CIDR calculator.

Expand a CIDR block into masks, usable hosts, and binary values.

Price
Free, no signup
Category
Calculators
Try
CIDR calculatorWaiting for input

Subnet details appear here.

Enter a CIDR block, or pick an example.

What CIDR notation is.

CIDR (Classless Inter-Domain Routing) writes an IP and its prefix together, such as 192.168.1.0/24.

  • /8 is 255.0.0.0 (16,777,214 usable hosts)
  • /16 is 255.255.0.0 (65,534 usable hosts)
  • /24 is 255.255.255.0 (254 usable hosts)
  • /32 is a single host

How to read the results.

  • Network and broadcast addresses are reserved.
  • Private ranges stay on internal networks.
  • SPF records can authorize a CIDR range instead of listing each IP.

Common questions.

What is CIDR notation?
CIDR notation combines an IP address with a prefix length to define a network range.
What does a /24 mean?
A /24 has 256 total addresses with 254 usable hosts.
Why is CIDR used in SPF records?
CIDR ranges let you authorize blocks of sending IPs instead of listing each address.
What is the difference between subnet mask and wildcard?
The subnet mask defines the network portion, while the wildcard is its inverse for matching.

Plan the send. Let Bento pace it.

Batching controls are built in, and paid plans include unlimited marketing sends, subject to fair use. Plans start at $29/mo for up to 5,000 Active Users.

Start free trialAll free tools