# /15 Subnet Mask (255.254.0.0) – Hosts, Range & FAQ

> The /15 subnet mask is 255.254.0.0. A /15 block holds 131,072 addresses with 131,070 usable hosts — ranges, wildcard, binary math and FAQs.

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# /15 Subnet Mask ReferenceIPv4

Pair two adjacent /16s and the natural summary is a /15: mask 255.254.0.0, 131,072 addresses. It is the tidy answer when two campuses or two data halls share one routing domain.

The /15 subnet mask is 255.254.0.0, equivalent to 0.1.255.255 as a wildcard. A /15 block contains 131,072 IP addresses (131,070 usable hosts).

## /15 facts at a glance

- **Subnet mask:** 255.254.0.0
- **Wildcard mask:** 0.1.255.255
- **Binary mask:** 11111111.11111110.00000000.00000000
- **Total addresses:** 131,072
- **Usable hosts:** 131,070 (excludes network & broadcast)
- **Block size:** 131,072 addresses (217)
- **Typical role:** Large enterprise and carrier aggregation

## Example /15 networks

Three consecutive /15 blocks, starting at the /15 boundary that contains 198.51.100.0:

| Network | Usable range | Usable hosts |
| --- | --- | --- |
| 198.50.0.0/15 | 198.50.0.1 – 198.51.255.254 | 131,070 |
| 198.52.0.0/15 | 198.52.0.1 – 198.53.255.254 | 131,070 |
| 198.54.0.0/15 | 198.54.0.1 – 198.55.255.254 | 131,070 |

## How to calculate a /15 mask

A /15 mask sets the first 15 bits of a 32-bit number to 1 and leaves the remaining 17 bits as 0. In binary that reads `11111111.11111110.00000000.00000000`, which converts to dotted decimal `255.254.0.0`. Each block covers a contiguous run of 217 = 131,072 addresses, and every block starts at a multiple of that size. The wildcard simply flips every bit, giving `0.1.255.255`.

## Where /15 is used

- Merging two /16 sites under a single advertisement.
- Paired data-center blocks planned symmetrically from day one.
- Supernetting practice on the odd/even second-octet boundary.

Famous resident: 198.18.0.0/15 is reserved for benchmarking network equipment (RFC 2544), spanning 198.18.0.0 through 198.19.255.255.

The second octet must be even: 130.10.0.0/15 is legal and covers 130.10.0.0 through 130.11.255.255, while 130.11.0.0/15 is misaligned.

## Frequently asked questions

**What mask does a /15 use?**

255.254.0.0, wildcard 0.1.255.255.

**How many addresses are in a /15?**

131,072 total; 131,070 usable after removing the network and broadcast placeholders.

**How many /16s are in a /15?**

Exactly two: an even-numbered /16 plus the odd one immediately following it.

## Open this block in a calculator

[Open the /15 block in the subnet calculator](https://itinsighthub.com/subnet-calculator/?q=198.50.0.0%2F15)

[Get the /15 wildcard mask →](https://itinsighthub.com/wildcard-mask-calculator/?q=%2F15)

### Related prefixes

[/14](https://itinsighthub.com/subnet/14/)[/16](https://itinsighthub.com/subnet/16/)[/24](https://itinsighthub.com/subnet/24/)[/26](https://itinsighthub.com/subnet/26/)[/28](https://itinsighthub.com/subnet/28/)[/30](https://itinsighthub.com/subnet/30/)

← /14 subnet mask
/16 subnet mask →

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