SD-WAN Capacity
Calculate aggregate SD-WAN throughput capacity across multiple underlay links.
About SD-WAN Capacity
SD-WAN combines multiple underlying transport links (MPLS, broadband, LTE/5G, satellite) into one logical connection, but the effective usable capacity is less than the simple sum of link speeds: a path quality factor accounts for real-world loss, jitter, and the SD-WAN controller steering some traffic away from degraded paths, and a fixed control-plane overhead — consumed by encapsulation, path monitoring probes, and orchestration traffic — is subtracted from the total.
Formula
Effective SD-WAN capacity
effective = (sum of link bandwidths × path_quality_factor) − control_overhead
- B_i
- Bandwidth of link i
- q
- Path quality factor (0-1)
- O
- Control-plane overhead
Worked example
With the default values below, SD-WAN Capacity returns Effective SD-WAN Capacity of 175.00. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Link Bandwidths (comma-separated)
- 100, 50, 50
- Average Path Quality Factoraccepts 1–100
- 90
- Control-Plane Overheadminimum 0 Mbps
- 5 Mbps
Results
- Effective SD-WAN Capacity
- 175.00 Mbps
- Raw Aggregate Bandwidth (sum of links)
- 200.00 Mbps
- After Path Quality Factor
- 180.00 Mbps
- Number of Links Combined
- 3
- Control Overhead (% of raw bandwidth)
- 2.50%
Step by step
- 1Values used
- 2Effective SD-WAN capacity
- 3Effective SD-WAN Capacity= 175.00 Mbps
- 4Raw Aggregate Bandwidth (sum of links)= 200.00 Mbps
- 5After Path Quality Factor= 180.00 Mbps
- 6Number of Links Combined= 3
- 7Control Overhead (% of raw bandwidth)= 2.50
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, 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
Why isn't effective SD-WAN throughput just the sum of all link speeds?
Real-world links rarely deliver their full rated speed continuously — congestion, loss, and jitter on broadband or cellular links, plus the SD-WAN controller's own quality-based steering (which shifts traffic away from a degraded path rather than using its full nominal capacity), mean actual usable throughput runs below the simple arithmetic sum.
What consumes SD-WAN control-plane overhead?
Continuous path quality probing (measuring latency/jitter/loss on every link to make steering decisions), tunnel encapsulation headers, and orchestration/telemetry traffic to the SD-WAN controller all consume a small but constant slice of aggregate bandwidth, independent of how much user traffic is flowing.
Does adding more links always increase effective capacity proportionally?
Only if the added links have comparable quality — adding a high-latency, lossy link contributes less usable capacity per Mbps of rated speed than adding another reliable link, since the path quality factor effectively discounts unreliable paths more heavily in real deployments than this simplified average-factor model shows.