What is sleep efficiency if total sleep is 330min and total time in bed is 400 min

You can calculate your sleep efficiency by dividing the time you're asleep by the total time in bed. So, if you sleep for six out of eight hours in bed, your sleep efficiency is 75%. What's a good score? Anything 85% or higher is considered “normal.”

Explanation:

Efficiency is often measured as the ratio of useful output to total input, which can be expressed with the mathematical formula r=P/C, where P is the amount of useful output ("product") produced per the amount C ("cost") of resources consumed.