Subnet calculator
Network, broadcast, host range and mask for a block.
Try
- Network
- 172.16.40.0
- Broadcast
- 172.16.47.255
- First host
- 172.16.40.1
- Last host
- 172.16.47.254
- Usable hosts
- 2,046
- Total
- 2,048
- Mask
- 255.255.248.0
- Wildcard
- 0.0.7.255
- Type
- Private (RFC 1918)
- Class
- Bhistorical, before CIDR
- Hex
- 0xAC102800
- Integer
- 2886739968
- Reverse DNS
- 0.40.16.172.in-addr.arpa
- IPv4-mapped
- ::ffff:172.16.40.0
Bits
Binary
- Network
- 10101100.00010000.00101000.00000000
- Broadcast
- 10101100.00010000.00101111.11111111
- Mask
- 11111111.11111111.11111000.00000000
- Wildcard
- 00000000.00000000.00000111.11111111
8 subnets · 254 usable hosts each
- 1172.16.40.0/24254
- 2172.16.41.0/24254
- 3172.16.42.0/24254
- 4172.16.43.0/24254
- 5172.16.44.0/24254
- 6172.16.45.0/24254
- 7172.16.46.0/24254
- 8172.16.47.0/24254
172.16.40.0/21, 2,046 usable hosts
About this tool
- Runs in
- your browser
- Your input sent to our servers
- Nothing
- Kept on this device
- nothing
More in the privacy policy.
How to use it
- 01Type or paste an address with a prefix, such as 10.0.0.0/8 or 2001:db8::/32, or pick one under Try.
- 02Read the network, usable range and mask (and broadcast for IPv4), and copy any value. Below them are the address you typed in other forms: its reverse DNS name and, for IPv4, its class, hex and integer forms and its IPv4-mapped IPv6 address.
- 03Choose Split into to cut the block into equal subnets, then copy them all or download CSV.
Related tools
Questions
Why are there 2 fewer usable hosts than addresses?
The first address identifies the network and the last is the broadcast address, so a /24 has 256 addresses and 254 usable hosts. A /31 point-to-point link uses both of its addresses (RFC 3021), and a /32 is a single host.
What is the wildcard mask?
The subnet mask with every bit flipped: 0.0.7.255 for a /21. Cisco access lists and OSPF use it.
What are address classes?
Before CIDR replaced them in 1993, the first bits of an IPv4 address fixed its network size: class A (first byte 0–127) was a /8, class B (128–191) a /16 and class C (192–223) a /24; class D (224–239) is multicast and class E (240–255) reserved. Networks are no longer sized by class, but the terms still appear in exams and older documentation.
Is my input sent anywhere?
No. The calculator runs in this tab. Your input isn't sent to our servers, and it isn't kept after you leave the page.