SD-WAN Path Selection Calculator
Score two SD-WAN paths on latency, jitter and loss to see which one the policy engine should prefer.
About SD-WAN Path Selection Calculator
Each impairment is weighted by how badly it damages interactive traffic, then subtracted from a perfect 100. Loss carries the heaviest weight because a single lost packet triggers a retransmit and a TCP window collapse, while a few extra milliseconds of latency are usually invisible. SD-WAN policies steer on thresholds, and a scoring model makes it obvious whether a brownout on the primary path is bad enough to justify moving voice onto the broadband circuit.
Formula
SD-WAN Path Selection
score = 100 − (0.6 × latency ms + 2.5 × jitter ms + 30 × loss %), clamped to 0–100; the higher score wins.
- 30
- Penalty per percent of packet loss — loss hurts far more than delay
- 0.6
- Penalty per millisecond of one-way latency
Worked example
With the default values below, SD-WAN Path Selection Calculator returns Preferred Path of Path A. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Path A latencyaccepts 0–1,000 ms
- 18 ms
- Path A jitteraccepts 0–200 ms
- 3 ms
- Path A packet lossaccepts 0–20 %
- 0.1 %
- Path B latencyaccepts 0–1,000 ms
- 45 ms
- Path B jitteraccepts 0–200 ms
- 12 ms
- Path B packet lossaccepts 0–20 %
- 0.8 %
Results
- Preferred Path
- Path A
- Path A Score
- 78.7 /100
- Path B Score
- 19.0 /100
- Score Margin
- 59.7
- Quality of the Winner
- B — Good
Step by step
- 1Values used
- 2SD-WAN Path Selection
- 3Preferred Path= Path A
- 4Path A Score= 78.7 /100
- 5Path B Score= 19.0 /100
- 6Score Margin= 59.7
- 7Quality of the Winner= B — Good
Assumptions and limits
- The result is derived only from the 6 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 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
How is SD-WAN Path Selection calculated?
score = 100 − (0.6 × latency ms + 2.5 × jitter ms + 30 × loss %), clamped to 0–100; the higher score wins. Each impairment is weighted by how badly it damages interactive traffic, then subtracted from a perfect 100. Loss carries the heaviest weight because a single lost packet triggers a retransmit and a TCP window collapse, while a few extra milliseconds of latency are usually invisible.
Why does SD-WAN Path Selection matter?
SD-WAN policies steer on thresholds, and a scoring model makes it obvious whether a brownout on the primary path is bad enough to justify moving voice onto the broadband circuit.
What values do I need to enter?
This calculator takes 6 inputs: Path A latency, Path A jitter, Path A packet loss, Path B latency, Path B jitter, Path B packet loss. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.