The survey of 2,000 is part of a recruitment campaign highlighting how young people wile away a day a week.
The Army Reserve said many young people think joining the reservists is too much of a time commitment - despite saying they would like to learn a new skill if they had more time.
The Army is aiming to reach a target of 30,000 trained reservists by 2019.
Reservists are required to commit to at least 19 days a year.
The study carried out on behalf of The Army Reserve by research specialists Opinion Matters asked 2,021 people, aged between 18 and 35, about their personal lives.
It found that more than 60% (1,213) said they would be interested in learning a new skill if they had more spare time, and a fifth (404) would like to volunteer and help others.
A spokesman for the Army Reserve said the research was designed "to get people who may have not considered the Army to think again about being a reservist and realise that it's not a huge commitment".
"With a time commitment from just 19 days a year, much of which is made up of short training evenings during the week, it's a realistic option for a lot of people and that the rewards are huge," he added.