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Gaming Runs in browser Updated 30 Mar 2026

Drop Rate Calculator

Calculate loot drop probabilities, dry streak odds, and how many farming runs you need for 50%, 90%, or 99% confidence. Works for any game or drop rate.

Results for 100 attempts

At least one drop

63.40%

Dry streak (0 drops)

36.60%

50% confidence

69 runs

90% confidence

230 runs

99% confidence

459 runs

Probability curve

40%
51
63%
100
64%
102
79%
153
87%
204
92%
255
95%
306
97%
357
98%
408
99%
459

Attempts

Quick reference — attempts needed at 1% drop rate

ConfidenceAttempts
50%69
75%138
90%230
95%299
99%459

Assumes each attempt is independent with a fixed drop rate. Does not account for pity systems, bad luck protection, or pseudo-random distribution that some games use.
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How to use Drop Rate Calculator

  1. Enter the drop rate

    Type the item's drop rate as a percentage, or click a preset button (50%, 10%, 5%, 1%, 0.1%, 0.01%) for common farming scenarios.

  2. Enter your number of attempts

    Type how many kills, runs, or attempts you have completed or plan to complete. This calculates your current or projected probability.

  3. Read your results

    View the probability of at least one drop, the dry streak chance, and expected attempts for 50% through 99% confidence — all updating live as you type.

  4. Check the probability curve

    Scroll down to see a live chart showing how your drop probability grows with each additional attempt, with your entered attempt count highlighted on the curve.

Drop Rate Calculator FAQ

How is loot drop probability calculated?
The probability of getting at least one drop in N attempts is P = 1 − (1 − r)^N, where r is the drop rate as a decimal. This assumes each attempt is independent with the same drop rate — the standard model for most loot systems in games.

What does dry streak probability mean?
Dry streak probability is the chance of getting zero drops across all your attempts. It equals (1 − r)^N. For example, with a 1% drop rate and 100 attempts, there is a 36.6% chance you get nothing at all — which is why farming rare items can feel so punishing.

How many runs do I need for a 99% chance of getting a drop?
The number of attempts for 99% confidence equals ⌈log(0.01) ÷ log(1 − r)⌉. For a 1% drop rate that's 459 attempts. For a 0.1% drop rate it's 4,603 attempts. Probability approaches 100% asymptotically — it never actually reaches it.

Does this work for OSRS drop rates?
Yes. Old School RuneScape uses independent per-kill drop rates. Enter the rate as a percentage (e.g. 1/512 = 0.195%) and the calculator gives you exact probability, expected kills, and dry streak odds.

Does this work for gacha games with pity systems?
The base formula works for independent rolls. Gacha pity systems guarantee a pull after N attempts, which changes the probability model. The calculator shows your base probability without pity — actual rates are higher for games with soft or hard pity.

What if my drop rate is expressed as a fraction like 1/256?
Convert the fraction to a percentage: 1/256 = 0.390625%. Enter 0.390625 in the drop rate field. The calculator accepts any decimal precision.

Is a 1% drop rate really that rare?
With a 1% drop rate you need 69 attempts for a 50% chance and 459 attempts for a 99% chance. Many players underestimate how many farming runs truly rare items require — this is by design in most games to extend playtime.

Can I use this for Warframe, Diablo, or Path of Exile?
Yes. All three games use per-attempt drop rates for most items. Enter the listed drop percentage and your completed runs to see your probability. Diablo and PoE magic-find mechanics change the effective drop rate — use the improved rate in that case.

Background

Find out exactly how lucky or unlucky you are with the Drop Rate Calculator. Enter any drop rate percentage and number of attempts to instantly see the probability of getting at least one drop, the chance of a complete dry streak, and how many runs you need for 50%, 75%, 90%, 95%, and 99% confidence.

A live probability curve shows how your odds improve with each additional attempt, helping you decide whether that next farming run is worth your time. Preset buttons for common drop rates — 50%, 10%, 5%, 1%, 0.1%, 0.01% — let you jump to popular loot scenarios instantly.

Works for any game with independent per-attempt drop chances: MMOs, ARPGs, gacha games, looter shooters, survival games, and classic RPGs. All calculations use P = 1 − (1 − r)^N, the standard binomial probability model. Note: games with pity systems or bad-luck protection require additional modelling not covered by this calculator.

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