Category: Calculators
Prime Number Generator
List every prime in a range, or the first N primes, instantly
Generate every prime number in a range, or the first N primes starting from 2, using a sieve of Eratosthenes that runs entirely in your browser.
Uses a sieve of Eratosthenes; very wide ranges or large counts are capped so the tab stays responsive.
Everything on this page is processed in your browser. Nothing is uploaded.
What this tool does
This tool uses a sieve of Eratosthenes, the standard fast algorithm for listing every prime up to a limit, rather than testing each number individually the way the Prime Number Checker does. In range mode it sieves up to the top of your range and keeps the primes at or above the bottom; in count mode it estimates an upper bound for the Nth prime, sieves up to that bound, and doubles the bound if the estimate came in short. Very wide ranges or large counts are capped so the tab stays responsive.
How to use it
- Choose whether to generate primes in a range, or the first N primes.
- Enter the range bounds, or how many primes you want.
- Copy or download the resulting list.
Privacy
This tool runs entirely in your browser. Your input is never uploaded, stored or shared — closing the tab removes it.
Frequently asked questions
- What is the difference between this and the Prime Number Checker?
- The checker tests whether one specific number is prime. This tool lists many primes at once, either every prime inside a range or the first N primes starting from 2.
- Is there a limit to how many primes I can generate?
- Yes. Range mode is capped at a 2,000,000-wide span up to 10,000,000, and count mode is capped at 10,000 primes, which keeps the sieve fast in a browser tab.
- What algorithm does it use?
- A sieve of Eratosthenes: it marks the multiples of each prime as composite up to the limit, which is much faster than testing every number for primality individually.