Subnet Mask Calculator
Calculate subnet mask, network address, broadcast address, number of hosts, and more from an IP address and CIDR prefix length.
Published by:
isCalculator Editorial Team
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How to use this tool?
This calculator computes key subnet details from an IP address and CIDR prefix.
- Enter IP Address – Type a valid IPv4 address (e.g.,
192.168.1.0). - Enter CIDR Prefix – Provide a number between
0and32(e.g.,24). - Click "Calculate" – The form validates inputs and displays results.
Outputs explained:
- Network Address – The subnet’s base address.
- Broadcast Address – The subnet’s broadcast address.
- Subnet Mask – Dotted decimal mask (e.g.,
255.255.255.0). - Number of Hosts – Usable hosts (2^(32-CIDR) – 2).
- First/Last Usable Host – Range for assigning to devices.
Note: For CIDR /31 or /32, host fields show "N/A" (no usable hosts).
Previous Results
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Frequently Asked Questions
A subnet mask is a 32-bit number that divides an IP address into network and host portions, used to identify the subnet to which a device belongs.
CIDR (Classless Inter-Domain Routing) notation is a compact representation of an IP address and its associated routing prefix, written as IP address followed by a slash and the prefix length (e.g., 192.168.1.0/24).
The number of usable hosts is 2^(32 - prefix length) - 2, subtracting the network and broadcast addresses.
