OSRS Pet Probability Comparison
A live comparison of single-roll pet chance, cumulative chance after the entered attempts, and the chance of still being dry.
OSRS Pet Chance Calculator
Estimate cumulative Old School RuneScape pet odds from a per-roll drop rate and number of eligible attempts. The calculator also shows the probability of still being dry and the approximate attempts needed to reach a selected confidence level.
Chance After Attempts
63.22%
- Chance per Eligible Roll
- 0.02%
- Chance of Still Being Dry
- 36.78%
- Expected Attempts
- 5,000 attempts
- Attempts for Target Chance
- 11,512 attempts
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The primary result is cumulative pet chance across the entered attempts. Supporting outputs show single-roll chance, dry chance, expected attempts, and attempts needed for the selected target probability.
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How to Use This Calculator
Enter the pet drop-rate denominator shown for the eligible action, the number of independent eligible rolls, and a target probability such as 50%, 90%, or 95%. Use the correct rate for the exact activity and account state you are modeling.
Formula & Methodology
Single-roll probability is 1 divided by the drop-rate denominator. Cumulative chance after n independent attempts is 1 minus (1 minus p) raised to n. Dry chance is the complement. Attempts for a target probability use the logarithmic inverse of the cumulative formula and are rounded up.
How the OSRS Pet Chance Calculator Works
See the calculation flow used by the OSRS Pet Chance Calculator.
Source: OSRS Wiki
1 in 5,000 pet example
For a 1 in 5,000 pet chance per eligible roll, 5,000 independent attempts do not guarantee the pet. The cumulative probability is about 63.2%, while the dry probability remains about 36.8%.
This model assumes independent eligible rolls with a constant probability. Some OSRS pets use activity-specific formulas, scaling, thresholds, experience-based rates, kill-count modifiers, or other mechanics that cannot be represented by a single fixed 1-in-N rate. Verify the exact pet formula before using the calculator.
Probability does not guarantee an outcome. Being above the expected rate or target probability does not make the next eligible roll certain to succeed.
Related Calculators
- OSRS Drop Rate CalculatorCalculate zero-drop, at-least-one, exactly-k, and target-confidence probabilities for independent OSRS drop rolls.
- OSRS Dry CalculatorCalculate your OSRS dry streak probability, drop chance, expected drops, and the number of kills needed to reach 50%, 90%, 95%, or 99% probability for any drop rate.
- OSRS Slayer CalculatorCalculate OSRS Slayer XP remaining, tasks needed, points earned, estimated time, task cost, loot value, and net value from editable averages.
Related Guides
Frequently Asked Questions
- What does a 1 in N pet rate mean?
- It means each eligible roll has probability 1/N when the activity truly uses a fixed independent rate.
- Does reaching the drop rate give me a 100% chance?
- No. At N attempts on a fixed 1/N rate, cumulative probability is about 63.2%, not 100%.
- What does dry chance mean?
- Dry chance is the probability of receiving no pet across the entered number of eligible attempts.
- Can every OSRS pet be modeled with a single 1 in N rate?
- No. Some pet rates depend on XP, activity, level, scaling, thresholds, or other mechanics. Use this only when a fixed per-roll rate is appropriate.
- Does a high cumulative chance guarantee the next roll?
- No. Past failed rolls do not make the next independent eligible roll certain to succeed.
Published 8/17/2026