In terms of their basic card stock dimensions, Pokemon cards and most modern baseball cards are generally the same standard size. The vast majority of Pokemon cards as well as baseball cards printed since the 1990s measure about 2.5 inches tall by 3.5 inches wide. This has become the de facto standardized size for trading cards in general over the past few decades.
There are some key differences in the dimensions beyond just the basic card stock size that are worth noting. One difference is that Pokemon cards usually have significantly thicker card stock than standard baseball cards. Pokemon cards are printed on thicker, higher quality card stock that is sturdier and less prone to bends, creases or damage compared to baseball cards. This thicker card stock contributes to Pokemon cards feeling more substantial in the hand.
The next difference relates to the dimensions of the actual illustrated artwork and information area contained within the borders of the cards. On Pokemon cards, the illustrated image takes up almost the entire visible front face area of the card from top to bottom and side to side, leaving only a thin border around the edges. On baseball cards the illustrated player image is generally centered somewhat higher on the front face with blank space below and sometimes blank space on the sides as well inside the borders. This means the actual illustrated area of a Pokemon card is almost always larger relative to the overall card size compared to most baseball cards.
Perhaps the biggest difference in dimensions comes from standard game-related features added to the fronts and backs of Pokemon cards versus baseball cards. Pokemon cards are printed with a large extra box or banner at the bottom of the face for displaying important game stats and attributes like attacks, hit points/health, and weaknesses/resistances associated with that Pokemon character. This large stat/game text box takes up significant extra vertical space, increasing the total height of the illustrated portion of Pokemon cards by close to half an inch on average compared to baseball cards.
The reverse sides or backs of Pokemon cards contain equally large boxes and banners for more detailed game text, abilities, and history relating to that specific Pokemon character. Baseball cards on the other hand normally have little game or player related text or images on their reverse sides beyond basic identification data which takes up far less space. So in total, Pokemon cards with their graphics and game details extending across both sides end up with dimensions closer to 3 inches tall by 4 inches wide on average to accommodate everything.
Aside from basic physical dimensions, there are also differences in card templates and framing depending on the specific Pokemon card set versus baseball card brand and year printed. Some Pokemon league promo cards like from GameStop promotions stray from the norm being thicker and noticeably taller. And vintage baseball cards prior to the 1990s were manufactured in all sorts of variable non-standard sizes as the industry evolved. But taking a broad view, the dimensional attributes described like card stock thickness, illustration sizes, and extra game text all contribute to Pokemon cards having distinctly larger footprints overall compared to standard size baseball cards in common circulation today despite their technical 2.5×3.5 inch dimensions.
While Pokemon cards and modern baseball cards share the same nominal 2.5×3.5 inch basic card stock size, there are considerable differences in card thickness, illustration areas, additional game text dimensions, and templates that result in Pokemon cards usually having noticeably larger total physical dimensions compared to standard baseball cards. The extra features and details printed on Pokemon cards necessitate their slightly larger scale to adequately display the associated art, lore and game mechanics encompassed in each collectible card.
