CIDR and subnet calculator

See exactly which bits are the network and which are the host, for IPv4 and IPv6. Split blocks, check whether an address is inside, and find out if a range is private, reserved or public.

10.20.0.0/22 is 1,024 addresses: 10.20.0.0 to 10.20.3.255. 1,022 usable for hosts (the first is the network address, the last is broadcast).

10000010102000010100000000000000000000

22 network bits 10 host bits

Network: 10.20.0.0
First usable: 10.20.0.1
Last usable: 10.20.3.254
Broadcast: 10.20.3.255
Addresses: 1,024
Usable hosts: 1,022
Netmask: 255.255.252.0
Wildcard (ACL) mask: 0.0.3.255
Historic class: A
Range type: Private network · not routed on the internet

Special-purpose range

Private network 10.0.0.0/8 RFC 1918
The largest of the three private IPv4 ranges: 16.7 million addresses for use inside homes and organisations. Not routed on the public internet.

Split it into subnets

4 subnets.

Subnet	Usable range	Hosts	Broadcast
`10.20.0.0/24`	`10.20.0.1` – `10.20.0.254`	254	`10.20.0.255`
`10.20.1.0/24`	`10.20.1.1` – `10.20.1.254`	254	`10.20.1.255`
`10.20.2.0/24`	`10.20.2.1` – `10.20.2.254`	254	`10.20.2.255`
`10.20.3.0/24`	`10.20.3.1` – `10.20.3.254`	254	`10.20.3.255`

Is this IP in the range?

Range to CIDR blocks

Special-purpose ranges

From the IANA IPv4 and IPv6 Special-Purpose Address Registries, plus multicast and global unicast. "Routable" is the registry's "globally reachable" column.

Block	What it is	Routable	RFC
`0.0.0.0/8`	This network	no	RFC 791
`10.0.0.0/8`	Private network	no	RFC 1918
`100.64.0.0/10`	Shared address space (carrier-grade NAT)	no	RFC 6598
`127.0.0.0/8`	Loopback	no	RFC 1122
`169.254.0.0/16`	Link-local	no	RFC 3927
`172.16.0.0/12`	Private network	no	RFC 1918
`192.0.0.0/24`	IETF protocol assignments	no	RFC 6890
`192.0.2.0/24`	Documentation (TEST-NET-1)	no	RFC 5737
`192.31.196.0/24`	AS112-v4	yes	RFC 7535
`192.52.193.0/24`	AMT	yes	RFC 7450
`192.88.99.0/24`	Deprecated 6to4 relay anycast	n/a	RFC 7526
`192.168.0.0/16`	Private network	no	RFC 1918
`192.175.48.0/24`	Direct delegation AS112 service	yes	RFC 7534
`198.18.0.0/15`	Benchmarking	no	RFC 2544
`198.51.100.0/24`	Documentation (TEST-NET-2)	no	RFC 5737
`203.0.113.0/24`	Documentation (TEST-NET-3)	no	RFC 5737
`224.0.0.0/4`	Multicast	n/a	RFC 5771
`240.0.0.0/4`	Reserved for future use	no	RFC 1112
`255.255.255.255/32`	Limited broadcast	no	RFC 919
`::/128`	Unspecified address	no	RFC 4291
`::1/128`	Loopback	no	RFC 4291
`::ffff:0:0/96`	IPv4-mapped address	no	RFC 4291
`64:ff9b::/96`	IPv4/IPv6 translation (NAT64)	yes	RFC 6052
`64:ff9b:1::/48`	Local-use IPv4/IPv6 translation	no	RFC 8215
`100::/64`	Discard-only	no	RFC 6666
`2001::/23`	IETF protocol assignments	no	RFC 2928
`2001::/32`	Teredo	n/a	RFC 4380
`2001:2::/48`	Benchmarking	no	RFC 5180
`2001:db8::/32`	Documentation	no	RFC 3849
`2002::/16`	6to4	n/a	RFC 3056
`3fff::/20`	Documentation	no	RFC 9637
`fc00::/7`	Unique local address (ULA)	no	RFC 4193
`fe80::/10`	Link-local unicast	no	RFC 4291
`ff00::/8`	Multicast	n/a	RFC 4291
`2000::/3`	Global unicast	yes	RFC 4291