Network Tools

IPv4 Range to CIDR

Split an IPv4 start/end range into the minimal exact set of CIDR blocks.

IPv4 range to CIDR
Builds the minimal set of CIDR blocks that exactly covers the range.
64Total addresses
1CIDR blocks
3232238080Start decimal
3232238143End decimal
Exact CIDR cover
CIDRAddresses
192.168.10.0/2664

IPv4 Range to CIDR

Convert an inclusive IPv4 start/end range into the smallest set of CIDR blocks that covers it exactly without including outside addresses.

Use Cases

  • Rewrite firewall or access-control ranges as CIDR
  • Verify address counts and decimal forms
  • This tool handles IPv4 only, not IPv6

Frequently Asked Questions

Why does one range split into multiple CIDRs?
CIDR boundaries must align to powers of two (a /24’s third octet must be a multiple of its block size), and arbitrary start-end ranges rarely align. The tool covers your range exactly with the minimal set of CIDRs — 10.0.0.5–10.0.0.10 splitting into several blocks is correct behavior.
How do I verify nothing was over- or under-covered?
The tool lists each CIDR with its address count; the sum must equal your input range length. Reconcile totals before pushing bulk firewall rules — that is how you avoid the "allowlist accidentally admitted the neighboring subnet" incident.
Does it support IPv6 ranges?
This tool handles IPv4. IPv6 allocation practice is CIDR-native anyway (arbitrary ranges are rare), and expanding a 128-bit range can produce an explosion of blocks — plan with aligned prefixes from the start.