Network tool
IPv4 Network & Subnet Calculator
A privacy-first IPv4 networking workbench for subnet calculations, mask conversion, host/network identification and IPv4 number conversion. All calculations run locally in your browser.
Privacy:
All calculations are performed locally in your browser.
No IP address or calculation data is sent to Koevn servers.
IPv4 workbench
Choose calculation
Network and IP calculator
Find a subnet boundary, host range, masks and address counts from an IPv4 address and prefix.
Result
- Canonical CIDR
- Network address
- Broadcast address
- First usable address
- Last usable address
- Subnet mask
- Wildcard mask
- Total addresses
- Usable addresses
Prefix to subnet mask converter
Convert a CIDR prefix to decimal, hexadecimal and binary masks.
Result
- Decimal mask
- Hexadecimal mask
- Binary mask
- Wildcard mask
Network / host calculator
Split an IPv4 address into its network and host portions using a contiguous subnet mask.
Result
- Network address
- Host / node portion
- Broadcast address
- CIDR
Subnet mask to wildcard converter
Convert a valid contiguous subnet mask to its wildcard mask.
Result
- Wildcard mask
Subnet mask to prefix converter
Validate a contiguous subnet mask and return its CIDR prefix and binary form.
Result
- Prefix length
- CIDR
- Binary mask
IPv4 bitwise NOT calculator
Invert any valid IPv4 address octet by octet. Unlike wildcard conversion, the input does not need to be a subnet mask.
Result
- Bitwise complement
Prefix and address count calculator
Calculate total and usable address counts, masks, and network/host bit lengths.
Result
- Usable addresses
- Total addresses
- Subnet mask
- Wildcard mask
- Network bits
- Host bits
TCP/IP base converter
Use any one field as the source. The other three representations update locally after input, blur or Enter.
Understanding IPv4 subnet calculations
IPv4 subnet calculation separates a 32-bit address into network and host portions. The workbench applies the selected prefix or contiguous mask to derive the network boundary, broadcast address, usable range and alternative number representations.
How subnet masks work
A contiguous subnet mask uses leading one bits for the network and trailing zero bits for hosts. Non-contiguous masks are rejected.
CIDR and address count
A /n prefix reserves n network bits. Total addresses equal 2 raised to the remaining host-bit count.
What is a wildcard mask?
A wildcard mask is the bitwise inverse of a valid subnet mask and is commonly used in network matching rules.
/31 point-to-point networks
RFC 3021 treats both addresses in a /31 as usable point-to-point endpoints; the traditional network and broadcast exclusions do not apply.
/32 host routes
A /32 identifies one address. Its network, broadcast, first and last usable values are all that same address.
IPv4 number representations
The same 32 bits can be written as dotted decimal, dotted or compact binary, an unsigned decimal integer, or hexadecimal octets.
Common CIDR reference table
| Prefix | Subnet mask | Total | Usable |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 | 16,777,214 |
| /16 | 255.255.0.0 | 65,536 | 65,534 |
| /20 | 255.255.240.0 | 4,096 | 4,094 |
| /21 | 255.255.248.0 | 2,048 | 2,046 |
| /22 | 255.255.252.0 | 1,024 | 1,022 |
| /23 | 255.255.254.0 | 512 | 510 |
| /24 | 255.255.255.0 | 256 | 254 |
| /25 | 255.255.255.128 | 128 | 126 |
| /26 | 255.255.255.192 | 64 | 62 |
| /27 | 255.255.255.224 | 32 | 30 |
| /28 | 255.255.255.240 | 16 | 14 |
| /29 | 255.255.255.248 | 8 | 6 |
| /30 | 255.255.255.252 | 4 | 2 |
| /31 | 255.255.255.254 | 2 | 2 |
| /32 | 255.255.255.255 | 1 | 1 |
Usable counts follow conventional network/broadcast exclusions through /30, RFC 3021 semantics for /31, and single-host semantics for /32.
How the calculation works
- Validate four decimal IPv4 octets and a prefix between 0 and 32.
- Build the 32-bit subnet mask from the prefix and invert it for the wildcard mask.
- Apply the subnet mask to find the network, then combine the network with the wildcard to find the broadcast.
- Calculate counts and usable endpoints according to conventional, /31, or /32 rules.
All operations use a bundled, deterministic IPv4 module. The page has no tool API endpoint and sends no calculator input to a third party.
CIDR examples
- 192.168.10.100/24 belongs to 192.168.10.0/24, with 254 conventionally usable host addresses.
- 198.51.100.9/31 is the point-to-point block 198.51.100.8/31; both endpoints are usable under RFC 3021.
- 203.0.113.7/32 represents one host route and one usable address.