110 V or 230 V: which countries use which
Of the 139 countries, 22 supply 100–127 V and 116 supply 220–240 V. Of the same 139, 25 run at 60 Hz, the rest at 50 Hz.
100–127 V countries 22
Aruba, Bahamas, Barbados, Canada, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, El Salvador, Guatemala, Honduras, Jamaica, Japan, Mexico, Nicaragua, Panama, Puerto Rico, Taiwan, Trinidad and Tobago, United States, Venezuela.
60 Hz countries 25
Aruba, Bahamas, Brazil, Canada, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, El Salvador, Guatemala, Honduras, Japan, Mexico, Nicaragua, Panama, Peru, Philippines, Puerto Rico, Saudi Arabia, South Korea, Taiwan, Trinidad and Tobago, United States, Venezuela.
Does voltage matter?
The two ranges are far apart: a 230 V supply is nearly twice a 120 V one. Frequency differs too, 50 Hz in 114 of the 139 countries and 60 Hz in 25, counting Japan, which uses both.
Which of these a device accepts is printed on it. Check your device’s input rating label before using it on the other range or frequency.
The count by region and the 50/60 Hz exceptions: 230 V vs 120 V countries. Compare two countries in the adapter checker.