IPv4 Range & CIDR Calculator
Convert IPv4 ranges to the minimal CIDR list, list their addresses, or expand a CIDR block
Input
Paste a range such as 10.0.0.5 - 10.0.0.100 to fill both fields.
The end address is included in the range.
Results
- Start address
- 10.0.0.5
- End address
- 10.0.0.100
- Address count
- 96
- CIDR blocks
- 8
Minimal CIDR list
The fewest non-overlapping blocks that cover exactly this range.
- Block 1
- 10.0.0.5/32
- 10.0.0.5 – 10.0.0.5 · Size: 1
- Block 2
- 10.0.0.6/31
- 10.0.0.6 – 10.0.0.7 · Size: 2
- Block 3
- 10.0.0.8/29
- 10.0.0.8 – 10.0.0.15 · Size: 8
- Block 4
- 10.0.0.16/28
- 10.0.0.16 – 10.0.0.31 · Size: 16
- Block 5
- 10.0.0.32/27
- 10.0.0.32 – 10.0.0.63 · Size: 32
- Block 6
- 10.0.0.64/27
- 10.0.0.64 – 10.0.0.95 · Size: 32
- Block 7
- 10.0.0.96/30
- 10.0.0.96 – 10.0.0.99 · Size: 4
- Block 8
- 10.0.0.100/32
- 10.0.0.100 – 10.0.0.100 · Size: 1
Addresses: 96 · CIDR blocks: 8
Related Tools
What it calculates
Enter a start and end IPv4 address to get the exact address count and the minimal list of CIDR blocks that covers the range, for example 10.0.0.5 to 10.0.0.100 becomes eight blocks from 10.0.0.5/32 to 10.0.0.100/32. Range to Addresses previews the individual addresses, and CIDR to Range turns a block such as 172.16.5.4/20 into its first and last address, size, subnet mask and wildcard mask.
How the minimal CIDR list is built
From the start address the calculator takes the largest block that is aligned on that address, halves it until it ends inside the range, writes it down and continues after it. The blocks never overlap, cover exactly the range you entered and number at most 62 for IPv4, so even 0.0.0.0 to 255.255.255.255 resolves instantly to 0.0.0.0/0 without listing a single address.
Large ranges and limits
The address preview renders at most the first 1,000 rows and always shows the real total. Copy all and the text or CSV download are available for ranges of up to 100,000 addresses; larger ranges keep the preview and point you to the CIDR list instead, so the browser never builds millions of rows.
Input rules and privacy
Addresses must be four decimal octets: leading zeros, short forms such as 10.1 and IPv6 are rejected with a message instead of being guessed. A reversed range is reported with a Swap action rather than silently swapped, and a pasted range such as 10.0.0.5 - 10.0.0.100 fills both fields. Everything is calculated in your browser and nothing you type is stored or sent.
