Branch Bandwidth
Calculate required WAN bandwidth for a branch office based on users and application mix.
About Branch Bandwidth
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
Worked example
With the default values below, Branch Bandwidth returns Required Bandwidth of 75.0. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Number of Usersminimum 1
- 50
- Bandwidth per Active Userminimum 0.1 Mbps
- 2 Mbps
- Concurrencyaccepts 1–100
- 70
- Fixed Overhead (VoIP, monitoring, background traffic)minimum 0 Mbps
- 5 Mbps
Results
- Required Bandwidth
- 75.0 Mbps
- Recommended Link Size (with 20% headroom)
- 90.0 Mbps
- Concurrent Active Users at Peak
- 35
Step by step
- 1Values used
- 2Required bandwidth
- 3Required Bandwidth= 75.0 Mbps
- 4Recommended Link Size (with 20% headroom)= 90.0 Mbps
- 5Concurrent Active Users at Peak= 35
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or fees or charges into account.
- Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
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.