IPv4 and IPv6 CIDR: network, broadcast, host range, mask, wildcard and subnet splits
Runs in your browser. Nothing you type is sent anywhere. Updated on 25 Oct 2026.A subnet calculator turns an address and prefix into its network, broadcast and usable host range. For 192.168.10.77/26 the network is 192.168.10.64, the broadcast is 192.168.10.127, and 62 hosts run from .65 to .126. A /31 keeps both addresses as hosts, per RFC 3021.
Type an address with a prefix, such as 192.168.1.0/24, or with a dotted mask, in Address / prefix.
Read the network, subnet mask, wildcard mask, first and last host, broadcast and usable hosts.
Turn on Binary to see the address and mask bit by bit.
Under Split into subnets, choose a New prefix or type Hosts needed, then copy or download the list.
This subnet calculator takes an IPv4 or IPv6 address with a prefix and shows everything that follows from it. For IPv4 you get the network address, broadcast address, first and last usable host, the number of hosts, the subnet mask, the wildcard mask used by Cisco access lists and OSPF, the address as hex and as a 32-bit integer, and a binary view where the network bits and host bits are split so you can see exactly where the boundary falls.
You can type the prefix as /26 or give a dotted mask such as 255.255.255.192 after the address. A bare address is read as a /32. The split panel divides the network into equal smaller subnets, for example a /24 into four /26 blocks, and lists each block's range. A host-count box suggests the smallest prefix that still fits that many machines.
Two cases are handled as the standards say rather than by the usual formula. A /31 has no network or broadcast address: RFC 3021 lets both addresses be hosts on a point-to-point link, so it shows 2 hosts. A /32 is a single address. The page also names special ranges: RFC 1918 private blocks, carrier-grade NAT (100.64.0.0/10), link-local, loopback, multicast and the documentation ranges.
For IPv6 the calculator shows the network, the first and last address in the canonical RFC 5952 form, the network also fully expanded, the size as a power of two, and how many /64 subnets fit inside.
What it does not do: variable-length subnet planning across several sizes, route summarisation, or looking up who owns an address. Everything runs in your browser; nothing you type is sent anywhere. Related tools: Number Base Converter, URL Parser.
A /24 has 256 addresses. The first is the network address and the last is the broadcast address, so 254 remain for hosts. The general rule is 2 to the power of (32 minus the prefix), minus 2, which gives 62 for a /26 and 14 for a /28.
RFC 3021 allows a /31 on point-to-point links, where a network or broadcast address is pointless. Both addresses become hosts, which saves half the addresses on router links. The usual formula would give zero, so the calculator follows the RFC and shows no broadcast address for /31 or /32.
A wildcard mask is the subnet mask with every bit flipped: 255.255.255.192 becomes 0.0.0.63. Cisco access lists and OSPF network statements use it, where a 0 bit means the address must match and a 1 bit means any value is accepted.
Yes. Type the address, a space, then the dotted mask, such as 192.168.1.130 255.255.255.128, and the calculator converts it to /25. A mask whose 1 bits are not all at the front, such as 255.0.255.0, is rejected with a message, because no prefix length matches it.
Pick a longer prefix in the split panel. A /24 split into /26 gives four blocks of 64 addresses: .0, .64, .128 and .192, each with 62 hosts. Up to 256 blocks are listed with their ranges; the total count is always shown, even when the list is cut short.
IPv6 prefixes are huge: a /64 alone holds 2^64 addresses, about 18 quintillion. A power of two is easier to compare than a 20-digit number, so the page shows 2^(128 minus the prefix), the exact figure beneath it, and how many /64 networks the prefix contains.
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Also works as: CIDR Calculator.