How many usable hosts does a /27 subnet have?

A /27 subnet has 30 usable host addresses out of 32 total IPs. Two addresses are reserved: the network address and the broadcast address. In AWS, 27 IPs are usable (5 reserved by AWS). In Azure, 27 IPs are usable (5 reserved by Azure).

What is the subnet mask for a /27 network?

The subnet mask for a /27 network is 255.255.255.224. In binary, 27 bits are set to 1 followed by 5 bits of 0: 11111111.11111111.11111111.11100000.

How many /27 subnets fit inside a /24 network?

A /24 network can be divided into 8 subnets of /27 size. The difference in prefix length is 27 - 24 = 3 bits, and 2^3 = 8. For example, 10.0.0.0/24 contains 10.0.0.0/27, 10.0.0.32/27, 10.0.0.64/27 through 10.0.0.224/27.

What is a /27 Subnet?

Last reviewed: May 2026

A /27 subnet contains 32 total IP addresses and 30 usable host addresses. The "/27" prefix means 27 bits are used for the network portion, leaving 5 bits (2⁵ = 32) for host addressing. The /27 is significant in Azure networking as the minimum required size for GatewaySubnet and RouteServerSubnet.

Calculate any /27 subnet instantly →

Quick Facts: 10.0.0.0/27 Subnet mask: 255.255.255.224 · Wildcard: 0.0.0.31 · Network: x.x.x.0 (on 32-boundary) · Broadcast: x.x.x.31 · Total IPs: 32 · Usable hosts: 30

Full Breakdown

Property	Value
Prefix length	/27
Subnet mask	255.255.255.224
Wildcard mask	0.0.0.31
Total addresses	32
Usable host addresses	30
Network address	x.x.x.0 (must align to multiples of 32: .0, .32, .64, …)
Broadcast address	x.x.x.31 (last address in the block)
Binary mask	11111111.11111111.11111111.11100000
AWS usable hosts	27 (AWS reserves 5 IPs per subnet)
Azure usable hosts	27 (Azure reserves 5 IPs per subnet)

Azure GatewaySubnet Minimum Size

/27 is the minimum size required for Azure GatewaySubnet and RouteServerSubnet. Using a /28 for GatewaySubnet will cause deployment failures when provisioning VPN Gateway or ExpressRoute Gateway. Microsoft recommends /27 as the minimum and /26 or larger for production deployments with ExpressRoute coexistence. Always size your GatewaySubnet at /27 or larger.

Common Use Cases for /27 Subnets

Azure GatewaySubnet — the minimum required prefix for Azure VPN Gateway and ExpressRoute Gateway deployment
Azure RouteServerSubnet — required subnet for Azure Route Server; minimum /27
Infrastructure services — dedicated subnets for NTP servers, DNS resolvers, SNMP collectors, and monitoring agents
Mid-size department VLANs — small teams or office segments needing up to 30 devices
VLSM network design — common building block when subdividing a /24 into 8 equal segments
Printer and device pools — dedicated subnets for shared network devices

Comparison: /27 vs Nearby Prefix Lengths

CIDR	Subnet Mask	Total IPs	Usable Hosts	Azure Usable	Typical Use
/26	255.255.255.192	64	62	59	Azure Firewall, Bastion, App Gateway
/27	255.255.255.224	32	30	27	Azure GatewaySubnet minimum; infrastructure
/28	255.255.255.240	16	14	11	AWS minimum; too small for Azure GatewaySubnet

How Many /27 Subnets Fit in a /24?

A /24 block contains 2^(27−24) = 8 subnets of /27 size. For example, 10.0.0.0/24 can be subdivided into 10.0.0.0/27, 10.0.0.32/27, 10.0.0.64/27, 10.0.0.96/27, 10.0.0.128/27, 10.0.0.160/27, 10.0.0.192/27, and 10.0.0.224/27. Each block starts on a multiple of 32.

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