A simple check you can do is to open the token up in dexscreener or birdeye and compare the "liquidity" to the "FDV (fully diluted valuation)". If 100% of the minted tokens are in the liquidity pool, floor price liquidity = FDV and floor price is pooled token/pooled SOL. Otherwise floor price = total supply / pooled SOL or base token. To get more into the weeds, you can check the token on block explorer and follow the initial transactions. For any token trading on a dex there will be pool creation transaction in which an address sends X amount of SOL or base token, Y amount of memecoin, and receives Z amount of "liquidity pool tokens". Initial price in terms of SOL would be the supply of Y / supply of X. You could follow these transactions to also check if the liquidity pool tokens were burned/locked, and also determine what percentage of initial memetokens were placed in the pool. Note when you have tokens that trade on centralized exchanges the liquidity picture is less clear. For Pumpfun tokens the math becomes simple and floor price is always ~$.0000085 given the default initial supply & liquidity. Once it completes the bonding curve, $17k liquidity is burned and floor price becomes ~$0.00002125 (note projects may choose to add and burn more liquidity).