# IP subnet calculator

> Subnet calculator for IPv4 and IPv6: CIDR to range, split into subnets, aggregate ranges and convert notations. Runs in your browser.

CIDR blocks, ranges, splits and conversions for IPv4 and IPv6.

## About the calculator

Enter an IPv4 or IPv6 address with a CIDR prefix, or a range, to get the network and broadcast address, netmask, wildcard mask, first and last usable host and the number of addresses. Drag the prefix slider or toggle bits directly to see how the subnet changes.

Split a block into equal subnets, aggregate a list of ranges into the fewest CIDR blocks, and convert between dotted-decimal, binary, hexadecimal and integer notation. Everything runs in your browser; nothing is sent to a server.

### What does /24 mean?

The number after the slash is the prefix length: how many leading bits of the address name the network. A /24 fixes 24 of 32 bits, leaving 8 for hosts, so it holds 256 addresses, 192.168.1.0 to 192.168.1.255. A smaller number is a larger network: a /16 holds 65,536 addresses, a /8 over sixteen million.

### How many usable hosts does a subnet have?

For IPv4, two to the power of the host bits minus two, because the first address names the network and the last is the broadcast: a /24 has 254 usable hosts, a /29 has 6. The exceptions are /31, used on point-to-point links with both addresses usable, and /32, a single host. IPv6 has no broadcast address, so every address in a block is usable.

### How do I split a network into subnets?

Enter the block and choose the number of subnets or the prefix length you want. Each extra bit of prefix halves the block: a /24 splits into two /25, four /26 or eight /27. The calculator lists every subnet with its range and usable hosts, and the same works for IPv6, where a /48 is commonly split into /64 networks.

### What is CIDR aggregation?

Combining several ranges into the fewest blocks that cover exactly the same addresses, also called supernetting. Two adjacent /25 networks become one /24; a range that starts or ends mid-block needs several blocks of different sizes. Paste a list of ranges or CIDR blocks and the tool merges what it can.

### Does IPv6 have a broadcast address or a netmask?

No. IPv6 uses multicast for what broadcast did, and networks are written only with a prefix length. The standard size for a LAN is a /64, which leaves 64 bits for the interface identifier; ISPs typically delegate a /56 or /48 to a customer, and the calculator shows how many /64 networks fit into either.

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Canonical page: https://ip-tools.eu/calc · API documentation: https://ip-tools.eu/docs/api.md · All pages: https://ip-tools.eu/llms.txt