Arithmetic on today's supply, not a forecast. It assumes nothing about whether Bitcoin could attract that much money.
A coin's market capitalisation is its price multiplied by the number of coins in circulation. Bitcoin has 20,074,644 BTC in circulation at $79,954.73 each, which is $1.61T. Holding that supply still and putting Ethereum's $281.18B in its place gives $14,006.94 per BTC.
Bitcoin is already worth more than Ethereum. Moving to the smaller cap would take BTC down to $14,006.94, which is 0.175x of what it trades at now.
Supply is held still, and in practice it moves: coins are minted, burned and unlocked, and every one of those changes the price a given market capitalisation implies. The figure also says nothing about whether the money exists to buy BTC at that level, which is the part that actually decides a price.
$14,006.94 per BTC. That is Ethereum's current market capitalisation of $281.18B divided across the 20,074,644 BTC in circulation.
0.175x. Bitcoin trades at $79,954.73 today and Ethereum's market cap is $281.18B against Bitcoin's $1.61T.
No. It is one division: Ethereum's market capitalisation spread over the supply of BTC that exists today. It assumes nothing about whether Bitcoin could attract that much money, and it holds the supply still when in practice supply changes.
It sets it. Market cap is price times circulating supply, so the same $281.18B of market cap spread over more coins gives a lower price per coin. This uses the 20,074,644 BTC in circulation now.