Football trading cards value is decided by supply, condition and current demand, and in football the supply question is unusually fiddly because a single photograph can appear as a dozen different cards. Getting the identification right is most of the work; the arithmetic afterwards takes a minute.
One photograph, many cards
Modern football sets issue the same image as a base card and as a ladder of parallels distinguished by border colour, foil pattern or a printed serial number. These are separate cards with separate markets. Before you search, establish which rung you are holding, because sales of the base card say nothing about the numbered version and the reverse is equally true.
The rookie premium is real and not a formula
First-year cards carry a premium over later issues of the same player, and its size varies by player and by set. You cannot compute it; you can read it, in the sold prices for each. If you are comparing a rookie to a later card, you are not comparing like with like.
Condition, and what buyers actually inspect
Corners and centring do most of the work, and on foil-fronted modern cards the surface matters more than people expect because handling shows immediately. Compare against sales in your card's condition, and be pessimistic when you judge it, because the price gap between sharp and average is wide.
Then reduce five sales to one figure
Five recent completed sales of the exact card into the card value checker. It drops the high and the low, averages the middle three and shows the spread. In football a wide spread most often means one of your five was a different parallel, which is worth checking before you accept the number.
Questions people ask about football trading cards value
Are football cards worth more than baseball cards?
Neither sport is worth more as a category. Individual cards are worth what their own supply and demand make them worth, and both sports contain cards worth thousands and cards worth cents.
What is a patch card?
A card containing a piece of material, sometimes from an item used in a game and sometimes from one manufactured for the purpose. The card's own wording distinguishes them and buyers pay very differently for each.
Does the team matter?
Only through demand, and less than people expect. Supply and condition still decide most of the outcome.
How recent should my comparables be?
A few months for an ordinary card, and weeks for anything attached to a player who is having an unusual season.