Subnet Calculator

Calculate network/broadcast address, host range, and subnet mask from IP and CIDR notation.

e.g. 192.168.1.0/24

e.g. 192.168.1.0/24

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Tool Features

CIDR reference: /8 to /32

Usable hosts are total addresses minus the network and broadcast addresses. /31 (point-to-point links, RFC 3021) and /32 (a single host) are the exceptions: every address is usable.

PrefixSubnet maskAddressesUsable hosts
/8255.0.0.016,777,21616,777,214
/9255.128.0.08,388,6088,388,606
/10255.192.0.04,194,3044,194,302
/11255.224.0.02,097,1522,097,150
/12255.240.0.01,048,5761,048,574
/13255.248.0.0524,288524,286
/14255.252.0.0262,144262,142
/15255.254.0.0131,072131,070
/16255.255.0.065,53665,534
/17255.255.128.032,76832,766
/18255.255.192.016,38416,382
/19255.255.224.08,1928,190
/20255.255.240.04,0964,094
/21255.255.248.02,0482,046
/22255.255.252.01,0241,022
/23255.255.254.0512510
/24255.255.255.0256254
/25255.255.255.128128126
/26255.255.255.1926462
/27255.255.255.2243230
/28255.255.255.2401614
/29255.255.255.24886
/30255.255.255.25242
/31255.255.255.25422
/32255.255.255.25511

Usable addresses in cloud subnets (AWS, Azure, Google Cloud)

Cloud providers reserve more addresses than a traditional network does. AWS and Azure reserve five in every subnet (the network address, the next three for the router, DNS and future use, and the last address). Google Cloud reserves four (network, gateway, second-to-last and broadcast). AWS subnets range from /16 to /28; Azure and Google Cloud accept subnets as small as /29.

PrefixAddressesTraditionalAWSAzureGoogle Cloud
/1665,53665,53465,53165,53165,532
/204,0964,0944,0914,0914,092
/221,0241,0221,0191,0191,020
/24256254251251252
/25128126123123124
/266462595960
/273230272728
/281614111112
/2986not allowed34

Subnet Calculator — CIDR & IP Range

Calculate the network address, broadcast address, host range and usable hosts from any IP/CIDR notation. The reference table lists IPv4 subnet sizes from /8 to /32 with mask and host count, plus the usable addresses in AWS, Azure and Google Cloud subnets. Useful for network planning, firewall rules and IP address management.

How It Works

Enter an IP address with a CIDR prefix length (e.g. 192.168.1.0/24). The calculator uses bitwise operations to derive the network address, broadcast address, first/last usable host and wildcard mask. All computation runs in your browser; the CIDR you enter is never sent to our API.

FAQ

What does /24 mean in CIDR notation?

The number after the slash indicates how many bits are used for the network portion. /24 means the first 24 bits are the network (255.255.255.0 mask), leaving 8 bits for hosts — that's 254 usable addresses (256 minus network and broadcast).

How many hosts can a /16 subnet hold?

A /16 subnet has 16 host bits, giving 65,534 usable addresses (2^16 − 2). The subtraction accounts for the network address and broadcast address which cannot be assigned to hosts.

What is the difference between subnet mask and wildcard mask?

A subnet mask marks network bits with 1s and host bits with 0s (e.g. 255.255.255.0). A wildcard mask is the bitwise inverse — host bits are 1s and network bits are 0s (e.g. 0.0.0.255). Wildcard masks are used in ACLs and routing protocols like OSPF.