Assumptions:
The civilian death rate is proportional to the population in the area of conflict.
The civilian death rate is inversely proportional to the size of the area of conflict.
Therefore, the civilian death rate is proportional to the population density of the area of conflict.
Siege of Mariupol:
Initial population: 425,681
Area: 244 km
2 Estimated civilian deaths, per defender: 25,000+
Duration: 86 days
Behavior of defender:
- Distinguished themselves from civilians.
- Attempted to separate themselves from civilians.
- Tried to protect and evacuate their own civilian population.
- Generally-speaking obeyed the laws of war.
Civilian death rate: 290+ per day
Civilian death rate divided by population density: 0.17+ per day
War in Gaza:
Initial population: 2,375,259
Area: 365 km
2 Estimated civilian deaths, per defender: 28,473+
Duration as of February 13th: 130 days
Behavior of defender:
- Intentionally doesn't try to distinguish themselves from civilians.
- Intentionally doesn't try to separate themselves from civilians.
- Intentionally takes human shields.
- Intentionally commits perfidy.
- Intentionally tries to maximize their own civilian casualties.
- Generally-speaking has complete and utter disregard for the laws of war.
Civilian death rate as of February 13th: 220+ per day
Civilian death rate as of February 13th divided by population density: 0.034+ per day
Conclusion: As of February 13th, notwithstanding the behavior of the defenders, the adjusted civilian death rate of the War in Gaza is approximately 20% of the adjusted civilian death rate of the Siege of Mariupol. If Israel was as indiscriminate as Russia was in Mariupol, the nominal civilian death rate would have to be about five times as high, i.e. 1100+ per day.
Assuming that the civilian death rate is proportional to the "recklessness" of the defender, then adjusting for recklessness would make the civilian death rate in Gaza to be even higher than 1100+ per day if Israel was as indiscriminate as Russia in Mariupol. However, recklessness is not something that is easily measured with numbers.