Optimal tile size for GPU

A few notes about optimal tile size for rendering in Cycles

It's said to be 256 x 256

Fastest solution would be rendering with 256 x 256 tiles (according to Blender Guru[blenderguru.com])
Note that the article is 8 years old.

It's not necessarily 256 x 256

I rendered a 1024 x 1024 image in Cycles with 256 x 256 and 512 x 512 tiles and results are as follows: 0:45 and 0:42 respectively.
6.6 % faster with 512 x 512.

test is best

256 x 256 turns out to not be the golden ratio of rendering.
Best way to optimize render times via tiles is to run tests.
Render the same frame with 128 to 1024 size tiles (128, 256, 384...). Use the fastest.

[ironfistorganics]

Test is best, as every GPU is slightly different, even within the same model.

[seedee]

no, you do the test

[Pookaball]

nice, thanks