SINGAPORE - Singaporeans are holding on to the world's second-most "powerful" passport, according to a worldwide ranking for passports.

Singapore was joint-second with Sweden, with a visa-free score of 156, while Germany took the top spot with one point ahead in the 2017 Passport Index.

Denmark, Finland, France, Spain, Switzerland, Norway, the United Kingdom and the United States all tied for third at 155 points.

Singapore moved up one spot from last year's index and overtook South Korea to become the highest ranked Asian passport.

The worst passports to have are from Iraq (92), Pakistan (93) and Afghanistan (94).

The index calculates each passport's visa-free score by using three steps: counting the number of countries each passport holder can visit without a visa, or where they can obtain a visa on arrival; comparing the two figures; and using the United Nations Development Programme Human Development Index (UNDP HDI) as a tie breaker.

Compiled by financial advisory firm Arton Capital, the index looks at 193 countries and six territories.

Another global passport ranking last year placed Singapore fifth, while Germany was also in first place.

The Henley & Partners Visa Restrictions Index 2016 ranked passports according to the total number of other countries citizens have visa-free travel to.

The index was produced with the International Air Transport Association (IATA).