Question:How many fighting men did Joab count in Israel and Judah? II Samuel 24:9 says 800,000 and 500,000; but I Chronicles 21:5 says 1,100,000 and 470,000.
When dealing with numbers, you must ask yourself two questions: Are the same group of people being counted and could one account or the other be rounding the answer? We do it all the time. I am in Cullman, Alabama, today and someone ask how far is it from Omaha. Do I answer the direct distance, the number of miles if you drove the shortest route, or the number of miles I actually drove because we stayed overnight with my brother? Should I give the answer to the tenth of a mile, to the nearest mile or just round it to the nearest hundred miles? All the possible answers are different, yet all of them are correct.
"Then Joab gave the sum of the number of the people to the king. And there were in Israel eight hundred thousand valiant men who drew the sword, and the men of Judah were five hundred thousand men" (II Samuel 24:9).
"Then Joab gave the sum of the number of the people to David. All Israel had one million one hundred thousand men who drew the sword, and Judah had four hundred and seventy thousand men who drew the sword. But he did not count Levi and Benjamin among them, for the king's word was abominable to Joab" (I Chronicles 21:5-6).
While subtle, there are differences between what is being counted. I Chronicles says all Israel, but II Samuel just says Israel.
The difference is 300,000. In I Chronicles 27:1, we learn that the standing army consisted of 12 divisions of 24,000 men. That comes to 288,000 men. Later in I Chroincles we learn that there were officers for each tribe's leader. The number isn't given, but if we assume that these units had about 1,000 men, then the total standing militia was about 300,000 men. Therefore, the most logical conclusion is that II Samuel 24 didn't include the already active military, while I Chronicles 25 added them in because the number included all in Israel.
The difference between Judah's two numbers is 30,000. We do know that there were 30,000 men assigned to patrol the Philistine boarder (II Samuel 6:1). We do note that I Chronicles 21:5 doesn't say all of Judah like it did with Israel. So it is possible the border patrol was not included. Another possibility is to remember that a plague came in response to the numbering, that killed 70,000 men (II Samuel 24:15). One account may be giving pre-plague numbers and the other post-plague numbers. But more likely the author of II Samuel 24:5 simply rounded his numbers to the nearest 100,000 and 470,000 rounded is 500,000.
While we can't say wih absolute certainty which reason is correct for the two sets of numbers, the fact that there are several reasonable explanations means there is no need to conclude that there is a conflict between the two records.