WAN Capacity Planning Calculator

Enter WAN Planning Inputs

The page uses a stacked layout, while the calculator form switches to three columns on large screens, two on medium screens, and one on mobile.

Number of Sites

Total branches, campuses, or offices sharing WAN resources.

Average Users per Site

Use typical connected staff, not total directory accounts.

Peak Concurrency (%)

Percent of users expected to be active simultaneously.

Interactive kbps per User

Typical business traffic like web, ERP, email, and SaaS.

Real-Time User Share (%)

Share of concurrent users on voice or video sessions.

Real-Time kbps per User

Per-user requirement for conferencing, voice, or media flows.

Protocol Overhead (%)

Allow for headers, encapsulation, encryption, and retransmissions.

Burst Margin (%)

Extra headroom for spikes, backups, updates, and busy windows.

Annual Growth (%)

Expected traffic growth rate over one year.

Planning Horizon (Months)

How far ahead the design should remain serviceable.

Target Utilization (%)

Lower values leave more operating margin under congestion.

Redundancy Profile

Choose whether the design includes additional resilient capacity.

Business Hours per Day

Used to estimate approximate monthly transferred data volume.

Working Days per Month

Use all days for always-on operations.

Example Data Table

The table below shows one sample planning scenario and the calculated sizing outcome.

Sites	Users / Site	Peak Concurrency	Interactive kbps	Real-Time Share	Real-Time kbps	Overhead	Burst	Growth	Months	Utilization	Redundancy	Recommended Total	Recommended Per Site
12	85	32%	180	24%	320	15%	20%	18%	18	65%	Dual active paths	256.14 Mbps	21.34 Mbps

Formula Used

1. Total users
Total Users = Sites × Users per Site

2. Concurrent users
Concurrent Users = Total Users × Peak Concurrency %

3. Payload throughput
Interactive Mbps = Interactive Users × Interactive kbps ÷ 1000
Real-Time Mbps = Real-Time Users × Real-Time kbps ÷ 1000
Payload Mbps = Interactive Mbps + Real-Time Mbps

4. Adjusted traffic
Overhead Mbps = Payload Mbps × (1 + Overhead %)
Burst Mbps = Overhead Mbps × (1 + Burst Margin %)

5. Forecast demand
Growth Multiplier = (1 + Annual Growth %) ^ (Planning Months ÷ 12)
Forecast Mbps = Burst Mbps × Growth Multiplier

6. Engineered and resilient capacity
Engineering Need = Forecast Mbps ÷ Target Utilization %
Recommended Total Capacity = Engineering Need × Redundancy Factor
Recommended Per-Site Capacity = Recommended Total Capacity ÷ Sites

How to Use This Calculator

Enter the number of WAN-connected sites and the average users at each site.
Estimate peak concurrency, then separate interactive traffic from real-time sessions.
Add overhead, burst margin, forecast growth, and your preferred utilization target.
Choose a redundancy model that matches your resilience design standard.
Submit the form to see total capacity, per-site sizing, circuit recommendations, and the forecast chart.
Use the CSV and PDF buttons to export the current result set for review, procurement, or design notes.

FAQs

1. What does peak concurrency represent?

Peak concurrency is the share of total users actively consuming WAN bandwidth at the same time. It is more realistic than sizing links for every user being fully active together.

2. Why are interactive and real-time users separated?

Real-time applications usually need steadier bandwidth and lower delay. Splitting them from ordinary business traffic gives a more accurate estimate for capacity planning and QoS-sensitive environments.

3. Should I include protocol overhead?

Yes. Encapsulation, VPN headers, retransmissions, and security controls reduce usable payload efficiency. Adding overhead keeps planned circuits from looking good on paper but failing in production.

4. What is a good target utilization value?

Many teams use 60% to 75% for stable operation. Lower targets add more headroom, while higher targets increase risk during bursts, failovers, or growth beyond the forecast.

5. How should I choose a redundancy profile?

Match it to your architecture. No extra path suits best-effort links, while dual-active or active-passive models better reflect environments needing stronger availability during outages or maintenance.

6. Does this calculator size internet, MPLS, and SD-WAN equally?

The core traffic math is neutral, but transport behavior differs. You should still review latency, packet loss, path diversity, and vendor shaping policies before finalizing procurement.

7. Why does the tool recommend standard circuit tiers?

Providers usually sell standardized bandwidth tiers. The recommendation rounds your computed demand up to a practical purchase size, helping you compare options faster.

8. Can I use this for future branch expansion?

Yes. Increase site counts, users, or growth assumptions to model expansion. The planning horizon and forecast logic help you test whether today’s design still supports tomorrow’s demand.