The weight of 100 baseball cards can vary depending on several factors like the size, thickness, and material of the individual cards. We can make some reasonable estimates and assumptions to come up with an average weight.

Most standard modern baseball cards are made from a paper or cardboard stock that is thin but durable enough to withstand repeated handling. The standard size of baseball cards is 2.5 inches wide by 3.5 inches tall, which is known as the standard “bubblegum card” dimensions that were popularized beginning in the late 1880s. Over time card sizes have varied slightly, with some vintage cards being a bit smaller and some specialty or commemorative cards being slightly larger.

For the purposes of this estimate, let’s assume all 100 cards are standard modern size bubblegum cards. The thickness of modern stock tends to be relatively consistent, measuring around 0.009 to 0.011 inches thick on average. Baseball cards prior to the 1970s tended to be a bit thicker at around 0.014 to 0.018 inches, while more modern rare and premium cards released since the 1990s can be as thin as 0.007 to 0.009 inches thick.

To calculate the total weight, we first need to determine the weight of an individual card. If we take the average dimensions of a standard modern card being 2.5 inches by 3.5 inches with an average thickness of 0.01 inches, we can use the formula of multiplying length x width x thickness x density to find the volume and then mass. The density of standard paper/cardboard used for cards is typically around 0.6 grams per cubic centimeter. Plugging the dimensions into the formula gives us a volume of about 0.0875 cubic centimeters for a single card. Multiplying that volume by the density of 0.6 grams/cc tells us each card weighs approximately 0.0525 grams or 52.5 milligrams.

Now that we know the average weight of a single card, calculating the total weight for 100 cards is simply a matter of multiplying. If each card weighs 0.0525 grams, then 100 cards would weigh 100 x 0.0525 grams, which works out to be approximately 5.25 grams or 1.85 ounces.

Based on making reasonable assumptions about the average size, thickness, and material composition of a standard modern baseball card, we can estimate that 100 such baseball cards placed on a scale would register a total weight of around 5.25 grams or 1.85 ounces. Of course, this number could vary slightly higher or lower depending on the exact card stock and quality variations within the sample of 100 cards. But overall, this should provide a fairly accurate ballpark figure for the total weight of a typical random group of 100 modern baseball cards.

There are a few additional factors that could cause the weight to vary some from this estimated average. If the sample consisted of older vintage cards from the pre-1970s era that tended to be thicker, the total weight would likely be a bit higher at perhaps 6-7 grams for 100 cards. Conversely, if the sample contained specialty or premium cardboard stock cards from recent years that use lighter weight materials, the total might be lower at maybe 4-5 grams. Card size could also play a minor role, with slightly oversized or undersized cards weighing proportionally more or less. Overall though, under most normal circumstances of mixing card vintages and sizes, 5.25 grams represents a reasonable mean estimate for the total average weight of 100 standard modern baseball cards.