Branch Bandwidth Calculator
Estimate required branch office WAN bandwidth from user count, per-user usage, and concurrency.
Inputs
Typical sustained need per user during active use (varies widely with app mix, e.g. video conferencing needs more)
Percentage of users actively consuming bandwidth at the same time (peak busy period)
Required Bandwidth
75.0Mbps
Recommended Link Size (with 20% headroom)
90.0Mbps
Concurrent Active Users at Peak
35
Step by step
Values used
Number of Users = 50; Bandwidth per Active User = 2 Mbps; Concurrency = 70; Fixed Overhead (VoIP, monitoring, background traffic) = 5 Mbps
Required bandwidth
bw = users × concurrency% × per_user_Mbps + overhead
Required Bandwidth
= 75.0 Mbps
Recommended Link Size (with 20% headroom)
= 90.0 Mbps
Concurrent Active Users at Peak
= 35
How it works
Sizing a branch WAN link for every user's peak simultaneous demand would be wasteful, since not everyone is actively using the network at once — concurrency models the realistic peak busy-period usage (typically 60-80% for office environments) rather than the theoretical maximum. Fixed overhead accounts for always-on traffic like VoIP signaling, network monitoring, and background application traffic that doesn't scale directly with active user count. A headroom margin on top of the calculated requirement absorbs traffic bursts without saturating the link.
Formula
Required bandwidth
bw = users × concurrency% × per_user_Mbps + overhead
Frequently Asked Questions
What concurrency percentage should I use?
70-80% is a common planning figure for general office use, but bursty applications (all-hands video calls, backup windows) can push effective concurrency toward 100% for short periods — if those peak windows matter for your SLA, size for them explicitly rather than relying on an average concurrency assumption.
Why add 20% headroom on top of the calculated requirement?
Sizing a link exactly to calculated peak demand leaves no margin for traffic bursts, new application rollouts, or growth — a 20% headroom buffer is a common rule of thumb to avoid an under-provisioned link degrading user experience the moment usage patterns shift slightly.
How does video conferencing change per-user bandwidth needs?
Significantly — a voice call may need under 100 Kbps, but HD video conferencing commonly needs 1.5-3+ Mbps per active participant (more for group calls with multiple video tiles), so a branch with heavy video conferencing use should raise the per-user Mbps input well above a voice/web-browsing baseline.