Bandwidth Utilization Calculator
Calculate link utilization percentage from observed throughput against link capacity.
Inputs
Link Utilization %
42.00%
Status
Healthy
Remaining Headroom (Mbps)
580.0
Step by step
Values used
Actual Throughput (Mbps) = 420; Link Capacity (Mbps) = 1,000
Utilization percentage
util% = actual_bps / link_capacity_bps × 100
Link Utilization %
= 42.00
Status
= Healthy
Remaining Headroom (Mbps)
= 580.0
How it works
Bandwidth utilization expresses observed throughput as a fraction of the link's total rated capacity, giving a quick saturation signal independent of the absolute traffic volume — 420 Mbps means very different things on a 1 Gbps link (42%, comfortable) versus a 500 Mbps link (84%, elevated). Sustained utilization above roughly 70-80% on shared links typically starts introducing queuing delay and jitter even before hard packet loss occurs, since bursty traffic patterns mean average utilization understates peak instantaneous demand.
Formula
Utilization percentage
util% = actual_bps / link_capacity_bps × 100
- R_{actual}
- actual throughput
- R_{capacity}
- link capacity
Frequently Asked Questions
How do I measure actual throughput on a Linux interface?
`sar -n DEV 1` or `ifstat` show live per-interface rx/tx rates; `cat /proc/net/dev` gives cumulative byte counters you can sample twice and divide by the elapsed time for an average rate over that interval.
Why does utilization matter more than raw throughput numbers?
Raw throughput without context doesn't reveal whether a link is comfortably provisioned or about to become a bottleneck — utilization normalizes for link speed, making it directly comparable across links of different capacities and a better trigger for capacity-planning alerts.
Is 100% utilization always bad?
Brief spikes to 100% during legitimate bursts are normal and not necessarily harmful, but sustained 100% utilization means the link is the bottleneck for all traffic crossing it, causing queuing delay, increased jitter, and eventually tail-drop packet loss once buffers fill.