SubnetPad

/12 Subnet Calculator

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A /12 block contains 1,048,576 addresses. The entire 172.16.0.0/12 range is reserved by RFC 1918 for private networking — covering 172.16.x.x through 172.31.x.x.

/1
/32

/12 = mask 255.240.0.0 • 1,048,574 usable addresses

Results for 172.16.0.0/12

Private (RFC 1918)Class B
Network addressThe first address — identifies the subnet itself
Broadcast addressThe last address — used to reach every device at once
Subnet maskSame as /12 in CIDR notation
First usable hostThe first IP you can assign to a device
Last usable hostThe last IP you can assign to a device
Usable hosts1,048,576 total addresses in this subnet
More detailsNeighboring subnets, wildcard mask, hex, reverse DNS, and binary breakdown

Neighboring /12 subnets

Wildcard mask
Used in Cisco ACLs and OSPF
CIDR notation
IP in hexadecimal
IP as 32-bit integer
Reverse DNS (PTR)
Host bits / subnet bits

Binary breakdown

IP address10101100.00010000.00000000.00000000
Subnet mask11111111.11110000.00000000.00000000
Network10101100.00010000.00000000.00000000
Broadcast10101100.00011111.11111111.11111111

Quick facts for /12

/12 reference guideBit split, overview, sizing tables, notable networks, and FAQ

Binary bit split

Network bits (12)Host bits (20)
Network bits
12
Host bits
20
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255
Total addresses
1,048,576
Usable hosts
1,048,574
Hosts formula
2^20 − 2
/24 relationship
4,096 × /24 networks

Overview

A /12 block contains 1,048,576 addresses. The entire 172.16.0.0/12 range is reserved by RFC 1918 for private networking — covering 172.16.x.x through 172.31.x.x.

Common use cases

  • RFC 1918 Class B private range (172.16.0.0/12)
  • Docker default network bridge addressing
  • Large enterprise multi-site addressing
  • Cloud VPC address pools

Subnet sizing reference

Divide /12 into…

PrefixSubnetsHosts each
/132524,286
/144262,142
/158131,070
/161665,534

/12 fits inside…

SupernetHosts/12s inside
/112,097,1502
/104,194,3024
/98,388,6068
/816,777,21416

Notable /12 networks

  • 172.16.0.0/12RFC 1918 Class B private range

Frequently asked questions

Common questions about /12 networks, subnet masks, and use cases.

All CIDR prefix sizes

/0/1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/31/32