🌐 Subnet Calculator

IPv4 / CIDR network calculator with a plain-English networking guide — by Dinal Studios

🧮 Calculate a Subnet INSTANT

Enter any IPv4 address and choose the CIDR prefix length (or pick a subnet mask). Results update as you type.

Network address—
Broadcast address—
Subnet mask—
Wildcard mask—
First usable host—
Last usable host—
Total addresses—
Usable hosts—
IP type—
IP in binary—
Network in binary—

📊 Quick Reference — Common Prefixes

CIDRSubnet maskTotal addressesUsable hostsTypical use
/8255.0.0.016,777,21616,777,214Huge private networks (10.x)
/16255.255.0.065,53665,534Large campus / cloud VPC
/24255.255.255.0256254Home & small office LAN
/26255.255.255.1926462Small department subnet
/30255.255.255.25242Router-to-router links
/32255.255.255.25511Single host route

🎓 Networking Basics — Subnets in Plain English

IP address = street address for a device. An IPv4 address like 192.168.1.10 is 32 bits written as four decimal numbers (octets), each 0–255.
CIDR / subnet mask = where the street ends. The prefix (e.g. /24) says how many of the 32 bits identify the network. The rest identify individual hosts on that network. Bigger prefix = smaller network.
Network & broadcast are reserved. The first address of a subnet names the network itself; the last is the broadcast address used to talk to everyone at once. That's why usable hosts = total − 2.
Why subnet at all? Splitting one big network into subnets limits broadcast traffic, improves performance, and adds security — a guest Wi-Fi subnet can be kept away from office file servers, for example.
Private vs public ranges. 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 are private — free for anyone to use inside their own network, and not reachable from the internet directly.
The one formula to remember. Hosts = 2(32 − prefix). A /24 leaves 8 host bits → 2⁸ = 256 addresses, 254 usable. Each step up in prefix halves the network; each step down doubles it.

🔒 100% private: all calculations happen on your device.

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