Subnet Calculator
- CIDR
- 192.168.1.0/24
- Network address
- 192.168.1.0
- Usable range
- 192.168.1.1 to 192.168.1.254
- Broadcast address
- 192.168.1.255
- Total addresses
- 256
- Usable hosts
- 254
- Netmask
- 255.255.255.0
- Wildcard mask
- 0.0.0.255
- Class
- C
- Scope
- Private (RFC 1918)
| AWS | 251 (5 reserved) |
| Azure | 251 (5 reserved) |
| Google Cloud | 252 (4 reserved) |
Split into smaller subnets
Pick a longer prefix to divide 192.168.1.0/24 into equal blocks, useful for planning VPC subnets across availability zones.
IPv4 networks, netmasks and host ranges, with a splitter for planning VPC subnets.
Usable addresses in AWS, Azure and Google Cloud
A textbook /24 has 254 usable hosts. In a cloud VPC it has fewer. AWS and Azure reserve the first four addresses and the last in every subnet, for the network, the router or gateway, DNS and the broadcast address. Google Cloud reserves four: the network, the gateway, the second-to-last and the broadcast. Each also limits subnet size, which is where not allowed comes from below.
| Prefix | Addresses | AWS | Azure | Google Cloud |
|---|---|---|---|---|
| /16 | 65,536 | 65,531 | 65,531 | 65,532 |
| /20 | 4,096 | 4,091 | 4,091 | 4,092 |
| /22 | 1,024 | 1,019 | 1,019 | 1,020 |
| /24 | 256 | 251 | 251 | 252 |
| /25 | 128 | 123 | 123 | 124 |
| /26 | 64 | 59 | 59 | 60 |
| /27 | 32 | 27 | 27 | 28 |
| /28 | 16 | 11 | 11 | 12 |
| /29 | 8 | not allowed | 3 | 4 |
Limits: AWS subnets run from /16 to /28, Azure from /2 to /29, and Google Cloud primary ranges from /4 to /29, though Google advises nothing larger than /8. Checked against each provider's documentation in September 2026.
Subnet calculator FAQs
How do I read CIDR notation like /24?
The number after the slash is how many leading bits of the address are the network part. A /24 fixes the first 24 bits, leaving 8 for hosts: 256 addresses, 254 of them usable. Smaller numbers mean bigger networks; a /16 holds 65,536 addresses.
Why are two addresses missing from every subnet?
The lowest address names the network itself and the highest is the broadcast address, so a /24 offers 254 usable hosts rather than 256. The exceptions are /31, defined by RFC 3021 for point-to-point links with both addresses usable, and /32, a single host route.
Which address ranges are private?
Three ranges are reserved for private use by RFC 1918: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. They are not routable on the public internet, which is why they appear in almost every office network and cloud VPC. The calculator labels these plus loopback, link-local, carrier-grade NAT and multicast ranges.
How do I plan subnets for a cloud VPC?
Start with the VPC block, say a /16, then use the split section to divide it at a longer prefix. A common pattern is one pair of subnets per availability zone, public and private, sized to leave room to grow. Size them on the cloud figure rather than the textbook one: AWS and Azure keep five addresses in every subnet and Google Cloud keeps four, which the calculator shows for whatever block you enter.
How many IP addresses does AWS reserve in a subnet?
Five: the first four and the last. In 10.0.0.0/24 those are 10.0.0.0 for the network, 10.0.0.1 for the VPC router, 10.0.0.2 for Amazon DNS, 10.0.0.3 held for future use, and 10.0.0.255, the broadcast address a VPC does not support. A /24 therefore gives 251 usable addresses, and the smallest subnet AWS allows, a /28, gives 11. Azure also reserves five; Google Cloud reserves four.
What is a wildcard mask?
The bitwise inverse of the netmask, used by router access lists and some firewall rules. Where the netmask for a /24 is 255.255.255.0, the wildcard is 0.0.0.255.
Is anything I type sent to a server?
No. All calculation happens in your browser and the page keeps working offline. Address plans are sensitive infrastructure detail, and they stay on your machine.