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Subnet Calculator

Compute subnet masks, network/broadcast addresses, and usable host ranges from any CIDR. Plan a /24 office network correctly — local math, free, no signup.

100% Local Browser Native

How to Use the Subnet Calculator

1. Enter IP and CIDR

Address with prefix length.

2. Read the subnet

Mask, network, broadcast, and host range.

3. Plan DHCP

Scope usable hosts excluding both reserved ends.

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Frequently Asked Questions

How many hosts in a /24?

254 usable (256 minus network and broadcast). A /24 fits one office floor; /23 doubles it to 510 for growth.

Network vs broadcast address?

First address identifies the subnet, last is broadcast — neither assigns to hosts. The tool marks both so DHCP scopes start correctly.

CIDR to mask conversion?

/24 is 255.255.255.0, /16 is 255.255.0.0 — each bit adds doubling. Enter either form; both display.

Do subnet plans upload anywhere?

No — math runs locally in your browser. Nothing leaves your device.

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Last updated October 2026