Subnet Calculator
Calculate network subnet details including network address, broadcast address, usable host range, and subnet mask from an IP address and CIDR prefix.
Published by:
isCalculator Editorial Team
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How to use this tool?
This subnet calculator computes key network details from an IP address and CIDR prefix.
- Enter an IPv4 address (e.g.,
192.168.1.0) in the IP Address field. - Enter a CIDR prefix (e.g.,
24) between 0 and 32 in the CIDR Prefix field. - Click Calculate or press Enter in either input field.
- Review the results:
- Network Address – the first address in the subnet.
- Broadcast Address – the last address in the subnet.
- Usable Hosts – number of assignable IPs (total minus network and broadcast).
- Subnet Mask – dotted decimal mask and its CIDR notation.
- Usable Host Range – the range of IPs available for devices.
- Check the Formula Breakdown section for a step-by-step explanation of the calculations.
Note: The calculator expects standard IPv4 addresses (e.g., 192.168.1.0) and a CIDR value from 0 to 32. For /31 (point-to-point) or /32 (single host), host range and usable host count adjust accordingly.
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 parts. It is used to identify which part of an IP address is the network and which part is the host.
CIDR (Classless Inter-Domain Routing) notation is a compact way to specify an IP address and its subnet mask, e.g., 192.168.1.0/24. The number after the slash is the prefix length, indicating how many bits are used for the network portion.
A /24 subnet has 256 total addresses, but the network address and broadcast address are reserved, leaving 254 usable host addresses.