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Tools/CIDR

CIDR

Network, mask, range, host count, and containment for IPv4 CIDR. Nothing is uploaded.

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How to use CIDR

  1. 1. Paste CIDR. Address plus prefix.
  2. 2. Read network, broadcast, first/last, hosts. /31 and /32 special-cased.
  3. 3. Test an IP. Contains true/false.
  4. 4. No whois. Math only.

About this tool

CIDR math is bitwise AND. This calculator shows network, broadcast, usable range, mask, and host count for IPv4, and tests whether an address sits in the prefix.

/31 and /32

Point-to-point and host routes do not reserve network/broadcast the way /24 does.

IPv6

Not implemented here.

Code examples

CIDR

10.0.0.0/24

Frequently asked questions

Hosted APIs for this job

We do not run these services. Each guide has Free / Freemium / Paid labels and a link to official docs.

FreeFreemium

IP address to location API

City, region, country, ASN, and ISP from an IP. Compare ip-api (free, HTTP, non-commercial), IPinfo, and ipapi.co.

Free

What is my public IP API

Return the caller’s public IPv4 or IPv6. ipify (JSON) and Cloudflare trace. Both free, no key.

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