CIDR Calculator
Calculate network details from CIDR notation.
Network engineers and developers constantly work with CIDR notation when configuring firewalls, cloud VPCs, and Docker networks. Utilitoo's CIDR Calculator takes a block like 10.0.0.0/16 and instantly returns the network address, broadcast address, subnet mask, wildcard mask, usable host range, and total address count.
Whether you are planning AWS subnet allocations, verifying whether an IP falls within a range, or studying for a networking certification, quick CIDR math saves time and prevents misconfiguration.
Enter CIDR notation and click Calculate. Results include first and last usable host addresses, prefix length, IP class, and total usable hosts. Pair with Subnet Calculator to split networks or IP Lookup for geolocation details.
All calculations run locally in your browser on Utilitoo. No data is sent to any server. Free and instant for network admins, cloud engineers, and developers.
CIDR Calculator turns slash notation into network details: masks, broadcast, usable hosts, and ranges. It speeds cloud and datacenter planning without a spreadsheet of binary conversions.
Common use cases
- Expanding 10.0.0.0/16 into network, broadcast, and host ranges for VPC planning.
- Checking whether an IP falls inside a firewall allow list CIDR.
- Studying for networking exams with instant prefix math.
- Documenting Docker and Kubernetes cluster ranges for teammates.
- Comparing two CIDR blocks before peering or routing changes.
Tips & common mistakes
IPv4 CIDR math is local in the browser - paste carefully to avoid typos in production ACLs. Pair with Subnet Calculator when you need to split a parent prefix. Verify critical changes in a lab VPC first. Write the parent prefix, mask, and first usable host into your runbook when documenting a change. Double-check that automation templates use the same CIDR string you calculated. For splits and VLSM practice, continue with Subnet Calculator on Utilitoo.
Common errors
- Using /24 habits on a /28 and expecting hundreds of hosts.
- Confusing network address with the first usable host in documentation.
How to use
- Enter CIDR notation.
- Click Calculate.
- Review network details.
Frequently Asked Questions
What is CIDR notation?▼
CIDR combines an IP address with a prefix length, like 192.168.1.0/24, defining a network block.
Does this support IPv6?▼
This calculator currently supports IPv4 CIDR blocks only.
What is a wildcard mask?▼
The inverse of the subnet mask, used in ACLs and routing configurations.
How are usable hosts calculated?▼
Total addresses minus network and broadcast addresses. /31 and /32 have special cases shown in results.
Is calculation done locally?▼
Yes. All CIDR math runs in your browser on Utilitoo.
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