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 subnet mask calculator to convert between CIDR notation and dotted-decimal mask format for firewall and ACL configuration.

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

CIDRSubnet MaskWildcard MaskHosts
/8255.0.0.00.255.255.25516,777,214
/16255.255.0.00.0.255.25565,534
/24255.255.255.00.0.0.255254
/25255.255.255.1280.0.0.127126
/26255.255.255.1920.0.0.6362
/27255.255.255.2240.0.0.3130
/28255.255.255.2400.0.0.1514
/29255.255.255.2480.0.0.76
/30255.255.255.2520.0.0.32
/32255.255.255.2550.0.0.01

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