IPv4 subnet sizes are determined by the CIDR prefix. A /29 contains 8 total addresses and 6 usable host addresses, a /28 contains 16 and 14, and a /27 contains 32 and 30. Use the complete /8–/32 table or enter any IPv4 CIDR in the calculator to find its subnet mask, network address, broadcast address, and usable range.
IPv4 subnet size and usable IP address table
For conventional IPv4 subnets from /8 through /30, usable host addresses equal the total minus the network and broadcast addresses. A /31 is a special point-to-point prefix under RFC 3021, while a /32 identifies one host route.
| Prefix | Subnet mask | Total IPs | Usable hosts | Typical use |
|---|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 | 16,777,214 | Very large network allocation |
| /9 | 255.128.0.0 | 8,388,608 | 8,388,606 | Half of a /8 network |
| /10 | 255.192.0.0 | 4,194,304 | 4,194,302 | Large private or provider block |
| /11 | 255.224.0.0 | 2,097,152 | 2,097,150 | Very large provider allocation |
| /12 | 255.240.0.0 | 1,048,576 | 1,048,574 | Private 172.16.0.0 range size |
| /13 | 255.248.0.0 | 524,288 | 524,286 | Large provider allocation |
| /14 | 255.252.0.0 | 262,144 | 262,142 | Large provider allocation |
| /15 | 255.254.0.0 | 131,072 | 131,070 | Two contiguous /16 networks |
| /16 | 255.255.0.0 | 65,536 | 65,534 | Large private or public network |
| /17 | 255.255.128.0 | 32,768 | 32,766 | Large enterprise allocation |
| /18 | 255.255.192.0 | 16,384 | 16,382 | Regional infrastructure allocation |
| /19 | 255.255.224.0 | 8,192 | 8,190 | Medium infrastructure allocation |
| /20 | 255.255.240.0 | 4,096 | 4,094 | Small hosting or campus allocation |
| /21 | 255.255.248.0 | 2,048 | 2,046 | Eight contiguous /24 networks |
| /22 | 255.255.252.0 | 1,024 | 1,022 | Four contiguous /24 networks |
| /23 | 255.255.254.0 | 512 | 510 | Two contiguous /24 networks |
| /24 | 255.255.255.0 | 256 | 254 | Standard small LAN or server network |
| /25 | 255.255.255.128 | 128 | 126 | Half of a /24 network |
| /26 | 255.255.255.192 | 64 | 62 | Department or medium service pool |
| /27 | 255.255.255.224 | 32 | 30 | Larger VPS, proxy, or mail pool |
| /28 | 255.255.255.240 | 16 | 14 | Small application or customer pool |
| /29 | 255.255.255.248 | 8 | 6 | Small routed block or service pool |
| /30 | 255.255.255.252 | 4 | 2 | Traditional point-to-point link |
| /31 | 255.255.255.254 | 2 | 2* | Point-to-point link (RFC 3021) |
| /32 | 255.255.255.255 | 1 | 1* | Single host route |
* /31 and /32 are special routing cases rather than conventional multi-host subnets. On a /31 point-to-point link both endpoint addresses are usable; a /32 represents exactly one address.
IPv4 CIDR subnet calculator
Enter an IPv4 address with its prefix, such as 192.0.2.40/29. The calculator runs in your browser and does not send the address anywhere.
Usable hosts versus customer-assignable IPs
The table uses the standard host count: total addresses minus network and broadcast for /8–/30. In an on-link configuration, a router may consume one of those usable host addresses as the gateway. A routed block avoids that extra allocation because the next hop is the VPS main IP outside the block. TinyServers therefore makes all 6 host addresses in a routed /29, all 14 in a /28, and all 30 in a /27 available for configuration on the server.
/32 subnet: 1 IP address
A /32 uses mask 255.255.255.255 and identifies one exact IPv4 address. It is normally used as a host route, loopback, or routed service address.
/31 subnet: 2 endpoint addresses
A /31 uses mask 255.255.255.254. RFC 3021 permits both addresses on a point-to-point link, where separate network and broadcast addresses are unnecessary.
/30 subnet: 4 total, 2 usable IPs
A /30 subnet mask is 255.255.255.252. It has 4 total addresses and 2 usable host addresses, which made /30 the traditional choice for point-to-point links.
/29 subnet: 8 total, 6 usable IPs
A /29 subnet mask is 255.255.255.248. It provides 8 total addresses and 6 usable host addresses. For a small pool attached to a VPS, see the TinyServers routed /29 IPv4 add-on.
/28 subnet: 16 total, 14 usable IPs
A /28 subnet mask is 255.255.255.240. It provides 16 total addresses and 14 usable host addresses. The routed /28 IPv4 add-on suits larger service, VM, or customer pools.
/27 subnet: 32 total, 30 usable IPs
A /27 subnet mask is 255.255.255.224. It provides 32 total addresses and 30 usable host addresses. For a larger VPS address pool, see the TinyServers routed /27 IPv4 add-on.
/26 subnet: 64 total, 62 usable IPs
A /26 uses mask 255.255.255.192 and divides a /24 into four equal blocks. Each block has 64 total addresses and 62 conventional host addresses.
/25 subnet: 128 total, 126 usable IPs
A /25 uses mask 255.255.255.128 and divides a /24 into two halves. Each half contains 128 total addresses and 126 usable host addresses.
/24 subnet: 256 total, 254 usable IPs
A /24 uses mask 255.255.255.0. It is the familiar 256-address block with 254 conventional host addresses.
/23 subnet: 512 total, 510 usable IPs
A /23 uses mask 255.255.254.0 and combines two contiguous /24 blocks, giving 512 total addresses and 510 usable hosts.
/22 subnet: 1,024 total, 1,022 usable IPs
A /22 uses mask 255.255.252.0 and combines four contiguous /24 blocks.
/21 subnet: 2,048 total, 2,046 usable IPs
A /21 uses mask 255.255.248.0 and combines eight contiguous /24 blocks.
/20 subnet: 4,096 total, 4,094 usable IPs
A /20 uses mask 255.255.240.0 and is often large enough for a campus or hosting allocation.
/19 subnet: 8,192 total, 8,190 usable IPs
A /19 uses mask 255.255.224.0 and contains thirty-two /24-sized blocks.
/18 subnet: 16,384 total, 16,382 usable IPs
A /18 uses mask 255.255.192.0 and contains sixty-four /24-sized blocks.
/17 subnet: 32,768 total, 32,766 usable IPs
A /17 uses mask 255.255.128.0 and represents half of a /16 network.
/16 subnet: 65,536 total, 65,534 usable IPs
A /16 uses mask 255.255.0.0 and is common as a large private or enterprise network boundary.
/15 subnet: 131,072 total, 131,070 usable IPs
A /15 uses mask 255.254.0.0 and combines two contiguous /16 networks.
/14 subnet: 262,144 total, 262,142 usable IPs
A /14 uses mask 255.252.0.0 and combines four contiguous /16 networks.
/13 subnet: 524,288 total, 524,286 usable IPs
A /13 uses mask 255.248.0.0 and combines eight contiguous /16 networks.
/12 subnet: 1,048,576 total, 1,048,574 usable IPs
A /12 uses mask 255.240.0.0. The private 172.16.0.0–172.31.255.255 range is one familiar /12-sized block.
/11 subnet: 2,097,152 total, 2,097,150 usable IPs
A /11 uses mask 255.224.0.0 and combines thirty-two contiguous /16 networks.
/10 subnet: 4,194,304 total, 4,194,302 usable IPs
A /10 uses mask 255.192.0.0 and represents one quarter of a /8 network.
/9 subnet: 8,388,608 total, 8,388,606 usable IPs
A /9 uses mask 255.128.0.0 and represents half of a /8 network.
/8 subnet: 16,777,216 total, 16,777,214 usable IPs
A /8 uses mask 255.0.0.0. It is a very large block containing 256 contiguous /16 networks.
Which routed IPv4 subnet size should you choose?
- /29 — 6 usable IPs: a few services, mail endpoints, or a small multi-tenant setup.
- /28 — 14 usable IPs: agencies, VM labs, or medium customer and application pools.
- /27 — 30 usable IPs: larger mail, virtualization, proxy, or VPN infrastructure.
Compare ordering and configuration examples in Routed IPv4 subnets for VPS: /29 vs /28 vs /27, browse all routed IPv4 add-ons, or start with an NVMe VPS plan.
IPv4 subnet FAQ
How many IPs are in a /28 subnet?
A /28 has 16 total IPv4 addresses and 14 usable host addresses. Its subnet mask is 255.255.255.240.
What is a /29 subnet mask and how many IPs does it have?
A /29 uses subnet mask 255.255.255.248. It contains 8 total addresses and 6 usable host addresses.
How many usable IPs are in a /30?
A /30 has 4 total addresses and 2 usable host addresses. Its subnet mask is 255.255.255.252.
How many IPs are in a /27 subnet?
A /27 has 32 total addresses and 30 usable host addresses. Its subnet mask is 255.255.255.224.
Why are two addresses unavailable in a normal IPv4 subnet?
The first address identifies the network and the last is the broadcast address. The /31 and /32 prefixes are special exceptions used for point-to-point links and host routes.
Does a routed subnet lose another address to a gateway?
No. When the subnet is routed through a VPS main IP outside the block, no host address inside the block must be assigned as its gateway.
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