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Calcrivo

VPN Bandwidth Calculator

Size the WAN circuit a remote-access or site-to-site VPN needs once encryption and encapsulation overhead is added.

Inputs

users
kbps
%
bytes

Tunnel Bandwidth Required

41.47Mbps

Useful Payload

38.40Mbps

Encapsulation Overhead

8.00%

Circuit Size with 25% Headroom

51.84Mbps

Concurrent Users

150

Step by step

  1. Values used

    Remote users = 500 users; Per-user throughput = 256 kbps; Concurrent users = 30 %; Average packet size = 700 bytes; VPN encapsulation = IPsec ESP tunnel, AES-GCM (56 B)

  2. VPN Bandwidth

    tunnel Mbps = concurrent users × per-user rate × (packet size + encapsulation bytes) ÷ packet size.

  3. Tunnel Bandwidth Required

    = 41.47 Mbps

  4. Useful Payload

    = 38.40 Mbps

  5. Encapsulation Overhead

    = 8.00

  6. Circuit Size with 25% Headroom

    = 51.84 Mbps

  7. Concurrent Users

    = 150

How it works

Concurrency turns a user population into a simultaneous load, and the ratio (payload + header) ÷ payload converts clear-text demand into ciphertext on the wire. Small packets pay the fixed ESP header far more often, so voice-heavy traffic inflates more than bulk file transfer. VPN circuits are billed on the encrypted rate, not the payload rate, so sizing on application throughput alone under-provisions the link by 8–15% and shows up as tunnel drops at peak.

Formula

VPN Bandwidth

tunnel Mbps = concurrent users × per-user rate × (packet size + encapsulation bytes) ÷ packet size.

per-user rate
Average application throughput per active user
encapsulation bytes
Bytes the VPN adds to every packet (56–73 for IPsec ESP)

Frequently Asked Questions

How is VPN Bandwidth calculated?

tunnel Mbps = concurrent users × per-user rate × (packet size + encapsulation bytes) ÷ packet size. Concurrency turns a user population into a simultaneous load, and the ratio (payload + header) ÷ payload converts clear-text demand into ciphertext on the wire. Small packets pay the fixed ESP header far more often, so voice-heavy traffic inflates more than bulk file transfer.

Why does VPN Bandwidth matter?

VPN circuits are billed on the encrypted rate, not the payload rate, so sizing on application throughput alone under-provisions the link by 8–15% and shows up as tunnel drops at peak.

What values do I need to enter?

This calculator takes 5 inputs: Remote users, Per-user throughput, Concurrent users, Average packet size, VPN encapsulation. 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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