Across the world, each country have their own typical business card size. There is usually a basic standard business card dimension which is the most popular in a country.
Most of business card size should fits easily in any wallet or cardholder and legible as well.

Business Card Standard Size

If You're in the USA or Canada

The standard size is 3.5" x 2.0" (89 mm by 55 mm)

If You're in Western Europe

The standard size is 3.346" x 2.165" (85 mm by 55 mm)

If You're in Japan

The standard size is 3.582" x 2.165" (91 mm by 55 mm)

If You're in South America or Central America

The standard size is 3.543" x 1.968" (90 mm by 50 mm)

If You're in Australia or New Zealand

The standard size is 3.54" x 2.165" (90 mm by 55 mm)