this "method". If you know a better one, I'm all ears. Maybe you can take these calculations and improve them.
Miriam Gebhardt writes in her book Als die Soldaten kamen: Die Vergewaltigung deutscher Frauen am Ende des Zweiten Weltkrieges (German, "When the soldiers came: Rapes of German women at the end of World War II) that
We can estimate the number of rapes per soldier. The author of that book writes that the maximum number of troops stationed in Germany was, at its peak,
No data is available in the book for the French and Belgians. The data for the Soviets (1 500 000 in 1945, 800 000 in 1949) is available, but looks suspicious to me (reason see below).
From these data we can calculate the estimate of rapes per soldier:
For the Soviets that estimate would be an order of estimate lower, which doesn't look believable to me.
If we assume that the Germans in the Soviet Union raped with roughly the same intensity as the Americans and the British in Germany, we can get an estimate by multiplying rapes per soldier by the strength of the German troops in the Soviet Union. This assumption can be justified by the claim that ideas about sexual violence at war used by the Nazis and the Allies were similar: Regina Mühlhäuser writes in her paper Eine Frage der Ehre. Anmerkungen zur Sexualität deutscher Soldaten während des Zweiten Weltkriegs (German; "A question of honor // Notes about the sexuality of German soldiers during World War II"):
In the middle of the 20th century Göring's argumentation was in accordance with the values and norms system in Europe and the USA.
[...]
In 1946 [acts of sexual violence] were considered by the Allies not as a crime to be punished, but as a natural side effect of the war.
According to Wikipedia there were 3 933 000 German troops on the Eastern Front.
This results in following estimates of German rapes in the Soviet Union, Poland, Czechoslovakia, Yougslavia (and other German adversaries on the Eastern Front):
For comparison: According to Miriam Gebhardt, 860 000 German women were raped between 1945 and 1955 in all Germany (Eastern and Western), by all occupational powers.