Subnet Calculator - Calculate Network, Broadcast, and IP Range
Free subnet calculator to compute IPv4 network address, broadcast, wildcard mask, usable range, and host capacity with precise CIDR logic.
Subnet Calculator
Results
Calculations follow standard IPv4 subnetting rules. /31 and /32 are treated as special cases: point-to-point and single-host assignments.
What is a Subnet Calculator?
A subnet calculator is a precise IP planning tool that converts IPv4 address and mask inputs into clear network information: network address, broadcast address, wildcard mask, usable host range, and total addresses for any CIDR block.
This calculator is ideal for:
- Network engineers — Designing LANs, VLANs, VPNs, and WAN segments with clean IP plans.
- DevOps and cloud teams — Planning VPCs, subnets, and routing domains across environments.
- Students & learners — Practicing CIDR, subnetting, and IPv4 fundamentals.
To ensure your subnets map to sufficient throughput for real workloads, check out our Bandwidth Calculator to size internet and WAN links alongside your IP design.
For validating how long large updates or backups across your subnets will take, use our Download Time Calculator to estimate transfer durations over your planned links.
To align addressing plans with server and rack layouts, explore our Server Power Calculator to size power and cooling for the infrastructure behind each subnet.
For designing visually optimized monitoring or console displays connected to your network, try our Screen Resolution Calculator to match resolution and density to NOC dashboards.
To estimate cloud data transfer expenses between segmented environments, use our Data Transfer Cost Calculator to understand the cost impact of your subnet and routing design.
How the Subnet Calculator Works
The logic uses strict IPv4 binary arithmetic to convert CIDR prefixes and subnet masks into network properties.
Where:
- prefix = CIDR length (0–32).
- Mask = 32-bit subnet mask derived from prefix.
- Network/Broadcast = bitwise operations on IP.
- Usable hosts = excludes network and broadcast when applicable.
Key Subnetting Concepts Explained
Network & Broadcast
The network address identifies the subnet; the broadcast address is reserved for reaching all hosts in that subnet.
CIDR & Mask
CIDR /prefix defines how many bits are fixed for the network. The subnet mask is the dotted-decimal representation of that prefix.
Usable Host Range
For most subnets, usable hosts exclude the first (network) and last (broadcast) addresses.
Special Cases
/31 and /32 behave differently: /31 for point-to-point links (2 usable), /32 for a single host or loopback.
How to Use This Subnet Calculator
Enter IPv4 Address
Type any IP in dotted-decimal form, such as 192.168.10.25.
Set CIDR Prefix
Choose /8–/30 for normal subnets, /31 or /32 for special cases.
Optionally Edit Mask
Enter a subnet mask to auto-derive the CIDR prefix.
Click Calculate
View network, broadcast, usable range, and host counts instantly.
Review Address Type
Check if the subnet is private, public, loopback, or reserved.
Use in Network Design
Apply the results to VLANs, firewalls, routing, or cloud VPCs.
Benefits of Using This Subnet Calculator
- • Accurate results: Uses exact CIDR and binary math, eliminating manual mistakes.
- • Ultra-fast planning: Instantly see ranges, hosts, and mask values while designing networks.
- • Clear host capacity: Quickly choose /24, /25, /26, or other sizes based on required hosts.
- • Training-friendly: Ideal for learning subnetting with transparent outputs.
Factors That Affect Your Subnet Design
1. Required Host Count
Always choose a prefix with enough usable IPs for hosts, gateways, VIPs, and future growth.
2. Segmentation & Security
Smaller subnets help isolate services, apply ACLs, and limit broadcast domains.
3. Routing & Summarization
Aggregating contiguous CIDR blocks keeps routing tables smaller and cleaner.
4. Private vs Public Space
Use RFC1918 ranges internally and avoid overlaps across sites and VPNs.
Frequently Asked Questions (FAQ)
Q: What does this subnet calculator do?
A: It computes network address, broadcast, wildcard mask, total addresses, and usable host range for any IPv4 address and CIDR or mask you enter.
Q: How do I choose the right subnet size?
A: Estimate required hosts, then select a prefix where usable hosts meet or exceed that count while avoiding excessive waste.
Q: Why are network and broadcast addresses reserved?
A: The first address identifies the subnet; the last is used for broadcast traffic, so neither should be assigned to hosts in classic IPv4 networks.
Q: How are /31 and /32 handled?
A: /31 is treated as a 2-address subnet commonly used for point-to-point links. /32 represents a single IP, often for loopbacks or host routes.
Q: Does this work for private and public IPs?
A: Yes. The same CIDR math applies; the calculator also labels private, loopback, link-local, and reserved ranges.
Q: Can I rely on this for production network planning?
A: Yes. The calculations follow standard IPv4 subnetting rules. Always validate final designs against organizational policies and documentation.