Using 9/11s as our reference, since Americans of my age can fully recall the magnitude of what that meant. And after October 7, it was a comparison mentioned frequently in the press.
In 9/11, 2,977 people were killed. America's population at the time was around 290 Million people. So the ratio of Americans to those killed was 96,500, or around 100,000 Americans for each person who was killed. Let's use 100,000 for general comparison purposes.
October 7th killed 1,200 according to the US Department of State. Israel's population is around 9.5 million. The ration of Israelis to those killed was 7,916. Let's say 8,000 Israelis for each person who was killed. Compared to 9/11, by this measure, it was 12.5 times worse. It was like 12.5 9/11s.
Since the Israeli offensive began, 40,000+ Palestinians have died in Gaza. The population of Gaza is around 780,000. The ration of Gazans to those killed is 19.5. I'll round it to 20 Palestinians for each person who was killed. Compared to 9/11, by this measure, it was 5,000 times worse. Compared to the October 7th, it was 400 times worse. If even half of those were combatants (most likely way less than half were actually combatants), it was still 2,500 9/11s or 200 October 7th's.
The numbers are close enough. They're just numbers. There are other factors that are important.
American Civil War: Population of America vs Casualties: 31,000,000 / 620,000 casualties is 50.