Random Choice Generator

Using the random choice generator

1. Write your options in the Choose from box, one on each line. You can also paste a column copied from a spreadsheet.
2. Leave Choose at 1 for a single pick, or enter how many different items you want.
3. Tick Remove duplicates from list if some lines are repeated and you want each distinct option to count once.
4. Press Choose Randomly. The picked items are listed in the order they were drawn.

Each line is one option, so entries such as Pasta night or Rock, paper, scissors stay whole. Blank lines are skipped and spaces at the start or end of a line are trimmed. If a pasted spreadsheet row contains tabs, the cells of that row are joined with commas and treated as one item.

How many items can be chosen?

You can ask for anything from one item up to the number of lines on your list, within a ceiling of 100,000 picks. Asking for more than the list holds produces an error, since nothing can be picked twice from the same line. If you choose exactly as many items as there are lines, you simply get your whole list back in a random order; the list randomizer is built for that job.

The list needs at least two options, because a choice between one thing is no choice. With the duplicate option on, the two options must be different.

How fair is the pick, and what are the odds?

Every line has the same chance, wherever it sits in the list. Items are drawn without replacement, which means a line that has been picked is out of the running for the remaining draws. If k items are chosen from n lines, the chance that any particular line is among them, and the number of different ordered results, are:

P(line is picked) = k ÷ n

ordered results = n × (n − 1) × … × (n − k + 1)

Example: choosing 3 items from 8 gives every line a 3 ÷ 8 = 37.5% chance, and there are 8 × 7 × 6 = 336 possible ordered results.

Repeated lines are a deliberate way to weight a draw. In a list with pizza written three times and sushi once, the first pick is pizza with probability 3 ÷ 4 = 75%. Tick the duplicate option and both would be 50%.

Is the random choice truly random?

The picks come from your browser's cryptographically strong random number generator, falling back to the standard one only if that is missing. The selection method is a partial shuffle with unbiased index drawing, so no ordering or position is favored. It is pseudo-random rather than physical randomness such as coin flips or dice, but for decisions, draws and games there is no practical difference, and nothing can be predicted from earlier results.

When a random pick helps

• Settling small decisions: where to eat, which film to watch, who starts.
• Choosing one student, volunteer or entry from a class or contest list. Keep a copy of the list and the result if the draw needs to be shown to others.
• Ordering tasks by lottery when none has priority.
• Picking prompts, topics or questions for games and quizzes.

For a physical-style throw see the dice roller, and to split people into groups use the random team generator.