CIDR Calculator — IPv4 Subnet & Network Range Mapper
Calculate subnet ranges, usable host counts, broadcast addresses, and subnet masks from CIDR notation. Shows network and host addresses in both decimal and binary with color-coded bit visualization.
How to Use CIDR Calculator — IPv4 Subnet & Network Range Mapper
How to Use the CIDR Subnet Calculator
Step 1: Enter a CIDR Address
Type or paste a CIDR notation address into the input field. The format is:
IP address / prefix length
For example:
192.168.1.0/24— a typical home or office LAN10.0.0.0/8— a large Class A private network10.10.5.0/27— a small subnet with 30 usable hosts
Step 2: Read the Results
The results grid shows:
| Field | Description |
|---|---|
| Network Address | The first address in the block (not routable to hosts) |
| Broadcast Address | The last address (packets sent here reach all hosts) |
| First Usable Host | Lowest IP you can assign to a device |
| Last Usable Host | Highest IP you can assign to a device |
| Subnet Mask | Decimal form, e.g. 255.255.255.0 for /24 |
| Wildcard Mask | Inverse of the subnet mask, used in ACLs |
| Usable Hosts | Total addresses minus network and broadcast |
| Total IPs | Full address count including network and broadcast |
Step 3: Read the Binary Visualisation
The binary table shows each address in dotted binary notation. Bits are colour-coded:
- Indigo (blue) — network bits, set by the prefix length
- Orange — host bits, available for device addressing
This makes it easy to see why the network address has all host bits set to 0 and the broadcast has all host bits set to 1.
Step 4: Use the Examples
Click any example button to load a common subnet for quick reference:
192.168.1.0/24— standard 254-host LAN10.0.0.0/8— Class A private (16 million hosts)10.10.5.0/27— small 30-host subnet0.0.0.0/0— the default route (entire IPv4 internet)
Frequently Asked Questions
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