There is only a 1mm difference between the threads of E26 and E27 so they are mostly identical, but it's important to purchase the correct bulb certified for use in your country.

An easy reference of what Bulb is recommended for major markets is as follows:

• United States & Canada - E26
• Central & South America* - E26
• Caribbean Islands - E26
• Japan & Taiwan - E26
• Rest of the world - E27
• * - Brazil - E27

If you'd like to know precisely which bulb each country uses, here is a complete list.

The following countries use E26 bulbs:

• Anguilla
• Aruba
• Bahamas
• Barbados
• Belize
• Bermuda
• Canada
• Canada
• Cayman Islands
• Colombia
• Costa Rica
• Cuba
• Dominican Republic
• Ecuador
• El Salvador
• Guatemala
• Haiti
• Honduras
• Jamaica
• Japan
• Libyan Arab Jamahiriya
• Mexico
• Nicaragua
• Panama
• Taiwan
• Trinidad and Tobago
• United States
• Venezuela
• Virgin Islands, British

The following countries use E27 bulbs:

• Afghanistan
• Aland Islands
• Albania
• Algeria
• Andorra
• Angola
• Antigua And Barbuda
• Argentina
• Armenia
• Australia
• Australia
• Austria
• Azerbaijan
• Bahrain
• Bangladesh
• Belarus
• Belgium
• Benin
• Bhutan
• Bolivia
• Bosnia And Herzegovina
• Botswana
• Bouvet Island
• Brazil
• British Indian Ocean Territory
• Brunei
• Bulgaria
• Burkina Faso
• Burma
• Burundi
• Cambodia
• Cameroon
• Cape Verde
• Central African Republic
• Chad
• Chile
• China
• Christmas Island
• Cocos (Keeling) Islands
• Comoros
• Congo
• Congo, The Democratic Republic Of The
• Cook Islands
• Côte d'Ivoire
• Croatia
• Cyprus
• Czech Republic
• Denmark
• Djibouti
• Dominica
• Egypt
• Equatorial Guinea
• Eritrea
• Estonia
• Ethiopia
• Falkland Islands (Malvinas)
• Faroe Islands
• Fiji
• Finland
• France
• French Guiana
• French Polynesia
• French Southern Territories
• Gabon
• Gambia
• Georgia
• Germany
• Germany
• Ghana
• Gibraltar
• Greece
• Greenland
• Grenada
• Guadeloupe
• Guernsey
• Guinea
• Guinea Bissau
• Guyana
• Heard Island And Mcdonald Islands
• Holy See (Vatican City State)
• Hong Kong
• Hungary
• Iceland
• India
• Indonesia
• Iran, Islamic Republic Of
• Iraq
• Ireland
• Isle Of Man
• Israel
• Italy
• Jersey
• Jordan
• Kazakhstan
• Kenya
• Kiribati
• Korea, Democratic People's Republic Of
• Kosovo
• Kuwait
• Kyrgyzstan
• Lao People's Democratic Republic
• Latvia
• Lebanon
• Lesotho
• Liberia
• Liechtenstein
• Lithuania
• Luxembourg
• Macao
• Macedonia, The Republic Of
• Madagascar
• Malawi
• Malaysia
• Maldives
• Mali
• Malta
• Martinique
• Mauritania
• Mauritius
• Mayotte
• Moldova, Republic of
• Monaco
• Mongolia
• Montenegro
• Montserrat
• Morocco
• Mozambique
• Myanmar
• Namibia
• Nauru
• Nepal
• Netherlands
• Netherlands Antilles
• New Caledonia
• New Zealand
• Niger
• Nigeria
• Niue
• Norfolk Island
• Norway
• Oman
• Pakistan
• Palestinian Territory, Occupied
• Papua New Guinea
• Paraguay
• Peru
• Philippines
• Pitcairn
• Poland
• Portugal
• Qatar
• Reunion
• Romania
• Russia
• Rwanda
• Saint Barthélemy
• Saint Helena
• Saint Kitts And Nevis
• Saint Lucia
• Saint Martin
• Saint Pierre And Miquelon
• Samoa
• San Marino
• Sao Tome And Principe
• Saudi Arabia
• Senegal
• Serbia
• Seychelles
• Sierra Leone
• Singapore
• Slovakia
• Slovenia
• Solomon Islands
• Somalia
• South Africa
• South Georgia And The South Sandwich Islands
• South Korea
• Spain
• Sri Lanka
• St. Vincent
• Sudan
• Suriname
• Svalbard And Jan Mayen
• Swaziland
• Sweden
• Switzerland
• Syria
• Tajikistan
• Tanzania, United Republic Of
• Thailand
• Timor Leste
• Togo
• Tokelau
• Tonga
• Tunisia
• Turkey
• Turkmenistan
• Turks And Caicos Islands
• Tuvalu
• Uganda
• Ukraine
• United Arab Emirates
• United Kingdom
• United Kingdom
• United States
• United States Minor Outlying Islands
• Uruguay
• Uzbekistan
• Vanuatu
• Vietnam
• Wallis And Futuna
• Western Sahara
• Yemen
• Zambia
• Zimbabwe