OSRS Dry Calculator
Drop rate and dry streak calc. Enter a drop rate and your kill count to see how dry (or lucky) you are and how many kills most players need.
Accepts 1/512, 512 or 0.2%
Kills, chests, caskets or attempts
0 if you are still dry
How to read this
Chance of being this dry is the probability of zero drops in your kill count: (1 − 1/rate)^kills. At exactly the drop rate it is 36.8%, at twice the rate 13.5%, at three times 5.0%. It does not depend on the rate itself, only on how many multiples of the rate you have done.
Players with more drops is the share of players who, at your kill count, would have more than you. It is the honest luck percentile: 90% means nine in ten would be ahead of you.
Median kills is the 50% point, always lower than the rate because probability compounds. For a 1/512 drop the median is 355 kills; the mean is the full 512.
Rolls per kill matters for monsters that roll their table more than once per kill. Two rolls at 1/512 is an effective 1/256.5 per kill, not 1/256, because both rolls can hit.
Raid purple calculator: ToA, CoX and ToB
Raid uniques are not a flat drop rate. Tombs of Amascut and Chambers of Xeric roll on points, so your purple chance changes every raid; Theatre of Blood rolls a fixed chance per deathless completion. Enter your raid level and points to get the purple chance for that raid, the odds of each specific item, and how many raids a 50% or 90% chance takes.
Invocation level shown on the raid setup screen.
Total for the whole team, after the game removes each player's 5,000 starting points. A solo 300 is usually 20,000-30,000.
Leave blank for a solo. In a team the purple goes to one player, weighted by points.
| Item | Share of purples | Chance per raid (yours) | Raids for 50% | Raids for 90% |
|---|---|---|---|---|
| Osmumten's fang | 29.2% | 1.620% (1/61.7) | 43 | 141 |
| Lightbearer | 29.2% | 1.620% (1/61.7) | 43 | 141 |
| Elidinis' ward | 12.5% | 0.694% (1/144) | 100 | 331 |
| Masori mask | 8.3% | 0.463% (1/216) | 150 | 497 |
| Masori body | 8.3% | 0.463% (1/216) | 150 | 497 |
| Masori chaps | 8.3% | 0.463% (1/216) | 150 | 497 |
| Tumeken's shadow | 4.2% | 0.231% (1/432) | 300 | 994 |
Shares follow the wiki table (150-300, 350, 400, 450, 500) and are interpolated every 5 levels in between, as the game does. Below raid level 50 the fang, and below 150 the shadow, need an extra 1/50 roll; the calculator does not apply that reduction.
Formula: 1% chance per (10,500 − 20 × RL) reward points, where RL = raid level up to 310, then 310 + (level − 310) / 3 up to 430, then 350 + (level − 430) / 6. At 400 that is 3,700 points per 1%. Source: OSRS Wiki, Tombs of Amascut chest, checked 17 September 2026.
Dry streak odds at a glance
The chance of going dry depends only on how many multiples of the drop rate you have done, not on the rate itself. These values hold for any 1/x drop once x is more than a few dozen.
| Kills done | Chance of still being dry | Players who have it by now | Example at 1/512 |
|---|---|---|---|
| 0.5× the rate | 60.7% | 39.3% | 256 kills |
| 0.69× the rate (median) | 50.0% | 50.0% | 355 kills |
| 1× the rate | 36.8% | 63.2% | 512 kills |
| 1.5× the rate | 22.3% | 77.7% | 768 kills |
| 2× the rate | 13.5% | 86.5% | 1,024 kills |
| 2.3× the rate | 10.0% | 90.0% | 1,178 kills |
| 3× the rate | 5.0% | 95.0% | 1,536 kills |
| 4× the rate | 1.8% | 98.2% | 2,048 kills |
| 4.6× the rate | 1.0% | 99.0% | 2,356 kills |
| 5× the rate | 0.67% | 99.33% | 2,560 kills |
| 7× the rate | 0.09% | 99.91% | 3,584 kills |
| 10× the rate | 0.0045% | 99.9955% | 5,120 kills |
How a dry calculator works
Every kill is an independent roll. A 1/512 drop has a 511/512 chance of not appearing on any given kill, so the chance of nothing in k kills is (511/512)^k. That is the geometric distribution, and it is why the odds never reach zero: at ten times the rate there is still a 1 in 22,000 chance of nothing.
The number of drops you have after k kills follows the binomial distribution, which is what the bar chart above shows. Comparing your count against that distribution is the only fair way to answer "how lucky am I" once you have one or more drops: two twisted bows in 800 solo raids is a very different statement from zero.
The mean number of kills to a drop equals the rate, but the median is 69.3% of it, because the distribution has a long right tail. Half of players get a 1/512 drop inside 355 kills; the unlucky half stretches the average out to 512. Rolls per kill change the effective rate: two rolls at 1/512 is 1 − (511/512)² per kill, an effective 1/256.5.
Raid uniques work differently. Tombs of Amascut gives a 1% unique chance for every 10,500 − 20 × RL reward points, where RL is a scaled raid level, capped at 55%. Chambers of Xeric gives 1% per 8,676 team points, capped at 65.7%, with points past 570,000 rolling a second unique. Theatre of Blood is a flat 1/9.1 for a deathless Normal Mode team and 1/7.7 in Hard Mode. All three then pick an item from a weighted table, which the raid calculator applies for you.
Dry calculator FAQ
How do I use this OSRS dry calculator?
Enter the drop rate as 1/x (or pick a preset), your kill count, and how many of the drop you already have. You get the chance of your exact outcome, the share of players who would have more drops than you, expected drops, the median, the kill counts for a 50%, 90% and 99% chance, the full drop-count distribution, and a link you can share. Add kills per hour to turn every figure into hours.
How dry am I?
Look at the 'players with more drops' tile. At 90% you are in the driest tenth of players at your kill count; at 95% the driest twentieth; at 99% the driest hundredth. With zero drops it equals the chance that a player has at least one by now, which is 63.2% at the rate, 86.5% at twice the rate and 95% at three times the rate.
What are the odds of going 2x dry in OSRS?
About 13.5% for any drop rate, because (1 - 1/x)^(2x) tends to e^-2. Going 3x dry is about 5%, 4x about 1.8%, 5x about 0.67% and 10x about 0.0045%. For a 1/512 drop that means 1,024 kills without it happens to roughly one player in seven.
Why is the median lower than the drop rate?
The median is 69.3% of the rate: for a 1/512 drop, half of players have it within 355 kills. The mean is the full 512 because a small share of players go very dry and pull the average up. That right-skewed shape is normal for geometric distributions, not a sign that rates are wrong.
How is the Tombs of Amascut purple chance calculated?
Per the OSRS Wiki, you have a 1% unique chance for every 10,500 - 20 x RL total reward points, where RL is a scaled raid level: the raid level itself up to 310, then 310 + (level - 310) / 3 up to 430, then 350 + (level - 430) / 6 above that. At raid level 400 that is one percent per 3,700 points. The chance is capped at 55% and the game subtracts the 5,000 starting points before rolling. Between levels 305 and 500 the fang and Lightbearer become less likely and the other uniques more likely.
How is the Chambers of Xeric purple chance calculated?
Every 8,676 total team points is a 1% chance of a unique, capped at 65.7% at 570,000 points. Points beyond the cap roll for a second unique, so 855,000 points is 65.7% for the first and 32.85% for a second. Which teammate receives it is weighted by personal points. The item is then picked from a weighted table: the prayer scrolls are 14/60 each and the twisted bow 2/60 in normal mode.
What is the Theatre of Blood purple chance?
A deathless team has a 1/9.1 (about 11%) chance of a unique in Normal Mode and 1/7.7 (about 13%) in Hard Mode, regardless of team size. Deaths lower the chance. The item goes to one player, weighted by deaths and damage, with the MVP most likely. The avernic defender hilt is 8/19 of purples in Normal Mode and the scythe 1/19.
How is this different from the wiki dry calc?
The maths is identical for the basic question. This page adds the distribution of drop counts so you can rate your luck when you have one or more drops, the share of players ahead of you, kills for a 90% and 99% chance, time estimates from your kills per hour, the raid purple calculators for ToA, CoX and ToB, and a shareable link for every result.
Raid formulas and item weights are from the OSRS Wiki pages for the Tombs of Amascut chest, the Ancient chest and the Monumental chest, checked 17 September 2026. Preset drop rates were verified against the wiki in July 2026.
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