When it comes to pricing their delicacies by size, Chinese bakeries could be said by customers "to be taking the cake".

In most bakeries, cakes are only labeled with their diameter measured in cun, which most people think is a Chinese unit of 3.33 centimeters. However, to bakeries it stands for the much shorter "inch" (2.54 cm), or ying cun.

And it makes a big difference when buying cakes. If the cun means inch, a 10-cun cake is 506 square centimeters. If it's the Chinese measure, the cake is a tasty 870 sq cm.

"It's confusing. Why can't they write down the exact size, rather than simply put an abbreviation there?" said Zhang Huijie, a white-collar worker in Shanghai, with a sweet tooth.

"In fact, it's difficult for ordinary people to calculate the size of the cake using either of the measurement units. I buy cakes often and I have no idea of the exact size of them," she said, adding that she usually tells shop assistants how many people will share the cake and lets them judge.

In Shanghai, almost all of the bakeries sell cakes by diameter-inch, labeled as cun.

At Ruby Bakery, a popular local chain, the diameter of an 8-cun cake is about 20 cm.

Over at the Japanese-flavored Ichido, a 6-cun cake from its outlet on Huaihai Zhonglu, at nearly 17 cm in diameter, is neither one nor the other, but somewhere between the two cuns.

"Using inches can be regarded as a convention in the industry," said Cao Xiuhong, who heads Ichido's customer service department.

"In fact, few customers ask about the exact diameter. Most of them tell us the number of people who are going to share the cake," she said.

Zhao Jiaoli, secretary-general of the Shanghai Commission of Consumers' Rights and Interests Protection, said that if using inches is the convention in the industry, bakeries are not at fault.

"However, they have an obligation to tell customers what the measuring units mean. They shouldn't use a vague word that may be misleading," she said.

But the confusion over cun or inch will be clarified soon. According to new regulations on the labeling of prepackaged food, issued by the Ministry of Health, solid foods should be measured by weight. The regulations will take effect from April 20.

In Ichido's outlets, the weight of cakes is only given in the catalog, which is offered to customers upon request.

"We will improve the labeling in accordance with the new regulations soon," Cao said.

Song Jianing, deputy chief editor of the consumer affairs channel at a major local website, online.sh.cn, said: "It is not enough to describe a three-dimensional cake only by the area of its surface. The best way is to label both the weight and diameter.

"Although many customers don't pay much attention to the weight, bakeries should still obey the relevant regulations."

yangyijun@chinadaily.com.cn