CIDR to IP Range Converter
Turn a CIDR block into its first and last address, or an IPv4 or IPv6 range into the fewest CIDR blocks that cover it exactly.
CIDR to IP Range Converter
For example 10.0.0.0/22, 10.0.0.5 - 10.0.0.20 or 2001:db8::/48
16 addresses from 192.168.0.5 to 192.168.0.20, in 5 blocks.
Quick facts
- Price
- Free
- Sign-up
- Not required
- Where it runs
- On your device
- Files uploaded
- No
- Limits
- Up to 200 bytes per input
- Updated
CIDR to IP Range Converter turns a CIDR block into its first and last address, or a range of IPv4 or IPv6 addresses into the fewest CIDR blocks covering it. It helps when a firewall, a cloud security group or an allow list takes only CIDR notation but you were given a start and end address, or the other way round.
How to use
- To expand a block, type it with its prefix, such as
10.0.0.0/22or2001:db8::/48. The table shows the first and last address, how many addresses the block holds and, for IPv4, the subnet mask. - To turn a range into blocks, type the start and end joined by a dash or the word “to”, such as
10.0.0.5 - 10.0.0.20. Both ends are included. - The blocks appear one per line, ready to copy into a configuration file. If an address is inside a block rather than at its start, a note names the block it belongs to.
Examples
192.168.0.5 - 192.168.0.20 holds 16 addresses, but they do not line up with one block, so the answer is five: 192.168.0.5/32, 192.168.0.6/31, 192.168.0.8/29, 192.168.0.16/30 and 192.168.0.20/32. Each block starts on a multiple of its own size, which is why the edges need small blocks.
2001:db8::/32 runs from 2001:db8:: to 2001:db8:ffff:ffff:ffff:ffff:ffff:ffff, which is 79,228,162,514,264,337,593,543,950,336 addresses.
Limits
The start and end of a range must be the same family; it does not mix IPv4 and IPv6. IPv6 addresses with a zone, such as fe80::1%eth0, are refused, and so are IPv4 numbers with leading zeros, because programs disagree on whether 010 is octal. IPv6 results are written in the short form of RFC 5952.
FAQ
Why does my range need more than one block?
A CIDR block always holds a power of two addresses and starts at a multiple of that size. A range that starts or ends anywhere else can only be covered exactly by several blocks of different sizes. The tool picks the largest block that fits at each step, which gives the smallest list.
Can I type an IPv4 address embedded in IPv6?
Yes. A form such as ::ffff:192.0.2.1 is read, and its last 32 bits come from the dotted part. IPv4-mapped addresses in the answer keep that dotted ending, as RFC 5952 recommends, so ::ffff:c000:201 is written ::ffff:192.0.2.1.
Related tools
- Subnet CalculatorWork out the network, broadcast, mask, wildcard and usable host range of any IPv4 address and prefix, from /0 to /32.
- VLSM CalculatorSplit one IPv4 network into subnets of different sizes, largest first, each sized for the hosts you need, with no overlap.
- IPv6 Address Expander and CompressorExpand an IPv6 address to all eight groups, or compress it to the one canonical short form that RFC 5952 defines.