CS2 Case Opening RTP and House Edge: How to Do the Math Yourself

Expected value, or EV, is the average return of one case opening if you could repeat it endlessly. You calculate it by multiplying each item's value by its drop chance and adding the results. A case that costs $10 with an EV of $9 returns $9 per opening on average over the long run, even though no single opening ever pays exactly that.

RTP, return to player, is the same idea expressed as a percentage of the price: EV divided by case price. The $10 case with a $9 EV has a 90% RTP.

House edge is what remains: 100% minus RTP. It is the site's average margin per opening, and it is how a case site pays for skin inventory, payment processing, support, and rewards. The three numbers are one fact viewed three ways. If you know any one of them plus the case price, you can derive the other two.

The formula is simple: EV equals the sum of (item value x drop chance) across every item in the case. Then RTP = EV / case price, and house edge = 100% - RTP. The hard part is not the arithmetic, it is getting honest inputs.

You need two things per item: its value and its drop probability. On CaseRush, every active case publishes both on a public odds page, linked from the case itself, showing the full item list with drop chances against the case price. Each item is assigned a ticket range out of 10,000 total tickets and one ticket is drawn per opening, so the listed percentages map directly to concrete odds. The page also computes the price, expected value, RTP, and house edge for you, and shows how the margin splits between platform share and creator royalty, the royalty applying to community-made cases.

Most sites do not publish this. If a site shows you the item pool but not the probabilities, you cannot compute EV, and you are taking the value of the case entirely on faith.

Here is the math run on 1% Club, an official CaseRush case, using its public odds page as of early July 2026. One thing to know first: the odds page lists the case price and every item value in coins, the site's balance currency, not in dollars. Because the price and the item values share the same unit, the unit cancels out of the RTP math entirely; the ratio is what matters. The case costs 6.07 coins and contains six items. Multiply each item's value by its drop chance:

Adding those up gives an EV of about 5.46 coins. RTP is 5.46 / 6.07, roughly 89.9%, which leaves a house edge of about 10.1%. That matches the figures the odds page displays at the top, so you can always check your own arithmetic against the page.

Notice the shape behind the average. The four premium items add up to exactly 1% combined, which is where the case gets its name. The other 99% of openings return 2.12 coins or less on a 6.07-coin case. RTP describes the long-run average, not the typical result: two cases with identical RTP can feel completely different to open depending on how the value is distributed.

One caveat: item values move with the skin market, so the exact figures on any odds page drift over time. Treat the numbers above as a snapshot and check the live page before you open.

Because most case sites do not publish drop tables, industry-wide RTP figures are estimates, mostly from affiliate and review sites rather than audited data. Treat them as rough ranges, not verified facts.

With that caveat stated: review sites commonly place case-opening RTP somewhere around 65% to 81% as a category, against roughly 95% for typical online slots and about 99.5% for well-played blackjack. Crash-style games are usually cited at around a 1% to 4% house edge. In other words, case opening tends to sit at the expensive end of chance-based games, which makes checking the specific case you are about to open more important, not less.

This is also why per-case transparency matters more than category averages. A published drop table replaces the estimate with arithmetic. You do not have to guess where a case falls in that 65-81% range; you can compute it, or read the RTP straight off the odds page.

Provably fair is about integrity. It lets you verify that a result came from a server seed committed before you played, combined with your client seed and a nonce, and was not changed after the fact. On CaseRush you can check your seed status and verify past results on the provably fair page.

RTP is about value. It tells you what the game returns on average. A case can be perfectly provably fair and still have a low RTP; the site would simply be running a game with poor odds, honestly. A fair outcome and generous odds are separate questions, and neither one implies the other.

So check both. Provable fairness answers 'was this outcome manipulated?' The odds page answers 'what is this case actually worth?' A site worth using gives you the tools to answer each question yourself instead of asking you to trust either one.

Every case with a house edge has an EV below its price, on this site and every other. The average outcome of opening cases is a loss, by design, exactly like any casino-style game. A higher RTP means you lose less on average over time. It never means you win, and no case is beatable through volume or timing.

EV also says nothing about your next opening. Variance dominates short runs: you can hit a 0.25% item on your first case or open two hundred without seeing it, and neither streak changes the underlying probabilities.

Treat case opening as paid entertainment with a known average cost. Decide what you are comfortable spending before you start, do not open cases to win back losses since the math is identical after a losing streak, and stop when it stops being fun. If it no longer feels like a choice, take a break.