Link Aggregation Throughput Calculator
Estimate the combined throughput of several links bonded together with LACP, EtherChannel or a port channel. Enter how many links are in the bundle, the speed of each and an efficiency factor, and the tool returns the realistic aggregate, the theoretical maximum and the single-flow limit.
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How to use this calculator
- Enter the number of physical links in the aggregation group and the speed of each link in Gbps (all members should be the same speed).
- Optionally adjust the efficiency percentage (default 90) to allow for framing overhead and imperfect load-balancing.
- Read the aggregate throughput, and note the single-flow limit — the most any one connection can use.
How it works
The theoretical maximum is just the number of links multiplied by the per-link speed. The aggregate throughput multiplies that by an efficiency factor (default 90%) to allow for real-world overhead and the fact that traffic rarely hashes perfectly evenly across the members. Link aggregation balances traffic per flow — a hash of the addresses/ports picks one member link for each conversation — so it raises total capacity across many flows but never speeds up a single connection.
Worked example
Worked example. Four 10 Gbps links at 90% efficiency: theoretical maximum = 4 × 10 = 40 Gbps, aggregate = 40 × 0.90 = 36 Gbps. But a single large transfer is still capped at one link's 10 Gbps.
Common mistakes
- Expecting one big transfer to run at the aggregate speed — a single flow is pinned to one member link, so it maxes out at the per-link speed, not the bundle total.
- Mixing link speeds in one bundle — most implementations expect equal-speed members; a slower member can drop out or skew the hashing.
- Ignoring the hashing policy — if all your traffic goes to one destination IP, a src-dst-ip hash may send it all down a single link, wasting the other members.
Frequently asked questions
Why can't link aggregation speed up a single download?
Aggregation load-balances whole flows, not individual packets, to avoid reordering. Every packet of one TCP/UDP connection hashes to the same member link, so that connection can only ever use one link's bandwidth. You need multiple parallel flows to benefit from the combined capacity.
What efficiency figure should I use?
90% is a reasonable default for framing overhead and typical hashing imbalance. If your traffic is many small, well-distributed flows you can use a higher value; if it is a few large flows to similar destinations, real throughput can be much lower because the hash concentrates them on one or two links.
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Tip: Enter any known values to calculate the remaining results.
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