IP/CIDR Calculator

Check if IP addresses fall within CIDR ranges, calculate subnet details, and verify webhook provider IP allowlists.

Check if an IP is within a CIDR range

IP Address

CIDR Range

In Range

10.0.0.50 is within 10.0.0.0/24

Always verify the source — Use HMAC signature verification as the primary authentication method. IP allowlisting should be a secondary defense layer, not the only one.
Use CIDR ranges over individual IPs — Providers often rotate individual IPs within their published CIDR blocks. Allowlisting the entire range avoids service disruptions.
Automate range updates — Some providers (like GitHub) expose their IP ranges via an API endpoint. Poll these periodically to keep your firewall rules current.
Log denied requests — Monitor blocked webhook deliveries so you can quickly detect and resolve allowlist misconfigurations.

/32 — A single host address. Used when a provider publishes individual IPs.
/24 — 256 addresses (254 usable). The most common subnet size for small networks.
/16 — 65,536 addresses. Often used for larger organizational allocations.
/8 — 16.7 million addresses. Major network blocks like 10.0.0.0/8 for private networks.
The prefix number indicates how many bits of the 32-bit IPv4 address are fixed. The remaining bits define the range of available host addresses.

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Check if IP addresses fall within CIDR ranges, calculate subnet details, and verify webhook provider IP allowlists.

Check if an IP is within a CIDR range

IP Address

CIDR Range

In Range

10.0.0.50 is within 10.0.0.0/24

Always verify the source — Use HMAC signature verification as the primary authentication method. IP allowlisting should be a secondary defense layer, not the only one.
Use CIDR ranges over individual IPs — Providers often rotate individual IPs within their published CIDR blocks. Allowlisting the entire range avoids service disruptions.
Automate range updates — Some providers (like GitHub) expose their IP ranges via an API endpoint. Poll these periodically to keep your firewall rules current.
Log denied requests — Monitor blocked webhook deliveries so you can quickly detect and resolve allowlist misconfigurations.

/32 — A single host address. Used when a provider publishes individual IPs.
/24 — 256 addresses (254 usable). The most common subnet size for small networks.
/16 — 65,536 addresses. Often used for larger organizational allocations.
/8 — 16.7 million addresses. Major network blocks like 10.0.0.0/8 for private networks.
The prefix number indicates how many bits of the 32-bit IPv4 address are fixed. The remaining bits define the range of available host addresses.

Get started free with no credit card required.