Random Trivia: The only countries left on the planet - besides the United States of America - that have NOT converted to the metric system are Liberia and Burma.
For all foreign passports photos in all other countries, the size is measured in millimeters. European passport photos are almost (I said "almost") all uniformly the same size - 35x45mm.
Most all drug stores that still offer passport photos are only set up to create passports that conform to US standards (2x2 inches). Ask them for a 35x45 millimeter image and they're likely to send you back to square one (Google). Fortunately, the Walgreens and the AAA office here in Carrollwood have a backup plan - Newsome's Studio of Photography, located at 10012 N. Dale Mabry Hwy in Tampa (Cypress Point Office Park).
Newsome's Studio provides residents from all over the Tampa area with high quality passports, citizenship, immigration, DV Lottery, and visa photos for US as well as any foreign country on the planet, in less than ten minutes!