What is a mystery box's house edge?
Every mystery box has an expected value (EV) — the average payout if you opened it endlessly. You find it by multiplying each prize's value by its chance and adding them up. Divide the EV by the box price and you get the return-to-player (RTP): the share of your money you get back on average. The house edge is simply 1 − RTP — the operator's built-in margin.
Example: a $10 box with a 1% shot at $100, a 50% shot at $5, and a 49% shot at $1 has an EV of $3.99. That's a 39.9% RTP, a 60.1% house edge, and an expected loss of $6.01 every time you open it.
How to read your result
RTP is what you get back; house edge is what the site keeps; expected loss per open is the house edge in real money. The "over N opens" figure compounds that loss — it is the single most honest number about long-term cost. A lucky run can beat it, but the more you open, the closer your results drift toward the EV.
Why provably fair ≠ profitable
A provably-fair system proves the draw wasn't rigged — it does not change the odds or remove the house edge. A box can be 100% fair and still be poor value. Fairness is about honesty; the calculator above is about value.