VPN Throughput Calculator

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.

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.

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.

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.

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.