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VPN Throughput Overhead Calculator

Work out vpn throughput overhead instantly with clear inputs, formula shown and shareable results.

About VPN Throughput Overhead Calculator

A VPN tunnel adds an outer IP header, the security protocol header, an initialisation vector and an authentication tag — roughly 57 bytes for IPsec with AES-GCM and about 32 for WireGuard. Effective throughput is the lower of the link and the crypto engine, multiplied by tunnel efficiency, which is why VPN appliances are rated separately for encrypted throughput.

Formula

VPN throughput

efficiency = payload / (payload + tunnel overhead); effective = min(link, crypto throughput) x efficiency

Worked example

With the default values below, VPN Throughput Overhead Calculator returns Effective application throughput of 480.44. Change any input above and every figure here is recalculated in your browser.

Inputs used

Application payload per packetaccepts 1–9,000 bytes
1,400 bytes
VPN typeone of IPsec tunnel mode with AES-GCM, IPsec with AES-CBC and HMAC, WireGuard, OpenVPN over UDP
IPsec tunnel mode with AES-GCM
Link bandwidthminimum 0.001 Mbps
500 Mbps
Device crypto throughputminimum 0.001 Mbps
800 Mbps

Results

Effective application throughput
480.44 Mbps
Tunnel overhead per packet
57 bytes
Tunnel efficiency
96.09%
Binding constraint
Link bandwidth

Step by step

  1. 1Values used
  2. 2VPN throughput
  3. 3Effective application throughput= 480.44 Mbps
  4. 4Tunnel overhead per packet= 57 bytes
  5. 5Tunnel efficiency= 96.09
  6. 6Binding constraint= Link bandwidth

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 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 is WireGuard more efficient?

It has a compact fixed header and a single modern cipher suite with no negotiation, so both per-packet overhead and CPU cost are lower than IPsec's.

Does hardware offload change the picture?

Substantially. AES-NI and dedicated crypto engines move the bottleneck back to the link, which is why crypto throughput should always be checked against the appliance datasheet.

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