IP Address Planning Calculator
Enter your parent network and per-segment host requirements to get real, computed IPv4 subnet allocations — CIDR blocks, masks, and usable ranges. Calculated in your browser, no account required.
Free to use · no account required
IP Address Planning Calculator
Everything below is calculated instantly in your browser as you type — nothing is submitted or stored.
IT KORR
IP Address Planning Calculator
Real IPv4/CIDR math, calculated entirely in your browser.
Addresses Used
1,216
Remaining Capacity
64,320
Utilization
1.9%
| Segment | Hosts | CIDR | Mask | Usable Range | Broadcast | Usable Hosts |
|---|---|---|---|---|---|---|
| Servers | 200 | 10.0.2.0/24 | 255.255.255.0 | 10.0.2.1 – 10.0.2.254 | 10.0.2.255 | 254 |
| Workstations | 500 | 10.0.0.0/23 | 255.255.254.0 | 10.0.0.1 – 10.0.1.254 | 10.0.1.255 | 510 |
| Voice | 100 | 10.0.4.0/25 | 255.255.255.128 | 10.0.4.1 – 10.0.4.126 | 10.0.4.127 | 126 |
| Guest | 250 | 10.0.3.0/24 | 255.255.255.0 | 10.0.3.1 – 10.0.3.254 | 10.0.3.255 | 254 |
| Management | 50 | 10.0.4.128/26 | 255.255.255.192 | 10.0.4.129 – 10.0.4.190 | 10.0.4.191 | 62 |
Allocated using VLSM (largest requirement first) from 10.0.0.0/16 — 65,536 total addresses in the parent network. This is a planning calculation, not a deployed configuration — verify against your actual routing and firewall design before implementation.
How It Works
What this tool does with your input
How this tool works, and what happens to what you enter
- You
You describe the environment
Capacity, power, redundancy and term — the inputs that genuinely change the number.
- The tool
The model runs in your browser
Arithmetic only, executed locally.
- You
You get an itemised estimate
The figure and the assumptions behind it, so you can argue with both.
What The Inputs Mean
What Shapes Your Allocation
Area
What the tool evaluates
Parent Network
The private address space you're allocating from — the calculator validates every segment fits within it before producing a plan.
Segment Host Counts
The number of usable hosts each segment needs determines the smallest valid CIDR block for that segment.
VLSM Allocation Order
Segments are packed largest-requirement-first to minimize wasted address space, then aligned to valid subnet boundaries.
Parent Network
The private address space you're allocating from — the calculator validates every segment fits within it before producing a plan.
Segment Host Counts
The number of usable hosts each segment needs determines the smallest valid CIDR block for that segment.
VLSM Allocation Order
Segments are packed largest-requirement-first to minimize wasted address space, then aligned to valid subnet boundaries.
Understanding Your Results
A Real Computed Address Plan
This tool performs real IPv4 CIDR mathematics — every network address, subnet mask, broadcast address, and usable host range shown is computed from your actual inputs, not a generic sizing table. It is a planning calculation, not a deployed configuration: verify the output against your organization's actual routing and firewall design before implementing it.
FAQ
Common Questions
How does this tool decide subnet sizes?
You enter the number of usable hosts each segment needs, and the calculator computes the smallest CIDR block that fits that count (accounting for the reserved network and broadcast addresses), using real IPv4 subnet math — not a lookup table of generic recommendations.
What allocation order does it use, and why?
It allocates using VLSM (Variable Length Subnet Masking): your largest host requirement is placed first, then progressively smaller ones, each aligned to its own size boundary. This packing order minimizes wasted address space compared to allocating in an arbitrary order.
Does this tool calculate exact subnet ranges or CIDR blocks for me?
Yes. For each segment you enter, it returns the actual network address, CIDR prefix, subnet mask, broadcast address, and usable host range — computed from your parent network, not a generic sizing guideline. Always verify the output against your actual routing and firewall design before deploying it.
What happens if my segments don't fit in the parent network?
The calculator will show a clear error identifying which segment doesn't fit, rather than silently generating overlapping or invalid ranges. Reduce a host count, remove a segment, or choose a larger parent network (e.g. move from a /24 to a /16) to resolve it.
Operational Support
Need help designing your addressing plan?
IT KORR can help you build a documented, conflict-free addressing standard across every site.
No commitment required — we respond within one business day.