It's a measure of how well your diet is working, but it can be inconvenient to check if your waist is shrinking by wrapping a tape around it and reading off the number.

Six college students say a device they have developed does the cumbersome work for you, sending a reading to a cellphone and doing away with the need for a conventional measuring tape.

The device was put on display on Saturday and Sunday during Maker Faire Tokyo 2015 at Tokyo Big Sight, the nation's largest convention center, in the capital's Odaiba district.

"We hear from our friends who graduated and started working that they tend to gain weight because they often drink after work," said Yuki Matsuda, a 22-year-old student at Nara Institute of Science and Technology, as he showed off the belt Sunday.

The team also includes students from National Institute of Technology Akashi College, Kagawa University and Hokkaido University.

Matsuda said they wanted to come up with ideas to help people in this situation.

The belt, equipped with a sensor, calculates the size of a person's waist by registering how much of the belt has been inserted through a buckle. It uses a sensor like that in a computer mouse, which measures movement.

Data generated by the module is sent to a smartphone, which calculates the waist size with the use of a special app.

Matsuda said the belt can also indicate by how much a user's belly has bloated following a meal.

The team hopes to secure investment by crowdfunding this year, he said.

Maker Faire showcases gadgets and technologies developed by individuals and corporate manufacturers.