IPv4 Range Converter

Main Features

• Enter a start and end IPv4 address to calculate the smallest CIDR block that covers the whole range.
• Expand an IPv4 range into a full address list for copying, allowlist cleanup, or inventory verification.
• Split an IPv4 range into the minimal set of CIDR blocks for firewall, routing, or ACL configuration.
• Swap reversed start and end values directly in the tool when the range order is invalid.
• All processing stays in the browser and does not upload your data.

How to Use

1. Enter the start IPv4 address and end IPv4 address at the top of the tool.
2. Open Range to CIDR to view the smallest covering network, aligned boundaries, and address count.
3. Open Range Expansion to view the full IPv4 list within the selected range.
4. Open Split to CIDR to generate the minimal CIDR list that stays inside the original range.
5. Use the copy buttons to copy the CIDR block, aligned boundaries, expanded list, or CIDR list.

Use Cases

• Convert raw start-end address ranges into CIDR blocks for subnet planning and network documentation.
• Review ACL, firewall, or allowlist ranges and verify how the aligned network boundaries change.
• Keep the exact original range by splitting it into multiple CIDR blocks without widening access.
• Expand IPv4 ranges during inventory checks, log review, and troubleshooting tasks.
• Demonstrate how IPv4 range alignment works during training or operations support.

Notes

• Full expansion is limited to 65536 addresses per run. Larger ranges show a head-tail preview to keep the page responsive.
• The CIDR result is the smallest covering network, so it can extend beyond the original input range.
• The input fields accept dotted IPv4 notation only, such as 192.168.1.1.