Enter Network Inputs
Example Data Table
These rows are sample planning cases for quick interpretation.
| Scenario | Capacity | Avg In / Out | Peak In / Out | Reserved | Overhead | Mode | Projected Peak Utilization |
|---|---|---|---|---|---|---|---|
| Core Uplink | 1 Gbps | 320 / 280 Mbps | 760 / 640 Mbps | 50 Mbps | 7% | Full Duplex | 98.93% |
| Branch WAN | 200 Mbps | 70 / 52 Mbps | 145 / 120 Mbps | 10 Mbps | 6% | Full Duplex | 89.31% |
| Shared Legacy Segment | 100 Mbps | 18 / 16 Mbps | 42 / 35 Mbps | 5 Mbps | 8% | Half Duplex | 105.72% |
Formula Used
1. Effective Capacity
Effective Capacity = Link Capacity − Reserved Bandwidth
2. Usable Capacity
Usable Capacity = Effective Capacity × (1 − Protocol Overhead ÷ 100)
3. Governing Traffic Load
In full-duplex mode, Governing Load = max(Inbound, Outbound)
In half-duplex mode, Governing Load = Inbound + Outbound
4. Average Utilization
Average Utilization (%) = Average Governing Load ÷ Usable Capacity × 100
5. Peak Utilization
Peak Utilization (%) = Peak Governing Load ÷ Usable Capacity × 100
6. Projected Peak Load
Projected Peak Load = Peak Governing Load × (1 + Growth Rate ÷ 100)
7. Projected Peak Utilization
Projected Peak Utilization (%) = Projected Peak Load ÷ Usable Capacity × 100
8. Headroom
Headroom = Usable Capacity − Traffic Load
9. Average Transferred Data
Average Data = (Average Inbound + Average Outbound) × Monitoring Time ÷ 8
10. Recommended Capacity at Target
Recommended Capacity = Projected Peak Load ÷ (Target Utilization ÷ 100)
How to Use This Calculator
- Enter the physical or logical link capacity and choose its unit.
- Select full duplex for separate send and receive paths, or half duplex for shared media.
- Provide average inbound and outbound traffic from monitoring tools or flow records.
- Enter peak traffic values from observed busy periods, not theoretical limits.
- Add reserved bandwidth for QoS, voice, storage replication, or protected services.
- Set protocol overhead to reflect framing, tunneling, encapsulation, or transport inefficiency.
- Enter a growth rate to estimate future peak demand.
- Choose a target utilization threshold that matches your design policy.
- Use the results table, graph, CSV, and PDF exports for planning or documentation.
FAQs
1. What does network utilization measure?
It measures how much of a link’s usable bandwidth is being consumed by actual traffic. Higher percentages mean less spare capacity and a greater chance of congestion during bursts.
2. Why is usable capacity lower than link capacity?
Usable capacity is reduced by reserved bandwidth and protocol overhead. Tunnels, encapsulation, headers, and service reservations all lower the bandwidth available to application traffic.
3. Why does full duplex use the busier direction?
Full-duplex links send and receive independently. Saturation usually occurs in the direction carrying more traffic, so the busier side is the best indicator of utilization risk.
4. When should I worry about utilization above 70%?
Many teams flag sustained utilization above 70% because bursts, microbursts, and short-lived traffic spikes can still cause queues, delay, and dropped packets before a link reaches 100%.
5. What is headroom in this calculator?
Headroom is the remaining usable bandwidth after current or projected traffic is subtracted. Positive headroom means spare capacity. Negative headroom means the design target or usable capacity is exceeded.
6. Why include projected growth?
Growth modeling prevents under-sizing. A link that looks healthy today may become a bottleneck soon if traffic is increasing because of new users, backups, cloud workloads, or replication jobs.
7. Can I use this for wireless, VPN, or tunneled links?
Yes. It is especially useful there because overhead and reserved capacity often matter more. Just use realistic traffic values and appropriate overhead assumptions for the specific technology.
8. When should I upgrade capacity?
Consider upgrading when projected peak utilization nears your policy threshold, projected headroom turns negative, or the recommended capacity is materially higher than the existing link.