try it with uncooked oats or rice onto the side of a cake pan
it won't stick but you can get an idea this way
to get a guesstimate for yourself
get a thin amount in your hand as if that would be the amount that would actually stick
and just go 'round and 'round and measure how much you've used
or just go quarter way around and multiply by 4
then you can still of course 're-use' the oats/rice/quinoa