Calculate your chance of winning a raffle, giveaway, multiple tries, or lottery jackpot from entries, tries, and numbers picked for each scenario.
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Chances Of Winning Formula
The calculator uses a different formula depending on the scenario you choose.
Raffle or giveaway
P(\text{win at least once}) = 1 - \frac{C(T-M,W)}{C(T,W)}- P = probability of winning at least one prize
- M = your entries
- T = total entries in the draw
- W = number of winners drawn
- C(n,k) = combinations, the number of ways to choose k items from n items
This mode finds the chance that at least one of your entries is selected. With one winner, the formula simplifies to your entries divided by total entries. With multiple winners, it accounts for winners being drawn without replacement.
Multiple tries
P(\text{win at least once}) = 1 - (1-p)^n- P = probability of winning at least once
- p = chance of winning on one try, written as a decimal
- n = number of tries
This mode assumes each try is independent and has the same chance of winning. It calculates the chance that you do not lose every time.
Lottery
P(\text{jackpot}) = \frac{1}{C(N,k)}- P = probability of matching all numbers
- N = pool size, or how many numbers can be chosen from
- k = numbers you pick
- C(N,k) = total possible number combinations
This mode assumes order does not matter and numbers cannot repeat. It gives the chance of matching the full set of picked numbers.
Common Chance Benchmarks
Use these tables to compare a result from the calculator with typical chance values.
| Probability | Approximate odds | How to read it |
|---|---|---|
| 50% | 1 in 2 | About a coin flip |
| 10% | 1 in 10 | Unlikely, but common over repeated events |
| 1% | 1 in 100 | Rare for one attempt |
| 0.1% | 1 in 1,000 | Very rare |
| 0.000001% | 1 in 100,000,000 | Lottery-grade long shot |
Common lottery jackpot odds
| Lottery format | Total combinations | Jackpot chance |
|---|---|---|
| 6 / 42 | 5,245,786 | 1 in 5,245,786 |
| 6 / 49 | 13,983,816 | 1 in 13,983,816 |
| 6 / 59 | 45,057,474 | 1 in 45,057,474 |
| 5 / 69 | 11,238,513 | 1 in 11,238,513 before any bonus ball |
| 5 / 70 | 12,103,014 | 1 in 12,103,014 before any bonus ball |
Example Problems
Example 1: Raffle with multiple winners
You have 5 entries in a raffle with 500 total entries, and 3 winners are drawn.
P = 1 - \frac{C(500-5,3)}{C(500,3)}P = 1 - \frac{C(495,3)}{C(500,3)} \approx 0.0298Your chance of winning at least one prize is about 2.98%.
Example 2: Multiple tries
You have a 2% chance per try and you try 50 times.
P = 1 - (1-0.02)^{50}P = 1 - 0.98^{50} \approx 0.6358Your chance of winning at least once is about 63.58%.
FAQ
Why do multiple tries not add up directly?
If you have a 2% chance and try 50 times, the chance is not simply 100%. That direct addition ignores the chance that some tries overlap in the sense that you only need one win. The correct method is to calculate the chance of losing every try, then subtract that from 1.
What does “1 in 100” mean?
“1 in 100” means the probability is 1 divided by 100, or 1%. It does not guarantee one win every 100 attempts. It means that over a very large number of similar attempts, the average rate would be about one success per 100 attempts.
Does buying more raffle entries always increase my chance?
Yes, buying or earning more entries increases your chance if all entries are treated equally. However, the size of the increase depends on the total number of entries and the number of winners. Going from 1 to 2 entries matters more in a small raffle than in a raffle with millions of entries.
