CS2 Case Odds Calculator: Drop Chances and Opening Costs

How to use the CS2 Case Odds Calculator

1. Define the target: a rarity category and a specific skin are different outcomes.
2. Enter a justified per-opening probability for that target. Use 0 if it cannot drop from the selected case.
3. Enter the number of openings and both costs in the same currency.
4. Calculate and read the probability of no target drops alongside the probability of at least one.

Prices are entered manually. The tool does not connect to a marketplace, include sale proceeds, apply withdrawal fees or estimate expected resale value. If you are comparing costs in different currencies, convert them consistently before entering the figures.

The probability formula

For chance p written as a decimal and n independent openings, the probability of at least one target is 1 − (1 − p)ⁿ. The probability of zero targets is (1 − p)ⁿ, and expected target drops equal n × p. “Expected” is an average over repeated groups, not a guaranteed result for your group.

At an illustrative 0.26% rate, 100 attempts give approximately 22.9209% for at least one target and 77.0791% for none. The expected count is 0.26; it does not mean you receive part of an item. At a hypothetical case price of 0.51 and key price of 2.49, those attempts cost 300 in the entered currency.

Rare items versus exact knives, gloves and patterns

A category probability cannot be used as the probability of an exact item in that category. A particular model, finish, condition and seed is narrower. Do not multiply assumed equal probabilities for these attributes without evidence that the assumptions hold. This tool accepts your target rate; it does not infer an undocumented item-generation distribution.

For the full explanation of rarity categories and limitations, read CS2 case odds explained. For the effect of a finish's layout and wear, use CS2 skin patterns explained. Compare direct-purchase routes through our skin marketplaces guide.

Compare scenarios with the CS2 case odds calculator

Use the CS2 case odds calculator with a defined spending limit, then compare several opening counts without changing the target definition. A larger number raises the group's total cost and cumulative chance together. It does not make any particular opening more likely to succeed under the independent model.

Keep a record of the entered rate and where it came from. If a published figure describes all rare special items, label your result with that category rather than the name of one knife. Change only one assumption at a time when comparing scenarios, so you can see whether the difference came from probability, price or opening count.

The CS2 case odds calculator is also useful for showing the chance of finishing with no target drops. Read that figure alongside total expenditure before drawing a conclusion. Compare direct purchase prices separately through the Steam Community Market; market purchases and random openings answer different questions.

Compare two CS2 case odds calculator scenarios

To isolate the effect of opening count, use a hypothetical target chance of 1% and a combined case-and-key cost of 3 per opening. Ten independent openings cost 30. Under that model, the chance of no target drops is 0.99 to the power of 10, approximately 90.4382%, leaving about 9.5618% for at least one target drop.

Keeping the same rate and increasing the count to 100 raises the cost to 300. The chance of no target drops becomes approximately 36.6032%, and the chance of at least one becomes approximately 63.3968%. The next opening still has a 1% target chance in both scenarios. These invented inputs illustrate the formula and do not describe a particular container.

Expected count is different from success probability

At that 1% rate, the expected target count for 100 openings is one. That does not mean exactly one target must appear, and it does not mean the chance of at least one is 100%. A group can contain zero, one or several targets. The expectation is an average across repeated groups under the stated assumptions.

Use the CS2 case odds calculator to keep these outputs separate. Read the expected count, the chance of no targets and the total expenditure together. They describe different aspects of the same model and should not be substituted for one another in a comparison.

Check the extreme inputs

A target chance of zero represents an impossible target under the entered model, so increasing the opening count cannot produce it. A target chance of 100% represents a certain target on each modelled opening, while zero openings still means zero expenditure and zero target drops. These checks help you understand what the fields mean before entering a real scenario.

If your target or source probability changes, start a new comparison. Do not mix a rarity-category rate from one container with an exact-item description from another. Keep every cost in the same currency and record which numbers are examples rather than current quotations.

Frequently asked questions

Does opening more cases improve the next opening?

No, under this model every opening has the same entered chance. The cumulative probability across a larger group changes, while the next opening's probability remains p.

Does 1 in 385 mean a guaranteed drop by opening 385?

No. An average reciprocal rate is not a deadline or pity counter. A sequence can finish without the target.

Does the result show expected profit?

No. The calculator totals expenditure and counts target outcomes. Profit would require a complete item-value distribution, current realisable prices and applicable costs.

Can I enter a custom probability?

Yes, from 0% through 100%. Enter percentages, so 0.26 means 0.26%, not 26%. The number of openings must be a whole number.

Are case and key prices current?

No. They are editable examples. Enter the actual prices you want to model in the same currency.