Random Number Generator
Set a range and how many numbers you need, then generate. Choose integers or decimals, and allow or prevent duplicates.
Reviewed by the ToolNestr Editorial Team — July 2026
How random number generation works
This tool uses your browser's built-in pseudo-random number generator (PRNG), which produces numbers that appear random by applying a mathematical algorithm to a seed value. The results follow a uniform distribution — every number in the specified range has an equal probability of being selected on each draw.
For integer generation, the PRNG produces a floating-point value between 0 and 1, scales it to your chosen range, and rounds to the nearest integer. When duplicates are disabled, each newly generated number is checked against the existing set and discarded if already taken, repeating until a unique value is found.
Worked example
Generate 10 unique random integers in the range 1–100.
What different range sizes mean
The range you choose affects the granularity and usefulness of your random numbers for different scenarios.
Teacher
Randomly assign students to groups, pick quiz questions, or select a fair sample for classroom activities.
Developer
Generate realistic but random test data to stress-test applications, APIs and database queries.
Event Organiser
Run fair prize draws and raffles by generating unique random ticket numbers and announcing winners.
Gamer
Simulate dice rolls, random encounters, loot drops or any chance-based mechanic in tabletop or video games.
| Mode | Output Type | Best Use Case |
|---|---|---|
| Integers, duplicates OK | Whole numbers, can repeat | Dice rolls, general random picks |
| Integers, no duplicates | Unique whole numbers | Raffles, lottery draws, seat assignments |
| Decimals, duplicates OK | Decimal numbers, can repeat | Simulations, statistical sampling |
| Decimals, no duplicates | Unique decimal numbers | Test data sets, unique IDs |
| Single number | One result | Quick pick, coin flip, yes/no decision |
| Batch (up to 1000) | List of results | Large draws, bulk test data generation |
How to use the random number generator
Set your range
Enter the minimum and maximum values that define the boundaries of your random numbers.
Choose options
Toggle integers or decimals, allow or prevent duplicates, and set how many numbers to generate.
Generate and copy
Click "Generate" to create your numbers, then use "Copy" to save them to your clipboard instantly.
Tips for best results
Disable duplicates for fair draws
For raffles, lottery picks and giveaways, turn off "Allow duplicates" and set the count to match the number of prizes for a completely fair result.
Use decimals for fine-grained simulations
When running simulations or statistical models, use decimal mode with a wide range to get more varied and realistic values.
Match range to your use case
A small range (1–10) is fine for games; use larger ranges for serious draws or test data to ensure sufficient variety.
When to use the random number generator
Random numbers serve different purposes across many fields. In game development, random number generators determine loot drops, enemy spawn locations, procedural world generation, and critical hit mechanics. Game designers rely on seeded random sequences to create reproducible test scenarios while using true random values for live gameplay to ensure fairness and unpredictability.
In statistical sampling and data science, researchers use random number generators to select representative subsets from large populations, shuffle experiment groups, and generate synthetic data for model training. A well-chosen range with no duplicates ensures that every member of a population has an equal chance of being selected, which is the foundation of unbiased statistical inference. The ability to generate both integer and decimal values makes the tool suitable for Monte Carlo simulations and other probabilistic modelling techniques.
Educators and classroom teachers use random number generators for fair group assignments, picking students for presentations, and creating randomised quiz versions to prevent cheating. Event organisers run prize draws and raffles where every ticket number has the same probability of winning, and developers generate unique identifiers and test data for API endpoints and database seeding operations. The no-duplicates mode is especially valuable for any scenario where each outcome must be distinct.
Security and privacy considerations
All random number generation in this tool happens entirely inside your browser using JavaScript's Math.random() function. No data is transmitted to any server, stored in any database, or shared with any third party. The generated numbers exist only on your screen until you copy or close the page. For cryptographic or security-sensitive applications such as encryption key generation, password creation, or secure token generation, the browser's built-in PRNG is not suitable. Use the Web Crypto API's crypto.getRandomValues() method or a dedicated hardware random number generator instead. This tool is designed for everyday use cases like games, draws, and education, not for security-critical operations.
Frequently asked questions
Can I generate numbers without duplicates?
Yes — untick "allow duplicates" and every number generated will be unique (useful for raffles and draws).
Are the numbers truly random?
They use your browser's built-in random generator, which is more than random enough for games, draws and everyday use.
Can I generate decimals?
Yes — untick "integers only" to get decimal numbers within your range.
How many numbers can I generate at once?
Up to 1,000. For very large sets with no duplicates, make sure the range is larger than the count.
What happens if I set a range where min > max?
The calculator will show an error asking you to make the minimum less than or equal to the maximum.
Can I copy the generated numbers?
Yes — click the "Copy" button to copy the full list of numbers to your clipboard.
Are decimals rounded?
Yes, decimals are rounded to 3 decimal places for readability while keeping the output clean.
Can I generate negative random numbers?
Yes — set a negative minimum value (e.g. -50) and a positive maximum to generate across zero.
What is the maximum range I can set?
You can set any range your browser can handle, but very large ranges with decimals may produce less granular values.
Do you store the generated numbers?
No — everything runs in your browser. No data is sent to any server or stored anywhere.