Why is my speed test slower than my plan?

Most results below plan speed come from the measurement — Wi-Fi, the device's network port, the cabling, or the test server — but if a proper wired test is well short, we want to hear about it.

We'd rather explain this than argue with it. Here's the honest list, roughly in order of how often it's the answer.

Wi-Fi overhead. Wi-Fi's advertised rates are radio rates, not throughput. Real-world results are a fraction of them, and they drop with distance, walls, interference, and the number of devices sharing the channel. 2.4 GHz is worse than 5 or 6 GHz. A Wi-Fi test almost never shows the full line.

Your device's network port. A 1 Gb Ethernet port tops out near 940 Mbps once Ethernet, IP, and TCP overhead are subtracted. On a 2 Gb or 10 Gb plan that port is the ceiling — the line isn't slow, the adapter can't count that high. Older laptops, USB dongles, and cheap switches all cap out somewhere.

Cabling and jacks. A damaged cable, a badly crimped end, or an in-wall jack punched down on only two pairs will silently negotiate 100 Mbps and stay there. Swap the cable before you blame anything else.

The test server. You're testing to someone else's server over someone else's network. A distant, busy, or under-provisioned server will report its own limit as yours. Try a second server before drawing conclusions.

Single stream versus multi-stream. A single TCP connection is limited by latency and window size, and often can't fill a multi-gigabit line on its own. Multi-gig results usually need a test that opens parallel streams.

What is not the explanation: your upload. Every plan is symmetrical — 1 Gig down is 1 Gig up.

If a wired test on hardware that can carry the plan comes back well short, that's a line question, not a measurement question, and we want to see it.

If that didn’t work

Call (617) 693-9434 with your wired result, the device, and the test server you used.

More in Troubleshooting

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• Why is my streaming buffering?
• Why do my video calls and games lag?

Talk to us

Call (617) 693-9434, Monday to Friday 8am–6pm ET, or email [email protected]. We answer within 24 hours, and usually within an hour.

Boston Broadband is a service-area business serving Boston, Brookline and Cambridge, Massachusetts. There is no counter to walk up to — phone, email and your account at myaccount.bostonbroadband.com are the ways in.