IPv4 Subnet Calculator
Free IPv4 subnet calculator and CIDR calculator. Convert CIDR to subnet mask, broadcast address, network address, IP range, wildcard mask, and usable hosts. Handles /31 and /32.
IPv4 CIDR
Enter an IPv4 address and prefix, for example 10.0.0.50/28.
Network address
192.168.1.0
Broadcast address
192.168.1.255
Subnet mask
255.255.255.0
Wildcard mask
0.0.0.255
Total addresses
256
Usable host addresses
254
First usable host
192.168.1.1
Last usable host
192.168.1.254
CIDR prefix
/24
| Network address | 192.168.1.0 |
|---|---|
| Broadcast address | 192.168.1.255 |
| Subnet mask | 255.255.255.0 |
| Wildcard mask | 0.0.0.255 |
| Total addresses | 256 |
| Usable host addresses | 254 |
| First usable host | 192.168.1.1 |
| Last usable host | 192.168.1.254 |
| CIDR prefix | /24 |
This IPv4 subnet calculator converts CIDR notation into the subnet mask, broadcast address, network address, IP range, wildcard mask, and usable host count. Use it as a CIDR calculator, subnet mask calculator, broadcast address calculator, or quick IP subnet calculator for routing, firewall rules, classroom exercises, and day-to-day network operations. It also handles /31 point-to-point links (RFC 3021) and /32 host routes. Everything runs in your browser for fast, private calculations.
How to Use IPv4 Subnet Calculator
Enter CIDR notation
Type an IPv4 address, a slash, and a prefix length (0–32), for example 192.168.1.10/24 or 10.0.0.0/28. The calculator instantly converts CIDR to subnet mask, network address, broadcast address, and usable hosts. Use the copy buttons beside each value when you need to paste into configs, IP plans, or docs.
Read usable hosts
For most prefixes between /1 and /30, the network and broadcast addresses are reserved, so usable hosts are total addresses minus two. /31 is special: both addresses may be used on point-to-point links. /32 is a single-host route.
Use wildcard masks
The wildcard mask is the bitwise inverse of the subnet mask (within 32 bits). It appears in Cisco ACLs and some firewall patterns. If you searched for a wildcard mask calculator or CIDR to subnet mask converter, this row is the quick reference you usually need.
Treat /0 as educational
A /0 block spans all of IPv4. The math is shown for learning; real designs use sensible boundaries and routing policies instead of a single giant flat network.
Calculator Features
Full IPv4 breakdown
Network address, broadcast address, subnet mask, IP range, totals, and first/last usable host.
RFC 3021 /31
Point-to-point /31 handling with a clear on-page note.
/32 host routes
Single-address prefixes show network and host as the same value.
Copy-friendly rows
Copy each result quickly without selecting text by hand.
Private by design
Calculations stay in your browser; nothing is uploaded.
Responsive layout
Works on desktop and mobile for troubleshooting on the go.
Complete Function List
- CIDR parsing (address/prefix):
- Network and broadcast addresses:
- Subnet mask (dotted decimal):
- CIDR to subnet mask conversion:
- Wildcard mask (dotted decimal):
- IP range calculation:
- Total addresses in subnet:
- Usable host count with /31 and /32 rules:
- First and last usable host:
- Copy buttons for outputs:
- /0 warning for unrealistic designs:
- Client-side only processing:
Common Calculations & Examples
Example 1: Typical home LAN (/24)
Problem: You have 192.168.1.50/24 and need the subnet boundaries.
Steps:
- Enter 192.168.1.50/24 in the CIDR field
- Read the network and broadcast rows
Explanation: /24 is one of the most common searches because it is a standard LAN-sized subnet with 256 total addresses and 254 usable hosts.
Example 2: How many usable hosts in a /27?
Problem: You need to know the usable host count for 192.168.10.33/27.
Steps:
- Enter 192.168.10.33/27
- Check the usable host count and range rows
Explanation: This is a common long-tail subnetting query for admins splitting a /24 into smaller networks.
Example 3: CIDR to subnet mask (/28)
Problem: You need to convert /28 into a dotted subnet mask and IP range.
Steps:
- Enter an address such as 10.0.0.50/28
- Read the subnet mask, network address, and last usable rows
Explanation: This targets the common task of turning CIDR notation into a classic dotted-decimal subnet mask.
Example 4: Small point-to-point (/30)
Problem: A link uses 10.0.0.0/30—what are the usable router addresses?
Steps:
- Enter 10.0.0.0/30
- Check first and last usable host
Explanation: /30 gives four addresses: network, two usable hosts, and broadcast.
Example 5: Modern /31 link
Problem: Your template uses 10.10.10.0/31 between two routers.
Steps:
- Enter 10.10.10.0/31
- Read the RFC 3021 note and usable count
Explanation: /31 saves address space compared to /30 when broadcast is not needed.