/13 Subnet Mask ReferenceIPv4
Eight consecutive /16s summarized in one line: mask <code>255.248.0.0</code>, 524,288 addresses. A /13 is sized for a national ISP region and rare enough that spotting one in a design review starts a conversation.
/13 facts at a glance
- Subnet mask
- 255.248.0.0
- Wildcard mask
- 0.7.255.255
- Binary mask
- 11111111.11111000.00000000.00000000
- Total addresses
- 524,288
- Usable hosts
- 524,286 (excludes network & broadcast)
- Block size
- 524,288 addresses (219)
- Typical role
- Large enterprise and carrier aggregation
Example /13 networks
Three consecutive /13 blocks, starting at the /13 boundary that contains 198.51.100.0:
| Network | Usable range | Usable hosts |
|---|---|---|
| 198.48.0.0/13 | 198.48.0.1 – 198.55.255.254 | 524,286 |
| 198.56.0.0/13 | 198.56.0.1 – 198.63.255.254 | 524,286 |
| 198.64.0.0/13 | 198.64.0.1 – 198.71.255.254 | 524,286 |
How to calculate a /13 mask
A /13 mask sets the first 13 bits of a 32-bit number to 1 and leaves the remaining 19 bits as 0. In binary that reads 11111111.11111000.00000000.00000000, which converts to dotted decimal 255.248.0.0. Each block covers a contiguous run of 219 = 524,288 addresses, and every block starts at a multiple of that size. The wildcard simply flips every bit, giving 0.7.255.255.
Where /13 is used
- Regional aggregation planning for large network operators.
- Structured multi-campus addressing where each child site takes a /16 or smaller.
- Advanced coursework on masks that stop five bits into the second octet.
Worked example: <code>88.0.0.0/13</code> spans 88.0.0.0 through 95.255.255.255, eight complete /8s swallowed by a single summary.
Frequently asked questions
What is the mask for a /13?
<code>255.248.0.0</code>, wildcard <code>0.7.255.255</code>.
How many addresses are in a /13?
524,288 total and 524,286 usable by convention.
How many /16s are in a /13?
Eight. Equivalently, a /13 contains 2,048 /24-sized networks.
Open this block in a calculator
Open the /13 block in the subnet calculator