Online IPv4 Subnet Calculator
Calculate CIDR notations, subnet masks, network & broadcast boundaries, and usable host address ranges. 100% private in-browser calculator.
At a glance
IPv4 Subnet Calculator & CIDR Utility is a free web tool that calculates IPv4 subnet masks, CIDR prefixes, network boundaries, broadcast addresses, and usable host ranges with bitwise binary telemetry. It toggles between CIDR slash prefixes (/0 to /32) or dotted-quad subnet masks seamlessly. Your inputs never leave your device, and there is no sign-up or install.
100% In-Browser Network Computation
All 32-bit bitwise subnet arithmetic executes purely in your local browser memory. Zero corporate IP addresses or topology data are sent across the network.
CIDR Subnet Reference Table (/8 to /32)
| CIDR | Subnet Mask | Usable Hosts | Total IPs | Wildcard Mask | Action |
|---|
Core Capabilities
- Instant Bitwise Arithmetic: Calculates network, broadcast, wildcard, and usable host bounds on every keystroke.
- CIDR & Netmask Synchronization: Toggle between CIDR slash prefixes (/0 to /32) or dotted-quad subnet masks seamlessly.
- RFC Scope & Class Detection: Instantly detects RFC 1918 private scopes, loopbacks, link-local ranges, and Class A/B/C/D allocations.
- 100% Client-Side Privacy: Plan internal AWS/GCP VPCs, Kubernetes subnets, and corporate networks with zero telemetry.
How to Use
- 1 Enter IP Address: Type your target IPv4 address or pick a preset like Home LAN or Corporate VPC.
- 2 Select CIDR or Mask: Choose the subnet prefix length (/8 through /32) from the dropdown or matrix table.
- 3 Review & Copy: Copy individual values or the full formatted subnet summary to configure your firewall or routers.
Frequently Asked Questions
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation specifies an IP address along with its associated routing prefix length using a slash followed by a number (e.g., 192.168.1.0/24). The prefix number indicates how many leading bits of the 32-bit address represent the network identifier.
Why are there 2 fewer usable hosts than total IP addresses?
In standard IPv4 subnets (/30 and larger), the first address is reserved as the Network Identifier, and the last address is reserved as the Directed Broadcast Address. Devices cannot use either address as a normal host IP. For /31 point-to-point links (RFC 3021), both addresses are usable.
What is a Wildcard Mask?
A wildcard mask is the exact bitwise inverse of a subnet mask (255.255.255.255 minus the subnet mask). It is commonly used in Cisco IOS Access Control Lists (ACLs) and OSPF routing configurations to match ranges of IP addresses.
Why Use This IPv4 Subnet Calculator & CIDR Utility?
How to Use IPv4 Subnet Calculator & CIDR Utility
Enter IP Address
Type your target IPv4 address or pick a preset like Home LAN or Corporate VPC.
Select CIDR or Mask
Choose the subnet prefix length (/8 through /32) from the dropdown or matrix table.
Review & Copy
Copy individual values or the full formatted subnet summary to configure your firewall or routers.
Home LAN Breakdown: 192.168.1.100/24 Yields 254 Hosts
The engine parses the address into a 32-bit unsigned integer and derives mask, network, broadcast, and host bounds with bitwise arithmetic, fully client-side.
IP: 192.168.1.100, CIDR: /24 (mask 255.255.255.0)
Network: 192.168.1.0, Broadcast: 192.168.1.255. Usable: 192.168.1.1 - 192.168.1.254 (254 hosts).
Technical Specifications & Engine Details
| Specification | Details |
|---|---|
| Supported Formats | IPV4, CIDR, NETMASK → NETWORK-TELEMETRY, HOST-RANGE, BINARY-MASKS |
| Execution Mode | 100% Client-Side In-Browser (client) |
| Browser Requirements | Requires modern web browser with ECMAScript 6+ and standard DOM Web APIs. |
| Performance Constraints | Client browser memory limit (typically 1–2 GB RAM); processing speed depends on local device CPU. |
100% Client-Side Privacy Guarantee
All IPv4 subnet and bitwise calculations execute purely in your local browser memory. Zero IP addresses or network topologies are transmitted to external servers.
Frequently Asked Questions
What is CIDR notation?
Why are there 2 fewer usable hosts than total IP addresses?
What is a Wildcard Mask?
Methodology
Rankings and recommendations here are never paid for.
Last updated .