/0 subnet: mask 0.0.0.0, 4,294,967,296 addresses

Everything about a /0 network, with the CIDR calculator pre-filled — change the IP to calculate your own block.

CIDR, IP range, or IP + subnet mask

Enter a CIDR range above to calculate

Is an IP inside a CIDR block?

Yes — 10.0.42.7 is inside 10.0.0.0/16.

Do two CIDR blocks overlap?

Overlap — 10.0.128.0/20 sits inside 10.0.0.0/16 (10.0.128.0 – 10.0.143.255).

CIDR blocks never partly overlap: one is inside the other, or they don't touch at all. Overlapping VPCs can't be peered.

/0 at a glance

Subnet mask: 0.0.0.0
Wildcard mask: 255.255.255.255
Mask in binary: 00000000.00000000.00000000.00000000
Host bits: 32
Total addresses: 4,294,967,296
Usable hosts: 4,294,967,294 (network and broadcast address excluded)
Equivalent /24 networks: 16,777,216

Means "every IPv4 address". You see 0.0.0.0/0 as the default route and in firewall rules that allow or block all traffic — handle with care.

Splitting a /0 into smaller subnets

2 × /1 — 2,147,483,648 addresses each (2,147,483,646 usable)
4 × /2 — 1,073,741,824 addresses each (1,073,741,822 usable)
8 × /3 — 536,870,912 addresses each (536,870,910 usable)
16 × /4 — 268,435,456 addresses each (268,435,454 usable)

Frequently asked

What is the subnet mask for /0?

0.0.0.0. The first 0 bits are network bits and the remaining 32 are host bits; the wildcard (inverse) mask is 255.255.255.255.

How many IP addresses are in a /0?

4,294,967,296 in total. 4,294,967,294 of them can be assigned to hosts, because the first is the network address and the last is the broadcast address.

CIDR to subnet mask cheat sheet

CIDR	Subnet mask	Addresses	Usable hosts
/8	255.0.0.0	16,777,216	16,777,214
/12	255.240.0.0	1,048,576	1,048,574
/16	255.255.0.0	65,536	65,534
/17	255.255.128.0	32,768	32,766
/18	255.255.192.0	16,384	16,382
/19	255.255.224.0	8,192	8,190
/20	255.255.240.0	4,096	4,094
/21	255.255.248.0	2,048	2,046
/22	255.255.252.0	1,024	1,022
/23	255.255.254.0	512	510
/24	255.255.255.0	256	254
/25	255.255.255.128	128	126
/26	255.255.255.192	64	62
/27	255.255.255.224	32	30
/28	255.255.255.240	16	14
/29	255.255.255.248	8	6
/30	255.255.255.252	4	2
/31	255.255.255.254	2	2
/32	255.255.255.255	1	1