Subnet CIDR Pro

Subnet CIDR Pro is a focused, offline-first network calculator and VLSM planner built for network engineers, sysadmins, homelab users, and IT students. From quick /30 interface checks to full multi-VLAN allocation plans, get accurate IPv4 subnetting and address tooling directly on your iPhone and iPad—with zero tracking, zero ads, and 100% local calculation. IPv4 & CIDR CALCULATOR • Full Range Support: Calculate any prefix from /0 to /32 • Essential Telemetry: Network, broadcast, subnet mask, wildcard mask, and usable host ranges • Host Capacity: Instant breakdown of total addresses vs. usable host capacity • Modern Link Handling: Full support for /31 point-to-point links (RFC 3021) and /32 host routes • Binary Inspection: Visualize network vs. host bits in clear binary layout • Mask Conversion: Seamless conversion between CIDR prefixes, subnet masks, and wildcard masks • One-Tap Copy: Copy individual values or complete formatted network summaries VLSM NETWORK PLANNING • Requirement-Driven Allocation: Subnet a parent IPv4 block based on exact host requirements • VLAN & Naming: Assign custom network labels and VLAN IDs per subnet • Growth Headroom: Configurable growth reserve percentage per allocation • Gateway Reservation: Optional automatic reservation for default gateway addresses • Space Optimization: View allocated CIDRs alongside remaining unallocated blocks • Overflow Warnings: Instant alerts when requirements exceed parent network capacity ADDRESS TOOLS & IP MATH • Subnet Compare: Test two subnets for containment, overlap, equality, or isolation • IP Membership: Verify instantly whether an IPv4 address belongs to a target network • Range to CIDR: Convert arbitrary start/end IP ranges into minimal exact CIDR blocks • Subnet Splitting: Break down any network into equal-sized child subnets • Supernetting: Summarize adjacent or overlapping subnets into clean aggregation blocks PROJECT WORKSPACE & EXPORT • Project History: Save named planning projects, reopen, rename, or duplicate anytime • Auto-Save: Automatically preserves your current planning draft • Data Export: Export complete subnet plans and available address blocks as CSV • Clipboard Sharing: One-tap copy for formatted plain-text documentation CIDR QUICK REFERENCE TABLE • Interactive reference matrix for all prefixes (/0 to /32) • Searchable by prefix, dotted-decimal mask, wildcard mask, or usable host count • Fast reference copying for switch and firewall configuration DESIGNED FOR iOS & iPadOS • High-contrast dark interface tailored for server rooms and night operations • Adaptive iPad workspace: side-by-side inputs, live results, and wide allocation tables • Localized in 13 languages: English, Simplified & Traditional Chinese, German, French, Japanese, Korean, Italian, Spanish, Brazilian Portuguese, Arabic, Dutch, and Turkish 100% OFFLINE & PRIVATE • Calculations run purely on your device • No account required, no telemetry SDKs, no ads, and no in-app purchases Terms of Use: https://subnet.opshome.run/terms/ Privacy Policy: https://subnet.opshome.run/privacy/ Support: https://subnet.opshome.run/support/