Subnet Calculator
Online subnet calculator for CIDR and mask conversion, usable IP range calculation, and subnet planning
Network Input
Input Mode
Example: 192.168.1.0/24
Basic Info
Network Address
192.168.1.0
Broadcast Address
192.168.1.255
Subnet Mask
255.255.255.0
CIDR
192.168.1.0/24
Prefix Length
/24
IP Class
Class C
Host Info
Total Hosts
256
Usable Hosts
254
First Usable IP
192.168.1.1
Last Usable IP
192.168.1.254
Usable IP Range
192.168.1.1 - 192.168.1.254
Other Info
Wildcard Mask
0.0.0.255
Network Type
Small Network
Private Address
Yes
Binary View
Input IP (Binary)
11000000.10101000.00000001.00000000
Subnet Mask (Binary)
11111111.11111111.11111111.00000000
Network Address (Binary)
11000000.10101000.00000001.00000000
Subnet Calculation Guide
This tool supports CIDR and mask inputs, calculates network and broadcast addresses with usable host ranges, and provides subnet splitting plus VLSM planning for network design and troubleshooting.
Core Features
- Supports both CIDR notation and IP + subnet mask input modes.
- Calculates network address, broadcast address, usable hosts, and IP range instantly.
- Splits networks by subnet count and returns new prefix and each subnet range.
- Supports VLSM planning by host requirements for practical address allocation.
- Shows binary views of input IP, subnet mask, and network address for learning and debugging.
How to Use
- Choose CIDR mode or IP + subnet mask mode.
- Enter network parameters to get base network information in real time.
- For fixed-size split, enter subnet count and click Split Subnets.
- For variable-size planning, add host requirements and run VLSM calculation.
Calculation Rules
- A /32 network contains only one address and has 1 usable host.
- A /31 network is treated as point-to-point and has 2 usable addresses.
- For regular prefixes, usable hosts = total addresses - 2.
- VLSM sorts host requirements from large to small before allocation for better utilization.
FAQ
Why did I request 3 subnets but get 4?
Subnet counts must be powers of two, so 3 is rounded up to 4 to keep valid subnet boundaries.
Why can VLSM calculation fail?
Usually because one requirement is larger than the base network, or total requirements exceed available address space.
Will my network data be uploaded?
No. All calculations run locally in your browser without uploading your network inputs.