What formula does this calculator use?

It uses the binomial complement: P = 1 − (1 − p)^n. This gives the probability of at least one success in n independent trials each with probability p. It is the standard and correct formula for this scenario.

What does "at least one drop" mean?

It means the probability that you get the item one or more times across all your attempts. It is not a guarantee unless the game has a separate guaranteed-drop or pity rule.

Does each attempt have to be independent?

Yes. The formula assumes each attempt has the same fixed probability and is independent of all others, so past misses never raise the next roll. Games with a pity system break this rule on purpose; enter the pity count to model a hard guarantee.

How does a pity system change my odds?

With hard pity at N attempts, the drop is certain by attempt N, so the chance after n tries is 1 − (1 − p)^n for n below N and 100% from N on. The mean attempts per drop falls from 1 ÷ p to (1 − (1 − p)^N) ÷ p. At 0.6% with pity at 90, the mean is about 70 attempts instead of 167. Soft pity, where the rate climbs before the cap, is game-specific and not modeled.

What is the chance of getting 2 or more drops?

Use the binomial distribution: P(X ≥ k) = 1 − Σ P(X = j) for j below k, with P(X = j) = C(n, j) p^j (1 − p)^(n − j). At a 1% rate over 300 kills, the chance of at least 2 drops is 80.2% and of at least 3 is 57.8%. Set Copies needed to k to see the chance and the tries required.

How many attempts do I need for a 50% chance?

The result panel shows the exact number. Mathematically it is ceil(log(0.5) / log(1 − p)). For a 1% drop rate that is 69 attempts.

Why is a displayed 100% not always a guarantee?

For a fixed probability below 100%, the mathematical result approaches but does not reach 100%. A displayed 100.00% can therefore be a rounded value. Only a per-attempt rate of 100% or a documented guarantee makes success certain.

Can I enter odds such as 1 in 128?

Yes. Select “1 in N” and enter 128. The calculator converts that to an exact per-attempt probability of 1/128. You can also use percentage mode for rates such as 0.5% or 0.01%.

How many tries do I need for a 90% or 99% chance?

Use n = ln(1 − target) ÷ ln(1 − p), rounded up. At a 1% drop rate that is 230 tries for 90% and 459 for 99%; at 5% it is 45 and 90. In general 90% takes about 2.3 times the drop odds and 99% about 4.6 times, so a 1 in 512 drop needs 1,178 tries for 90% and 2,356 for 99%.

Am I unlucky if I have gone dry for twice the drop rate?

Going dry for twice the odds happens to about 13.4% of players (close to e^−2), and three times the odds to about 5%. So 200 kills without a 1/100 drop is unlucky but common; the dry-streak figure in the result shows your exact percentile.

Does the calculator know the drop rate for my game?

No. It has no game database. Enter the published or community-tested rate for your item, for example from the game's wiki or patch notes, and the calculator does the probability math.

Loot Drop Chance Calculator

Enter a per-attempt drop rate and attempt count to see the chance of at least one drop (or of k copies), tries needed for 50/90/99%, and how a pity guarantee changes the odds.

The chance of at least one drop in n tries is 1 − (1 − p)^n, where p is the drop rate per try.

Drop Parameters

Drop Rate Format

Per-Attempt Drop Rate (%)

Enter any percentage between 0.0001 and 99.9999

Number of Attempts

Kills, runs, pulls, spins — max 10,000,000

Target Chance (%)

Find the minimum attempts needed for this cumulative chance

Copies Needed

k drops (1–1,000)

Pity at Attempt

Guaranteed by this try

Enter a drop rate and attempt count, then click Calculate.

How Many Drops in 0 Attempts

Binomial distribution, no pity: P(X = j) = C(n, j) · p^j · (1 − p)^{n − j}

Drops	Exactly	At least

Cumulative Probability Curve

Chart will appear after calculation.

Tries Needed by Drop Rate

Minimum attempts for a 50%, 75%, 90%, 95% and 99% chance of at least one drop, with no pity.

Drop rate	%	50%	75%	90%	95%	99%
1 in 4	25%	3	5	9	11	17
1 in 10	10%	7	14	22	29	44
1 in 20	5%	14	28	45	59	90
1 in 50	2%	35	69	114	149	228
1 in 100	1%	69	138	230	299	459
1 in 128	0.781%	89	177	294	382	588
1 in 256	0.391%	178	355	589	766	1,177
1 in 512	0.195%	355	710	1,178	1,533	2,356
1 in 1,000	0.1%	693	1,386	2,302	2,995	4,603
1 in 5,000	0.02%	3,466	6,931	11,512	14,978	23,024
1 in 10,000	0.01%	6,932	13,863	23,025	29,956	46,050

Rule of thumb: 50% takes about 0.69 × the odds, 90% about 2.3 × and 99% about 4.6 ×. Doing exactly the odds (100 kills at 1 in 100) gives only 63.4%.

Quick answer

The chance of at least one drop in n tries is 1 − (1 − p)^n, where p is the drop rate per try. A 1% drop over 100 kills gives 1 − 0.99^100 = 63.4%, not 100%, because each try is independent.

Examples

Drop rate	Tries for 50%	Tries for 90%	Tries for 99%
10% (1 in 10)	7	22	44
5% (1 in 20)	14	45	90
1% (1 in 100)	69	230	459
0.1% (1 in 1,000)	693	2,302	4,603
0.01% (1 in 10,000)	6,932	23,025	46,050

Enter your drop rate and tries to see your odds, copies, pity effect, dry-streak chance and a probability curve.

Summary

This calculator uses the binomial complement formula — P = 1 − (1 − p)^n — to compute the probability of getting at least one loot drop across N independent attempts, and the full binomial distribution for the chance of getting k or more copies. An optional hard-pity count models games that guarantee the item by a fixed attempt. A chart shows how your odds grow, and a reference table lists tries needed for 50% to 99% at common drop rates.

How it works

Choose percentage or 1-in-N format, then enter the fixed per-attempt drop rate.
Enter the number of attempts — kills, dungeon runs, spins, or chests opened.
The calculator applies P = 1 − (1 − p)^n to find the cumulative probability.
Set a target confidence to calculate the minimum whole number of attempts needed to reach it.
Set copies needed above 1 to get the chance of k or more drops, P(X ≥ k), from the binomial distribution, and the tries needed for your target.
Enter a pity count if the game guarantees the drop by attempt N; the chance becomes 100% at N and the mean attempts per drop falls to (1 − (1 − p)^N) ÷ p.
The result also shows the dry-streak chance, expected drops, a 0/1/2/3/4+ drop distribution, 50%, 75%, 90% and 99% milestones, and the mean attempts per drop.
A probability curve chart updates in real time so you can see how odds improve with more attempts.

Use cases

Estimate how many boss kills are needed to obtain a rare weapon.
Plan farming sessions in MMORPGs and ARPGs before spending time grinding.
Calculate dungeon run counts needed for a specific drop in games like World of Warcraft or Path of Exile.
Understand gacha pull probabilities across multiple rolls.
Compare the efficiency of different farming spots with different drop rates.
Determine when it becomes statistically likely (>50% or >90%) that a drop has occurred.
Settle debates with friends about how unlucky or lucky a farming session was.

Frequently Asked Questions

Last updated: 2026-10-09 · Reviewed by Nham Vu