915 days minimum...

[auditorpnine]

read somewhere, a *new GC holder must spend at least 915 days on usa soil, in the subsequent consecutive 5 year period,
to be *eligible for citizenship (not a given, though)

is it at least 183 days *every year on usa soil
or
total 915 days in 5 years - but no *single out of usa stay to be more than 180 days.

now, just for argument-
can i stay outside usa:
total 245 days 1st year (no *single stay 180+ days), 110 days 2nd year, 210 days 3rd year, 38 days 4th year... (total on usa soil will be 915+ days)
(assuming, they do not revoke my GC status for my frequent trips - do/will they ?)

[Enub4]

https://www.uscis.govhttps://www.imm...on-information

This page say

• Show that you have been physically present in the United States for at least 30 months out of the 5 years immediately preceding the date of filing Form N-400.

[scientist2016]

read somewhere, a *new GC holder must spend at least 915 days on usa soil, in the subsequent consecutive 5 year period,
to be *eligible for citizenship (not a given, though)

is it at least 183 days *every year on usa soil
or
total 915 days in 5 years - but no *single out of usa stay to be more than 180 days.

now, just for argument-
can i stay outside usa:
total 245 days 1st year (no *single stay 180+ days), 110 days 2nd year, 210 days 3rd year, 38 days 4th year... (total on usa soil will be 915+ days)
(assuming, they do not revoke my GC status for my frequent trips - do/will they ?)

The numbers are a guidance. The interviewing officer has the discretion to judge whether you pass the bar required to establish that you indeed were a "permanent resident". People have tried the kind of arithmetic you mentioned, and the results vary depending on individual circumstances and the judgement of the interviewing officer.