Subnet Calculator
Calculate IPv4 subnets. Enter an IP address and CIDR or subnet mask to find the network address, broadcast address, and usable host range.
Calculation Result
Details
Binary Representation
📖 How to Use
- Enter an IP address (e.g., 192.168.1.100)
- Enter CIDR notation or subnet mask
- Use quick preset buttons for common CIDR values
- Review network information in the calculation results
- Use the CIDR Converter tab to convert between CIDR and subnet mask
- Use the Subnet Divider tab to split large networks into smaller subnets
✨ Features
- ✓IPv4 subnet calculation
- ✓CIDR ↔ Subnet mask conversion
- ✓Network/Broadcast address calculation
- ✓Usable host range display
- ✓Subnet division calculation
- ✓Automatic private IP detection
- ✓Binary representation view
- ✓CIDR reference table
📐 Formula
Network Address = IP AND Subnet Mask
Broadcast = Network Address OR Wildcard Mask
Usable Hosts = 2^(32-CIDR) - 2💡 How It Works
- •Subnetting is the technique of dividing a large network into smaller networks.
- •CIDR (Classless Inter-Domain Routing) uses slash notation like /24 to indicate network bits.
- •Subnet mask uses 1s for network portion and 0s for host portion, like 255.255.255.0.
- •Wildcard mask is the inverse of subnet mask, used in ACLs and routing.
- •Network address has all host bits set to 0, representing the network itself.
- •Broadcast address has all host bits set to 1, used to send to all hosts in the network.
- •Usable hosts equals total addresses minus network and broadcast addresses.
❓ FAQ
Q. What's the difference between /24 and 255.255.255.0?
A. They're the same thing. /24 is CIDR notation meaning 24 network bits, while 255.255.255.0 expresses the same as a subnet mask.
Q. What's the difference between private and public IP?
A. Private IPs (10.x.x.x, 172.16-31.x.x, 192.168.x.x) are for internal networks only. Public IPs are globally unique addresses on the internet.
Q. Why are there 2 fewer usable hosts than total addresses?
A. The network address (first) and broadcast address (last) cannot be assigned to hosts. However, /31 and /32 are exceptions.
Q. When should I use subnet division?
A. When splitting a large network by department, floor, or purpose. It helps with security, broadcast domain reduction, and IP management.
Q. When is a /31 subnet used?
A. For point-to-point links between routers. Per RFC 3021, both addresses in a /31 can be assigned to hosts.