Subnet calculator

Subnet calculator: network, mask, broadcast and hosts

Paste an address like 192.168.10.37/26 or 10.0.0.1 255.255.255.0. The calculator shows the network it belongs to, the usable host range and how to split the network further.

IP address converter

Enter an IPv4 address, IPv6 address or number to get it in decimal, hex and binary, and for IPv6 in full and compressed form.

IP range to CIDR and address list

Enter a range like 10.0.0.5 - 10.0.0.77 or a subnet like 192.168.1.0/28. You get the CIDR blocks that cover the range and every address as a list.

IPv4 subnet mask table

Prefix	Mask	Wildcard	Addresses	Hosts
/1	128.0.0.0	127.255.255.255	2 147 483 648	2 147 483 646
/2	192.0.0.0	63.255.255.255	1 073 741 824	1 073 741 822
/3	224.0.0.0	31.255.255.255	536 870 912	536 870 910
/4	240.0.0.0	15.255.255.255	268 435 456	268 435 454
/5	248.0.0.0	7.255.255.255	134 217 728	134 217 726
/6	252.0.0.0	3.255.255.255	67 108 864	67 108 862
/7	254.0.0.0	1.255.255.255	33 554 432	33 554 430
/8	255.0.0.0	0.255.255.255	16 777 216	16 777 214
/9	255.128.0.0	0.127.255.255	8 388 608	8 388 606
/10	255.192.0.0	0.63.255.255	4 194 304	4 194 302
/11	255.224.0.0	0.31.255.255	2 097 152	2 097 150
/12	255.240.0.0	0.15.255.255	1 048 576	1 048 574
/13	255.248.0.0	0.7.255.255	524 288	524 286
/14	255.252.0.0	0.3.255.255	262 144	262 142
/15	255.254.0.0	0.1.255.255	131 072	131 070
/16	255.255.0.0	0.0.255.255	65 536	65 534
/17	255.255.128.0	0.0.127.255	32 768	32 766
/18	255.255.192.0	0.0.63.255	16 384	16 382
/19	255.255.224.0	0.0.31.255	8 192	8 190
/20	255.255.240.0	0.0.15.255	4 096	4 094
/21	255.255.248.0	0.0.7.255	2 048	2 046
/22	255.255.252.0	0.0.3.255	1 024	1 022
/23	255.255.254.0	0.0.1.255	512	510
/24	255.255.255.0	0.0.0.255	256	254
/25	255.255.255.128	0.0.0.127	128	126
/26	255.255.255.192	0.0.0.63	64	62
/27	255.255.255.224	0.0.0.31	32	30
/28	255.255.255.240	0.0.0.15	16	14
/29	255.255.255.248	0.0.0.7	8	6
/30	255.255.255.252	0.0.0.3	4	2
/31	255.255.255.254	0.0.0.1	2	2
/32	255.255.255.255	0.0.0.0	1	1

An address block split into smaller CIDR subnets

How the calculator counts

The prefix length says how many leading bits of the address belong to the network. A /26 leaves 6 bits for hosts, which gives 64 addresses: the first is the network address and the last is the broadcast, so 62 are usable.

Networks /31 and /32 are exceptions: a /31 link uses both addresses, and a /32 is a single host. The wildcard mask is the inverted mask that routers and firewalls use in access lists.

When you need it

Allow a whole office network in the IP authorisation of your proxies
Check that two ranges from a provider do not overlap
Plan subnets for servers, VPN and guest Wi-Fi
Turn a mask like 255.255.255.224 into a prefix and back

Questions and answers

01Why are there two fewer hosts than addresses?

In a regular IPv4 network the first address names the network and the last one is the broadcast. Only the addresses between them go to devices.

02How do I turn a mask into a prefix?

Count the one bits of the mask. 255.255.255.0 has 24 of them, so it is /24. The table below lists every mask from /1 to /32.

03How big is an IPv6 /64?

It holds 2^64 addresses. Providers give one /64 per network and a /48 or /56 per customer, so IPv6 planning counts networks, not hosts.

04How do I convert an IP address to a number?

Multiply the first octet by 16,777,216, the second by 65,536, the third by 256, keep the fourth as is and add them up. For 192.168.1.1 you get 3,232,235,777. The converter on this page does it for you and works both ways.

05How do I convert an IP range to CIDR?

Split the range into blocks sized as powers of two, each starting at an address divisible by its size. For 10.0.0.5 to 10.0.0.77 you get eight blocks, from 10.0.0.5/32 to 10.0.0.76/31. The IP range to CIDR block on this page does it for you.