BT Speed Test (UK) — Real Speeds & Fixes

On BT, the number that matters is the Minimum Guaranteed Speed printed on your contract, not the headline figure. If a wired test into the Smart Hub sits below that figure and stays there, BT has 30 days to fix it under the Ofcom Broadband Speeds Code before you can exit the contract penalty-free.

Check which product you're on first: FTTC (copper from a street cabinet) is distance-limited and caps around 67 Mbps down / 20 Mbps up. Full Fibre (FTTP) should deliver close to plan on a wired test, and anything well below it is usually Wi-Fi.

BT is the UK's largest residential ISP, running on the Openreach network. Plans range from legacy ADSL to 1.6 Gbps Full Fibre. The biggest factor in your real-world speed is which Openreach product you actually have.

Whether you can get Full Fibre at all depends on the exact address, not the postcode: Openreach builds street by street, and two neighbouring properties can be on different products. Your available speeds also depend on the length of copper to your cabinet if FTTP has not reached you yet. Check the address on BT's own availability checker before assuming an upgrade is possible.

Plans and realistic speeds

Fibre Essential 36 Mbps (FTTC): 30-38 Mbps down, 8-10 Mbps up
Fibre 2 / 67 Mbps (FTTC): 55-67 Mbps down, 18-20 Mbps up
Full Fibre 100: 95-110 Mbps both directions
Full Fibre 500: 490-540 Mbps both directions
Full Fibre 900 / 1.6 Gbps: 880-940 Mbps and 1.4-1.6 Gbps wired

Common issues and how to fix them

Speeds far below the FTTC estimate: Distance from the cabinet matters. Run a wired test directly into the Smart Hub. If still low, raise a fault, Openreach can re-jumper your line at the cabinet.
Smart Hub Wi-Fi is the bottleneck: Switch to Smart Hub 2 or add a Wi-Fi 6 mesh (Plume, Eero, Deco). Wi-Fi often loses 30-40% on FTTP plans above 300 Mbps.
BT Sport / streaming buffering: Usually upstream congestion at the BT exchange in evening peak. Test at noon and 9 PM, if the gap is large, you've hit it.
Speed dropped after a line fault was 'fixed': Openreach DLM (Dynamic Line Management) lowers your sync rate after repeated errors and raises it back slowly. Leave the hub powered on continuously for 72 hours before retesting.

Typical latency

Within UK to London PoP: 4-12 ms
London to Frankfurt: 15-25 ms
London to New York: 70-85 ms
London to Singapore: 170-200 ms

Wired vs Wi-Fi checks

Plug directly into a yellow LAN port on the Smart Hub with a Cat5e or better cable and run three tests; take the median.
Repeat on Wi-Fi standing in the same room as the hub, then again where you actually use the connection.
If wired matches the plan and Wi-Fi doesn't, the fault is coverage, not the line — BT Complete Wi-Fi discs or any Wi-Fi 6 mesh fixes it.
If wired is also low, reboot the hub once, retest, and only then raise a fault so Openreach sees a clean line reading.

Reading your result against your plan

FTTC (Fibre Essential / Fibre 2): sync rate is set by the copper length from your cabinet, so a stable result 10-15% under the headline figure is normal and not a fault by itself. Compare against the Minimum Guaranteed Speed instead.
Full Fibre (FTTP): a wired result under about 80% of plan is worth reporting, because the fibre path is not distance-limited the way copper is.
Full Fibre 900 and 1.6 Gbps: a single 1 Gbps Ethernet port physically caps you near 940 Mbps. To see above that you need a 2.5 GbE or faster adapter on the device you test from.
Upload on FTTC is the hard ceiling for cloud backup and video calls: roughly 10 Mbps on 36 Mbps plans and 20 Mbps on 67 Mbps plans, no matter how quiet the line is.