IP Subnet Calculator · Practical guide
How Many IP Addresses Are in a /24?
A /24 gives you 256 addresses total, but only 254 are usable — here's where the other two go.
At a glance
The Answer: 256 Total, 254 Usable
A /24 prefix leaves 8 bits for hosts (32 − 24 = 8), and 2^8 = 256 addresses. Two are reserved: the first is the network address and the last is the broadcast address, so 254 addresses can be assigned to devices. For the classic 192.168.1.0/24 home network, usable addresses run from 192.168.1.1 to 192.168.1.254.
Interactive tool
IP Subnet Calculator
Enter your own values, then compare the result with the examples below.
Subnet Details
The Math Behind It
The number after the slash counts how many of the 32 address bits identify the network. Everything left over identifies hosts. Total addresses = 2^(32 − prefix); usable hosts = that minus 2. Enter any IP and prefix in the calculator above to see the exact network, broadcast, and host range.
Common Prefix Sizes Compared
| Prefix | Total Addresses | Usable Hosts | Subnet Mask |
|---|---|---|---|
| /16 | 65,536 | 65,534 | 255.255.0.0 |
| /20 | 4,096 | 4,094 | 255.255.240.0 |
| /24 | 256 | 254 | 255.255.255.0 |
| /25 | 128 | 126 | 255.255.255.128 |
| /26 | 64 | 62 | 255.255.255.192 |
| /28 | 16 | 14 | 255.255.255.240 |
| /30 | 4 | 2 | 255.255.255.252 |
The Two Exceptions: /31 and /32
A /31 is used for point-to-point links between two routers. It has exactly 2 addresses and, per RFC 3021, both are usable — there's no broadcast on a two-device link. A /32 identifies a single host, with 1 address. The calculator above handles both cases correctly instead of subtracting two.
Frequently Asked Questions
Why can't hosts use the first and last addresses in a /24?
The first address (like 192.168.1.0) names the network itself, and the last (192.168.1.255) is the broadcast address that reaches every device on the subnet. Assigning either to a device causes routing and delivery problems.
Is a /24 the same as 255.255.255.0?
Yes, exactly. The /24 means 24 leading 1-bits in the mask, which written in dotted decimal is 255.255.255.0. They're two notations for the same thing.
How many /24 subnets fit in a /16?
256 of them. A /16 has 65,536 addresses and a /24 has 256, so 65,536 ÷ 256 = 256 subnets — for example, 10.0.0.0/24 through 10.0.255.0/24.
Is 192.168.1.0/24 a private network?
Yes. Anything in 192.168.0.0/16, 10.0.0.0/8, or 172.16.0.0/12 is private address space reserved by RFC 1918 and never routed on the public internet.