Odds
Every hash is a ticket, but the raffle is enormous
Bitcoin lottery mining is simple to understand and hard to emotionally accept. A tiny miner can find a block, but the average wait can be thousands of years.
The rough formula
The probability per hash is approximately one divided by difficulty times 2^32. More hashrate means more attempts. Higher difficulty means a harder target.
Expected time is not a schedule. A miner can get lucky early, or never find a block at all.
Why the calculator matters
The calculator turns a tempting hashrate number into daily, monthly, and yearly odds. That keeps upgrades grounded in reality.