Roll number picker
This roll number picker chooses students fairly: enter the last roll number of your class, press “Pick a roll number” and one number appears large on the screen. Numbers that have had their turn are struck off, so every student is called exactly once before anyone is called again.
Source: W3C Recommendation, W3C Web Cryptography API – getRandomValues(). Updated: .
How it is calculated
The roll number picker draws one roll number from your class at random and without repeats: each number comes up only once until every student has had a turn. You no longer have to remember who has already answered, and the class can see that the choice is fair.
How to pick a random roll number
- Set “Last roll number” to the strength of your class, for example 40.
- Type the roll numbers of absent students into “Absent roll numbers”.
- Press “Pick a roll number”. The student with that number is up.
- Repeat for the next student. The list “Already called” keeps the order.
What teachers use it for
| Classroom situation | Setting |
|---|---|
| Oral questions, reading aloud, board work | 1 roll number per pick |
| Order of seminar or project presentations | pick until the list is empty, then copy the order |
| Quick groups for an activity | “Roll numbers per pick” = 4 gives a group of four each time |
| Viva voce or lab practical order | first and last roll number of the batch, e.g. 21 to 40 |
| Class monitor or duty for the week | one pick; exclude those who have already served |
How fair is the draw?
Every roll number that has not been called yet has the same chance. In a class of 40, each student has a chance of 1/40 = 2.5% on the first pick; when 10 students are left, it is 1/10 = 10%. The numbers come from the browser’s cryptographic random number generator, not from a pattern someone could predict – and not from the teacher’s mood.
Why numbers instead of names?
Working with roll numbers means no student names are entered anywhere. Nothing personal is stored or shared, the page is ready in seconds for any section, and you can project it in class without showing a name list. If you would rather draw names, use the random name picker; for a seating plan, the classroom seating chart generator.
Roll numbers that do not start at 1
Sections often have a block of numbers – say 61 to 120 – or university roll numbers with a long prefix. Enter the first and last number of the block. For long registration numbers, use only the last two or three digits that differ from student to student.
Keeping the list for the next period
The numbers already called are stored in the page, so a reload does not reset the draw. The share button creates a link with the current state – send it to yourself on WhatsApp and continue in the next period where you stopped. “Start again” clears the list for a new round.
Frequently asked questions
How do I pick a random roll number?
Enter the last roll number of the class and press “Pick a roll number”. One number from the range appears; it will not be picked again until you start a new round.
Can the same roll number come up twice?
No. A number that has been picked is struck off. Only after “Start again” are all numbers back in the draw.
How do I leave out absent students?
Type their roll numbers into “Absent roll numbers”, separated by commas or spaces. They are skipped for as long as they stay in that box.
Can I pick several roll numbers at once?
Yes. Set “Roll numbers per pick” to the group size, for example 4. Each press then gives four different numbers.
Does it work for a class of more than 100 students?
Yes. Set the first and last roll number to any range you need; lecture halls with several hundred students are no problem.
Is the picker truly random?
It uses the browser’s cryptographic random number generator. Every number still in the draw has exactly the same chance.
Can I undo a pick made by mistake?
“Take back the last pick” puts the last number back into the draw.
Do I need to enter student names?
No. The tool works with roll numbers only, so no personal data is entered, stored or shared.
Sources and legal basis
- W3C Recommendation: W3C Web Cryptography API – getRandomValues()
- MDN Web Docs – Crypto.getRandomValues()
- Fisher–Yates shuffle (Durstenfeld 1964)
As of: · Editorial policy
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