Video Game Loot Drop Probability Calculator

Estimate the probability of obtaining at least one specific item from loot drops based on drop rate, number of attempts, and item rarity.

Base Drop Rate (%): Percentage chance per attempt

Number of Attempts: Number of loot drop attempts

Item Rarity: Rarity modifier for drop rate

The probability of obtaining at least one specific item is calculated using the binomial probability model.

Effective Drop Rate:
\\[ p_{\text{eff}} = \frac{R \cdot M}{100} \\]

Where:
- \\( p_{\text{eff}} \\): Effective drop probability
- \\( R \\): Base drop rate (%)
- \\( M \\): Rarity modifier (1.0, 0.5, 0.2, or 0.05)
Probability of Zero Successes:
\\[ P(X = 0) = (1 – p_{\text{eff}})^n \\]

Where:
- \\( n \\): Number of attempts
Probability of At Least One Success:
\\[ P(X \geq 1) = 1 – P(X = 0) = 1 – (1 – p_{\text{eff}})^n \\]
Percentage Probability:
\\[ P_{\text{percent}} = P(X \geq 1) \cdot 100 \\]

Likelihood levels: Low (0–25%), Moderate (25–50%), High (50–75%), Very High (75–100%).

Inputs: Base Drop Rate = 10%, Attempts = 20, Item Rarity = Common (1.0)

Calculations:

Result: Drop Probability: 87.8% (Very High)

Inputs: Base Drop Rate = 5%, Attempts = 50, Item Rarity = Epic (0.2)

Calculations:

Effective Drop Rate: \\[ \frac{5 \cdot 0.2}{100} = 0.01 \\]
Probability of Zero Successes: \\[ (1 – 0.01)^{50} = 0.99^{50} \approx 0.6050 \\]
Probability of At Least One Success: \\[ 1 – 0.6050 = 0.3950 \\]
Percentage Probability: \\[ 0.3950 \cdot 100 \approx 39.5\% \\]
Likelihood Level: Moderate (25–50%)

Result: Drop Probability: 39.5% (Moderate)

Inputs: Base Drop Rate = 2%, Attempts = 100, Item Rarity = Legendary (0.05)

Calculations:

Effective Drop Rate: \\[ \frac{2 \cdot 0.05}{100} = 0.001 \\]
Probability of Zero Successes: \\[ (1 – 0.001)^{100} = 0.999^{100} \approx 0.9048 \\]
Probability of At Least One Success: \\[ 1 – 0.9048 = 0.0952 \\]
Percentage Probability: \\[ 0.0952 \cdot 100 \approx 9.5\% \\]
Likelihood Level: Low (0–25%)

Result: Drop Probability: 9.5% (Low)

Follow these steps to estimate the probability of getting a loot drop:

Enter Base Drop Rate: Input the base drop rate in % (0.01–100, e.g., 5). Use the decimal button (.) for precision.
Enter Number of Attempts: Input the number of attempts (1–1000, e.g., 50).
Select Item Rarity: Choose common (1.0), rare (0.5), epic (0.2), or legendary (0.05) from the dropdown.
Calculate: Click “Calculate Drop Probability” to see the result.
Interpret Result: The result shows the probability in % with a likelihood level (Low: 0–25, Moderate: 25–50, High: 50–75, Very High: 75–100). If you see “Please fill in all fields,” ensure all inputs are valid.
Share or Embed: Use the share buttons to post results on social media, copy the result, or get an embed code.

Note: This is a simplified model assuming independent drops. Actual game mechanics may include pity timers, streaks, or other modifiers.

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