The practical guide / 03
A little perspective
on probability.
Explore the odds in a simple random prize draw. Change the numbers to see how entry counts and winning entries affect the chance of at least one win.
Use whole numbers from 1 to 1,000,000. Total entries includes your entries. Your entries and winning entries cannot exceed the total.
An illustration, not a prediction. Assumes equally likely valid entries and a random draw without replacement. Actual competition rules may differ.
Understand the model
Useful maths. Clear assumptions.
All entries have equal weight
Every valid entry must have the same chance of selection. Judged competitions and weighted draws need a different model.
The draw is without replacement
Each winning entry is removed before the next is picked. The calculation does not assume that every prize is won by a different person.
The input determines the result
Total entries includes your own entries. If the promoter has not published a total, your result is only a scenario based on your estimate.
What does this calculator measure?
It calculates the chance that at least one of your entries is selected when a fixed number of winning entries is drawn uniformly at random, without replacement, from all valid entries.
Does it predict whether I will win?
No. The result is a probability under the stated assumptions, not a forecast or guarantee. You need the true total entry count, and many promoters do not publish it.
Can I use this for judged competitions?
No. Judged entries, weighted entries, restrictions on repeat winners and different draw rules do not fit this model. Always read the promoter’s rules.
Does entering more improve my chances?
Within this model, more valid entries increase your chance. Only submit entries permitted by the rules, and treat comping as a hobby rather than expected income.