IP Subnet Calculator
Calculate network address, broadcast, host range, and subnet mask from CIDR notation
What is the Subnet Calculator?
Subnetting divides a large network into smaller, more manageable pieces. Every network administrator, IT student, or anyone working toward a networking certification needs to understand it. Working out subnet masks, network addresses, broadcast addresses, and usable host ranges by hand is tedious and error-prone. CalciHub's subnet calculator takes an IP address and a subnet mask (or CIDR notation) and returns everything you need: network address, broadcast address, valid host range, and number of usable hosts.
How Does It Work?
An IP address is a 32-bit number. A subnet mask specifies which bits belong to the network and which belong to individual hosts. Applying the mask to an IP via a bitwise AND operation gives you the network address.
Network Address = IP AND Subnet Mask
Broadcast Address = Network Address OR (NOT Subnet Mask)
Usable Hosts = 2^(host bits) - 2
• Network Address: first address in the subnet (not assignable to a host)
• Broadcast Address: last address in the subnet (not assignable to a host)
• Usable Hosts: all addresses between network and broadcast
• Host bits: the number of bits set to 0 in the subnet mask
How to Use CalciHub's Subnet Calculator
1. Enter the IP address (e.g., 192.168.1.100).
2. Enter the subnet mask in dotted decimal (e.g., 255.255.255.0) or CIDR notation (e.g., /24).
3. Click Calculate.
4. Review the output: network address, broadcast, first/last usable host, and total host count.
Tip: /24 gives you 254 usable hosts, /25 gives 126, /26 gives 62. Each step up in CIDR prefix cuts the host count roughly in half, useful for quickly estimating what prefix you need.
A Quick Example
A network administrator needs to subnet the range 192.168.10.0 with a /26 mask.
• IP: 192.168.10.0
• Subnet: /26 = 255.255.255.192
• Network Address: 192.168.10.0
• Broadcast Address: 192.168.10.63
• First Usable Host: 192.168.10.1
• Last Usable Host: 192.168.10.62
• Total Usable Hosts: 62
That gives a segment of 62 usable IPs, enough for a department of 50 devices with a bit of room to grow.
Frequently Asked Questions
They describe the same thing in different formats. 255.255.255.0 and /24 are equivalent—/24 just counts the number of consecutive 1-bits in the mask (24 in this case). CIDR is shorter and more common in modern networking.
The first address in a subnet is the network address, and the last is the broadcast address. Neither can be assigned to a device, which is why usable hosts = 2^n - 2, not 2^n.
IPv6 uses the same CIDR prefix concept (/64 is the standard for most host segments), but the address space is 128-bit instead of 32-bit. Most subnet calculators handle IPv4 specifically; IPv6 subnetting uses similar logic but at a much larger scale.
A /32 subnet contains exactly one IP address – itself. It's used to identify a single host, often in routing tables or when defining loopback addresses. There are no 'other' hosts in a /32.
The reserved private ranges: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Home routers usually default to 192.168.0.0/24 or 192.168.1.0/24. Choosing a less common range such as 10.42.0.0/24 helps avoid clashes when connecting to a VPN that already uses the usual defaults.
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