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Calcrivo

SD-WAN Link Calculator

Size the SD-WAN circuit for a branch from user count, concurrency, growth and overlay overhead.

Inputs

users
kbps
%
%
%

Bandwidth Required

29.16Mbps

Recommended Circuit Tier

50Mbps

Utilisation at That Tier

58.3%

Concurrent Users

54

Order This Service

50 Mbps circuit

Step by step

  1. Values used

    Users at the site = 120 users; Busy-hour rate per user = 400 kbps; Concurrent users = 45 %; Growth allowance = 25 %; Overlay and tunnel overhead = 8 %

  2. SD-WAN Link

    required = users × concurrency × per-user rate × (1 + growth) × (1 + overlay overhead), rounded up to the next carrier tier.

  3. Bandwidth Required

    = 29.16 Mbps

  4. Recommended Circuit Tier

    = 50 Mbps

  5. Utilisation at That Tier

    = 58.3

  6. Concurrent Users

    = 54

  7. Order This Service

    = 50 Mbps circuit

How it works

The busy-hour rate is applied only to concurrent users, then inflated for growth over the contract term and for tunnel encapsulation. Rounding up to a carrier tier turns the figure into something you can actually order. Branch circuits are contracted for two or three years, so a 20% sizing error is either a permanent overspend or a permanent congestion ticket queue.

Formula

SD-WAN Link

required = users × concurrency × per-user rate × (1 + growth) × (1 + overlay overhead), rounded up to the next carrier tier.

concurrency
Fraction of the population active in the busy hour
overlay overhead
Extra bytes from IPsec, GRE or VXLAN on the SD-WAN fabric

Frequently Asked Questions

How is SD-WAN Link calculated?

required = users × concurrency × per-user rate × (1 + growth) × (1 + overlay overhead), rounded up to the next carrier tier. The busy-hour rate is applied only to concurrent users, then inflated for growth over the contract term and for tunnel encapsulation. Rounding up to a carrier tier turns the figure into something you can actually order.

Why does SD-WAN Link matter?

Branch circuits are contracted for two or three years, so a 20% sizing error is either a permanent overspend or a permanent congestion ticket queue.

What values do I need to enter?

This calculator takes 5 inputs: Users at the site, Busy-hour rate per user, Concurrent users, Growth allowance, Overlay and tunnel overhead. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

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