xyt556
1
I have exported the image to ENVI, how to calculate the reflectance of each band between 0-1.
ABraun
2
More information needed:
Which sensor? What data? What product level? What preprocessing was already done?
How can we know? 
xyt556
4
I have also processed level 1C product to level 2A. I want to get the reflectance between 0 -1.
ABraun
5
Level 2A is reflectance, but in Integer. To get it scaled over 0-1, you’ll have to divide by the QUANTIFICATION_VALUE from the metadata, mostly 10000