# /18 Subnet Mask (255.255.192.0) – Hosts, Range & FAQ

> The /18 subnet mask is 255.255.192.0. A /18 block holds 16,384 addresses with 16,382 usable hosts — ranges, wildcard, binary math and FAQs.

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# /18 Subnet Mask ReferenceIPv4

A quarter of a /16, sixty-four /24s deep: 255.255.192.0 marks the /18, comfortable for 16,382 hosts. Manufacturing floors and hospital wings fit inside one with space left over.

The /18 subnet mask is 255.255.192.0, equivalent to 0.0.63.255 as a wildcard. A /18 block contains 16,384 IP addresses (16,382 usable hosts).

## /18 facts at a glance

- **Subnet mask:** 255.255.192.0
- **Wildcard mask:** 0.0.63.255
- **Binary mask:** 11111111.11111111.11000000.00000000
- **Total addresses:** 16,384
- **Usable hosts:** 16,382 (excludes network & broadcast)
- **Block size:** 16,384 addresses (214)
- **Typical role:** Mid-size networks and ISP allocations

## Example /18 networks

Three consecutive /18 blocks, starting at the /18 boundary that contains 198.51.100.0:

| Network | Usable range | Usable hosts |
| --- | --- | --- |
| 198.51.64.0/18 | 198.51.64.1 – 198.51.127.254 | 16,382 |
| 198.51.128.0/18 | 198.51.128.1 – 198.51.191.254 | 16,382 |
| 198.51.192.0/18 | 198.51.192.1 – 198.51.255.254 | 16,382 |

## How to calculate a /18 mask

A /18 mask sets the first 18 bits of a 32-bit number to 1 and leaves the remaining 14 bits as 0. In binary that reads `11111111.11111111.11000000.00000000`, which converts to dotted decimal `255.255.192.0`. Each block covers a contiguous run of 214 = 16,384 addresses, and every block starts at a multiple of that size. The wildcard simply flips every bit, giving `0.0.63.255`.

## Where /18 is used

- Single-building production and guest separation without touching the rest of a /16.
- Mid-size site cores that feed smaller /24 VLANs downstream.
- Starting blocks for VLSM plans mixing large and small departments.

Alignment rule: the third octet must sit on a multiple of 64. 10.1.64.0/18 spans 10.1.64.0 through 10.1.127.255.

## Frequently asked questions

**What is the subnet mask for /18?**

255.255.192.0, wildcard 0.0.63.255.

**How many usable hosts does a /18 have?**

16,382 of 16,384 total addresses.

**How many /24s fit in a /18?**

Sixty-four, stepping the third octet through its full range within one /18 block.

## Open this block in a calculator

[Open the /18 block in the subnet calculator](https://itinsighthub.com/subnet-calculator/?q=198.51.64.0%2F18)

[Get the /18 wildcard mask →](https://itinsighthub.com/wildcard-mask-calculator/?q=%2F18)

### Related prefixes

[/17](https://itinsighthub.com/subnet/17/)[/19](https://itinsighthub.com/subnet/19/)[/24](https://itinsighthub.com/subnet/24/)[/26](https://itinsighthub.com/subnet/26/)[/28](https://itinsighthub.com/subnet/28/)[/30](https://itinsighthub.com/subnet/30/)

← /17 subnet mask
/19 subnet mask →

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