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IPv4 Subnet & CIDR Calculator
Calculate network addresses, broadcast addresses, subnet masks, usable host IP ranges, and binary forms for IPv4 subnets.
IPv4 Subnet & CIDR Calculator: TOEA computes bitwise network masks, wildcard masks, broadcast limits, and host ranges for standard classful and CIDR IPv4 subnets. Runs 100% locally in your browser with zero server file uploads.
- Category
- Developer tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
Subnet Details
| IP Address | 192.168.1.100 |
| Subnet Mask | 255.255.255.0 |
| Wildcard Mask | 0.0.0.255 |
| Network Address | 192.168.1.0 |
| Broadcast Address | 192.168.1.255 |
| First Usable Host | 192.168.1.1 |
| Last Usable Host | 192.168.1.254 |
| Total Addresses | 256 |
| IP Binary | 11000000.10101000.00000001.01100100 |
| Mask Binary | 11111111.11111111.11111111.00000000 |
Sizing a subnet
Each prefix step halves the block. A /24 has 254 usable addresses, /25 has 126, /26 has 62, /27 has 30, /28 has 14, /29 has 6, and /30 has 2. Cloud networks take more: AWS and Azure each reserve five addresses in every subnet, so a /28 there leaves 11 for your machines. Plan for growth, since resizing a subnet in use usually means moving everything in it.
The /31 and /32 prefixes
A /31 has no separate network and broadcast addresses: RFC 3021 lets both addresses be used on a point-to-point link between two routers, which is why the calculator shows 2 usable hosts rather than 0. A /32 names exactly one address and is used for host routes, loopback addresses, and allow-lists that admit a single machine.
Private and special ranges
The private ranges from RFC 1918 are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16; the calculator also marks the 127.0.0.0/8 loopback range. Two more are easy to mistake for public addresses: 100.64.0.0/10 is shared space that carrier-grade NAT uses, and 169.254.0.0/16 is what a device assigns itself when it gets no address from DHCP. Seeing a 169.254 address usually means the network setup failed.
How to use it
- Enter an IPv4 address and CIDR prefix (e.g. 192.168.1.100/24).
- Review network details, usable IP range, host counts, and binary masks.
- Copy the summary or IP details for network configuration.
Privacy & limitations
All IP address and subnet math runs entirely inside local browser JavaScript memory.
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Frequently asked questions
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) specifies the number of leading 1-bits in the subnet mask, such as /24 for 255.255.255.0.
Why are 2 addresses subtracted for usable hosts?
The network address (all host bits 0) and broadcast address (all host bits 1) are reserved in standard IPv4 subnets.
Free tool · runs in your browser · no account required