SubnetCalculate

Wildcard Mask Calculator

Enter a subnet mask or wildcard mask to instantly convert between the two formats for Cisco ACL and OSPF configuration. Get the inverse mask, matching IP range, and access list notation — essential for writing Cisco IOS access control lists, OSPF network statements, and router filter rules. Use the ip binary converter to confirm subnet boundary calculations by checking the binary representation of an IP and mask.

Subnet Mask to Wildcard

Wildcard Mask
0.0.0.255

Wildcard to Subnet Mask

Subnet Mask
255.255.255.0
CIDR Notation
/24
Total Addresses
256
Usable Hosts
254

Binary Representation

Subnet Mask:11111111.11111111.11111111.00000000
Wildcard Mask:00000000.00000000.00000000.11111111

Cisco Command Examples

! ACL Example:
access-list 10 permit 192.168.1.0 0.0.0.255
! OSPF Example:
network 192.168.1.0 0.0.0.255 area 0

Common Wildcard Masks

CIDR Subnet Mask Wildcard Mask Hosts
/8 255.0.0.0 0.255.255.255 16,777,214
/16 255.255.0.0 0.0.255.255 65,534
/24 255.255.255.0 0.0.0.255 254
/25 255.255.255.128 0.0.0.127 126
/26 255.255.255.192 0.0.0.63 62
/27 255.255.255.224 0.0.0.31 30
/28 255.255.255.240 0.0.0.15 14
/29 255.255.255.248 0.0.0.7 6
/30 255.255.255.252 0.0.0.3 2
/32 255.255.255.255 0.0.0.0 1

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