Subnet Calculator
Calculate IPv4 subnet details from an IP address and CIDR prefix. Get network/broadcast addresses, host range, wildcard mask, binary breakdown, and split subnets visually.
Subnet Calculator
Calculate network details from an IP address and subnet mask or CIDR notation.
| Field | Octet 1 | Octet 2 | Octet 3 | Octet 4 | Decimal |
|---|---|---|---|---|---|
| IP Address | 11000000 | 10101000 | 00000001 | 00000000 | 192.168.1.0 |
| Subnet Mask | 11111111 | 11111111 | 11111111 | 00000000 | 255.255.255.0 |
| Network | 11000000 | 10101000 | 00000001 | 00000000 | 192.168.1.0 |
| Broadcast | 11000000 | 10101000 | 00000001 | 11111111 | 192.168.1.255 |
Subnet Splitter
Split 192.168.1.0/24 into smaller subnets:
| # | Network | Range | Broadcast | Hosts |
|---|---|---|---|---|
| 1 | 192.168.1.0/25 | 192.168.1.1 - 192.168.1.126 | 192.168.1.127 | 126 |
| 2 | 192.168.1.128/25 | 192.168.1.129 - 192.168.1.254 | 192.168.1.255 | 126 |
Common Private Ranges
What is a Subnet Calculator?
A subnet calculator takes an IPv4 address and a subnet mask (or CIDR prefix length) and computes the full network details: network address, broadcast address, usable host range, wildcard mask, and more. It is essential for network engineers, sysadmins, and anyone studying for Cisco CCNA, CompTIA Network+, or similar certifications.
Key Features
- Full Subnet Details: Network address, broadcast, first/last host, total addresses, usable hosts, IP class, and type (private/public/loopback).
- Binary Breakdown: See every address in binary, octet by octet, with a visual mask showing network vs host bits.
- Subnet Splitter: Divide a network into smaller subnets by choosing a longer prefix. See all resulting subnets with their ranges.
- CIDR Support: Enter addresses in CIDR notation (e.g. 192.168.1.0/24) or select the prefix from a dropdown.
- Common Presets: One-click presets for RFC 1918 private ranges, loopback, and link-local networks.
- IPv6 Mapped: Shows the IPv4-mapped IPv6 address and hex notation.
How to use the Subnet Calculator
- Enter an IPv4 address (e.g. 192.168.1.0) or paste a CIDR block (e.g. 10.0.0.0/16).
- Select the subnet prefix length from the dropdown or quick-select buttons.
- Click Calculate to see all network details, binary breakdown, and mask visualization.
- Use the Subnet Splitter to divide the network into smaller subnets.
Understanding CIDR Notation
CIDR (Classless Inter-Domain Routing) notation appends a prefix length to an IP address, like 192.168.1.0/24. The prefix length indicates how many leading bits of the address identify the network. A /24 means 24 network bits and 8 host bits, giving 256 total addresses (254 usable hosts).
Subnet Mask Cheat Sheet (/8 to /32)
The table every network engineer keeps taped to a monitor. Usable hosts is total addresses minus the network and broadcast address.
| CIDR | Subnet mask | Usable hosts | Typical use |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 | Class A, 10.0.0.0/8 private range |
| /16 | 255.255.0.0 | 65,534 | Class B, 172.16.0.0/16, large sites |
| /22 | 255.255.252.0 | 1,022 | Campus or large office network |
| /23 | 255.255.254.0 | 510 | Two merged /24 networks |
| /24 | 255.255.255.0 | 254 | The standard LAN, 192.168.1.0/24 |
| /25 | 255.255.255.128 | 126 | Half a /24 |
| /26 | 255.255.255.192 | 62 | Quarter of a /24, small VLANs |
| /27 | 255.255.255.224 | 30 | Small office or device VLAN |
| /28 | 255.255.255.240 | 14 | Small cloud subnets, DMZ segments |
| /29 | 255.255.255.248 | 6 | ISP customer block, firewall segment |
| /30 | 255.255.255.252 | 2 | Router-to-router links |
| /31 | 255.255.255.254 | 2 | Point-to-point links (RFC 3021, no broadcast) |
| /32 | 255.255.255.255 | 1 | Single host route, loopbacks |
An online alternative to ipcalc
If you use ipcalc on Linux, this calculator covers the same job in the browser: the binary breakdown with network and host bits highlighted, wildcard masks for Cisco ACLs, and the subnet splitter for dividing a block into smaller networks. Everything runs client-side, so no addresses ever leave your machine, which matters when you are working with internal network plans.
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