From Memory.
Germany drafted about half of the population into the active army for two years, so we are talking about 1 man year out of the average man's life. Germany had about 1.8 million births per year, so 0.9 million men, which is about the size of there standing army. (0.8 million army, 0.1 million navy)
France drafted about 87% for 3 giving you 2.61 years average service. I don't have the births per year, but France had 40 million to Germany 65 million and this implies 0.45 million men per year and an army of 1.17 million. I think it was closer to 0.9 Army and 0.1 Navy. There error here is probably a combination of some of the following.
-Navy
-Other government jobs that count in lieu of military service.
-The 87% is a wee bit high.
-There service was a bit under 3 years. They either don't count men in basic training/MOS schools or they let some out a little early.
BTW, if you are curious what happens if their is no WW1 and Germany does not find better relations with Russia/France by 1917, this shows the likely solution. Germany has to have a bigger army which it both has the men for and the GDP, but would cause massive problems for the Reichstag. Also, France probably drops back to a 600K army, which will cause many difficult issues for them since many of their troops have to be stationed in the Empire.