3.7 million bitcoins were lost due to user errors and forgotten passwords
The cryptocurrency wallet company Ledger estimates that between 2.3 and 3.7 million bitcoins may have been lost irretrievably. This figure represents between 11% and 18% of the total supply. This number includes up to one million bitcoins believed to belong to its mysterious founder "Satoshi Nakamoto" that have never been moved, in addition to other coins lost due to user errors or forgotten keys, or deliberate burns to reduce the supply.
As for Ethereum, more than 913,000 coins have been lost, equivalent to 5% of its total supply. The reason for the loss of these coins is due to user errors, deliberate burn operations (to reduce the supply), or simply because their owners forgot their passwords or access keys to their wallets.
