CIDR / Subnet Calculator

Calculate the network address, broadcast address, and usable host range from a CIDR block. A /24 block gives 256 total addresses (254 usable), while a /26 gives 64 addresses (62 usable).

IP Address

CIDR Prefix (/0–32)

Tip: pasting a full block like 192.168.1.0/24 into the IP field splits it automatically.

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Why use CIDR / Subnet Calculator?

CIDR notation compresses a network's address and its size into one compact form (like 192.168.1.0/24), but reading the actual usable range from it requires binary math that's easy to get wrong by hand — how many host bits remain, where the network and broadcast addresses fall, and how many addresses that leaves for actual devices. This calculator does that math directly: enter a CIDR block and get the network address, broadcast address, full usable host range, and both total and usable host counts (always two less than the total, since the network and broadcast addresses are reserved) — useful for planning subnets, verifying a network configuration, or just checking how much room a given block provides.

Key benefits

Instant network/broadcast/host range calculation
Shows total and usable host counts
No manual binary math required
Free, unlimited use

Features

Network and broadcast address calculation
Usable host range
Subnet mask and total/usable host counts

Popular use cases

Planning IP address allocation for a subnet
Checking how many usable hosts a given CIDR block provides
Verifying a subnet's range before configuring network equipment
Learning or teaching subnetting

How to use CIDR / Subnet Calculator

1
Enter a CIDR block
Like 192.168.1.0/24.
2
Calculate
Network, broadcast, and usable range computed instantly.
3
Read the results
Including total and usable host counts.

Frequently asked questions

Why does a /24 subnet have only 254 usable addresses out of 256?

The first address in any subnet is reserved as the network address, and the last is reserved as the broadcast address — neither can be assigned to a host, so a /24 (256 total addresses) yields 254 usable host addresses.

What does the /24 or /26 number mean?

It's the number of bits used for the network portion of the address, out of 32 total bits in IPv4 — the remaining bits (32 minus the CIDR number) determine the subnet's size. A /24 leaves 8 bits for hosts (256 addresses), a /26 leaves 6 bits (64 addresses).

How is the broadcast address calculated?

It's the highest address in the subnet's range — all host bits set to 1. For 192.168.1.0/24, that's 192.168.1.255.

Last reviewed: August 2026

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