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IP Range CalculatorPRO
Masks, Wildcards & ACLInstant Client-Side Tool

ACL Wildcard to CIDR Converter

Express matching addresses as CIDR blocks.

ACL Wildcard to CIDR Converter: inputs and results

Enter an IP address, CIDR prefix, or range. Then check its first and last address below.

Quick presets:

Calculated Boundaries & ParametersReady

Network Address192.168.1.0
Broadcast Address192.168.1.255
First Usable Host192.168.1.1
Last Usable Host192.168.1.254
Subnet Mask255.255.255.0
Wildcard Mask0.0.0.255
Total Addresses256
Usable Host Range254

Key Capabilities

  • •100% Client-Side: Zero telemetry or server latency.
  • •RFC Compliant: Exact 32-bit and 128-bit integer precision.
  • •Quick Copy: Instant access to CIDR, mask, and range bounds.
  • •Cross-Platform: Works on desktop, tablet, and mobile browsers.
Open Full Interactive Suite

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Subnet Mask to Wildcard Converter

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Wildcard Mask to Subnet Mask Converter

Convert compatible contiguous wildcard masks.

How ACL Wildcard to CIDR Converter Works?

This tool works by splitting the wildcard into a contiguous trailing run, which sets the block size, and any extra 1 bits, which set how many blocks appear.

  1. Enter base and wildcard

    Type 10.0.0.0 0.0.6.255.

  2. Find the trailing run

    The rightmost 8 bits are 1, so each block is a /24.

  3. Find the extra bits

    Octet 3 value 6 = 00000110 adds 2 extra bits, so 2^2 = 4 blocks exist.

  4. List the blocks

    The converter enumerates 10.0.0.0/24, 10.0.2.0/24, 10.0.4.0/24, and 10.0.6.0/24.

ACL Wildcard to CIDR Converter Formula

The formula is Blocks = 2^k, each of prefix 32 − t, where t is the trailing run of 1 bits and k is the count of other 1 bits.

Trailing run

t = count of consecutive 1 bits from the right

Sets the block size.

Block prefix

p = 32 − t

/24 when t = 8.

Extra bits

k = popcount(W) − t

Non-contiguous 1 bits.

Block count

2^k

1 block for a contiguous wildcard.

Worked example: 10.0.0.0 0.0.6.255

Wildcard bits: 00000000.00000000.00000110.11111111
t = 8 → /24     k = 2 → 4 blocks
  10.0.0.0/24
  10.0.2.0/24
  10.0.4.0/24
  10.0.6.0/24

ACL Wildcard to CIDR Converter Conversion Table

The table expands 9 base-and-wildcard pairs into CIDR blocks, showing the block count and the resulting prefixes.

BaseWildcardBlocksCIDR Result
10.1.0.00.0.255.255110.1.0.0/16
10.0.0.00.0.6.255410.0.0.0/24, 10.0.2.0/24, 10.0.4.0/24, 10.0.6.0/24
192.168.0.00.0.1.2551192.168.0.0/23
172.16.0.10.0.0.01172.16.0.1/32
10.0.0.10.0.3.0410.0.0.1/32, 10.0.1.1/32, 10.0.2.1/32, 10.0.3.1/32
192.168.0.00.0.12.2554192.168.0.0/24, 192.168.4.0/24, 192.168.8.0/24, 192.168.12.0/24
10.10.0.00.0.0.127110.10.0.0/25
172.16.0.00.0.16.2552172.16.0.0/24, 172.16.16.0/24
10.0.0.00.0.254.25512810.0.0.0/24, 10.0.2.0/24 … 10.0.254.0/24

What is ACL Wildcard to CIDR Converter?

The ACL Wildcard to CIDR Converter is a tool that expresses the addresses matched by an ACL base and wildcard as a list of CIDR blocks.

A contiguous wildcard becomes 1 CIDR block. A non-contiguous wildcard becomes several blocks. 10.0.0.0 0.0.254.255 matches 128 separate /24 subnets, one for every even third octet.

Firewalls, cloud security groups, and most non-Cisco platforms accept CIDR blocks only. The converter turns any wildcard rule into a format those platforms understand.

What are the uses of ACL Wildcard to CIDR Converter?

There are 4 main uses of the ACL Wildcard to CIDR Converter, including firewall migration, cloud translation, and rule audits.

  • Migrating Cisco ACLs to firewalls

    Next-generation firewalls need CIDR objects. The converter turns each ACL line into those objects.

  • Translating rules to cloud security groups

    Security groups accept CIDR only, so wildcard rules are expanded first.

  • Measuring rule scope

    The block count shows how many subnets a single wildcard line covers.

  • Documenting legacy rules

    CIDR lists are easier to read than non-contiguous wildcards in audit reports.