In the datasheet that you can download from the ST.com site you will find:
2.10.4 ALS count to lux conversion
Which unfortunately does not copy onto this answer very well.
But go to www.st.com, search for VL6180X and the download of the datasheet will be straight forward.
In order to give better visibility on the answered topics, please click on 'Accept as Solution' on the reply which solved your issue or answered your question. It helps the next guy.
