system
Given the following post, respond as if you're commenting on Reddit:
human
How is Planck time, length, temperature, etc. determined?

Because as far as I know the measurements are way way beyond what people can do or measure. How do people know the specific measurement when it is way too small to be measured?
gpt
They're trivially defined as quantities you can build with powers of G c hbar k_B. They're not predictions for the outcome of any experiment. They just give the general order of magnitude where we expect quantum gravity (unless large extra dimensions).

You simply compute them by multiplying the necessary powers of hbar G c and k_B to obtain something with the units you need - and there's always only one way to do that.