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VPN Throughput Calculator

Work out how many Site-to-Site VPN tunnels and ECMP connections your throughput target needs, and what they cost.

About VPN Throughput Calculator

A Site-to-Site VPN tunnel carries roughly 1.25 Gbps regardless of the instance sizes behind it, because the limit is in the VPN endpoint itself. Each VPN connection provides two tunnels, but attached to a virtual private gateway only one carries traffic — the second is standby. Attaching to a Transit Gateway with ECMP enabled lets both tunnels, and tunnels across several connections, be active at once, so aggregate throughput scales in 1.25 Gbps steps rather than being capped. Assuming a VPN will grow with your instance bandwidth is the classic migration mistake; past a couple of gigabits the answer is ECMP over a Transit Gateway or a move to Direct Connect.

Formula

VPN Throughput

usable per tunnel = tunnel capacity × utilisation target; tunnels = ceil(required ÷ usable per tunnel); connections = ceil(tunnels ÷ 2).

2
Tunnels per VPN connection, both active only with ECMP
tunnel capacity
About 1.25 Gbps for a Site-to-Site VPN tunnel
utilisation target
Headroom you leave on each tunnel

Worked example

With the default values below, VPN Throughput Calculator returns Active Tunnels Needed of 5. Change any input above and every figure here is recalculated in your browser.

Inputs used

Throughput requiredminimum 1 Mbps
4,000 Mbps
Throughput per tunnelaccepts 0.1–5 Gbps
1.25 Gbps
Target tunnel utilisationaccepts 10–100 %
70 %
Price per VPN connection-houraccepts 0–2 USD
0.05 USD
Billable hours per monthaccepts 1–744 hours
730 hours

Results

Active Tunnels Needed
5
VPN Connections to Provision
3
Usable Throughput per Tunnel
875 Mbps
Aggregate Throughput Delivered
4,375 Mbps
Monthly VPN Charges
$109.50
ECMP Requirement
Needs ECMP over a Transit Gateway to use 5 tunnels at once

Step by step

  1. 1Values used
  2. 2VPN Throughput
  3. 3Active Tunnels Needed= 5
  4. 4VPN Connections to Provision= 3
  5. 5Usable Throughput per Tunnel= 875 Mbps
  6. 6Aggregate Throughput Delivered= 4,375 Mbps
  7. 7Monthly VPN Charges= 109.50
  8. 8ECMP Requirement= Needs ECMP over a Transit Gateway to use 5 tunnels at once

Assumptions and limits

  • The result is derived only from the 5 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

How is VPN Throughput calculated?

usable per tunnel = tunnel capacity × utilisation target; tunnels = ceil(required ÷ usable per tunnel); connections = ceil(tunnels ÷ 2). A Site-to-Site VPN tunnel carries roughly 1.25 Gbps regardless of the instance sizes behind it, because the limit is in the VPN endpoint itself. Each VPN connection provides two tunnels, but attached to a virtual private gateway only one carries traffic — the second is standby. Attaching to a Transit Gateway with ECMP enabled lets both tunnels, and tunnels across several connections, be active at once, so aggregate throughput scales in 1.25 Gbps steps rather than being capped.

Why does VPN Throughput matter?

Assuming a VPN will grow with your instance bandwidth is the classic migration mistake; past a couple of gigabits the answer is ECMP over a Transit Gateway or a move to Direct Connect.

What values do I need to enter?

This calculator takes 5 inputs: Throughput required, Throughput per tunnel, Target tunnel utilisation, Price per VPN connection-hour, Billable hours per month. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

Why does one flow never exceed 1.25 Gbps even with ECMP?

ECMP hashes on the flow tuple, so a single TCP connection always pins to one tunnel. Aggregate throughput scales with the number of tunnels, but per-flow throughput stays at the single-tunnel ceiling — parallel connections are the only way to use the extra capacity.

Is a VPN cheaper than Direct Connect?

For low volumes usually yes, since a VPN connection costs a few cents per hour plus standard data transfer out. Direct Connect wins on consistent latency and on per-GB transfer rates once volume is high, so compare with the Direct Connect Bandwidth Calculator and confirm current prices with AWS.

Related Calculators

VPN Throughput Calculator – Calculate Active Tunnels Needed