IP Subnet Calculator
Free Subnet Calculator – IPv4 & IPv6 (2025)
Instant results • No signup • Mobile friendly • CCNA/CCNP ready
Online IP Subnet Calculator
Trying to divide an IP network without wasting addresses or creating routing headaches? Our completely free subnet calculator does all the heavy lifting in milliseconds — no registration, no ads, no nonsense.
Just enter any IPv4 or IPv6 address with CIDR notation (example: 10.10.0.0/20 or 2001:db8::/48) and instantly see:
- Network address & broadcast address
- Usable host range and total hosts per subnet
- Subnet mask in dot-decimal and binary
- Wildcard mask (perfect for Cisco ACLs and firewall rules)
- Recommended CIDR for a specific number of hosts (reverse subnet lookup)
Why Smart Subnetting Still Matters in 2025
Even with IPv6 adoption growing, most enterprises and cloud environments (AWS VPC, Azure VNet, Google Cloud subnets) still run dual-stack or pure IPv4. Efficient subnetting prevents IP exhaustion, reduces broadcast traffic, and is essential for zero-trust micro-segmentation and SD-WAN deployments.
Key Features You Won’t Find Together Elsewhere
- Cloud-ready presets (AWS /28, Azure-compliant ranges, GCP subnet mode)
- Variable Length Subnet Masking (VLSM) planner – design uneven subnets without overlap
- IPv6 prefix delegation calculator (/48 → /56 → /64 breakdowns)
- One-click copy for Cisco, Juniper, Fortinet, and Palo Alto wildcard masks
- Reverse calculator: “I need 750 usable IPs” → instantly get the tightest CIDR
- Works offline as a Progressive Web App (PWA) on mobile and desktop
Quick Subnetting Cheat Sheet (2025)
| CIDR | Subnet Mask | Usable Hosts | Typical Use Case |
|---|---|---|---|
| /31 | 255.255.255.254 | 2 | Point-to-point links (RFC 3021) |
| /29 | 255.255.255.248 | 6 | Small IoT or management VLANs |
| /24 | 255.255.255.0 | 254 | Standard office LAN |
| /20 | 255.255.240.0 | 4,094 | Medium campus or datacenter segment |
| /16 | 255.255.0.0 | 65,534 | Large private networks |
Who Uses IP Subnet Calculator Daily?
- Network engineers planning VPC peering and transit gateways
- Cybersecurity teams building micro-segmentation policies
- CCNA/CCNP students mastering classless inter-domain routing
- DevOps and cloud architects rightsizing subnets in Terraform or CloudFormation
- Home-lab enthusiasts and Wi-Fi installers separating guest and IoT networks
Whether you’re calculating a simple /24 for a branch office, carving a /48 IPv6 allocation for an ISP customer, or designing complex VLSM hierarchies, this subnetting calculator eliminates human error and saves hours every week IP Subnet Calculator.
Try IP Subnet Calculator now — type any IP address above and watch the magic happen. Bookmark this page; your future self (and your NOC team) will thank you.
Still stuck on a specific scenario? Drop your network requirements in the comments and I’ll reply with the perfect subnet design. Happy subnetting! 🚀
