Why Is My Result Lower Than My Plan Speed?
Many factors sit between your ISP's advertised speed and what arrives at your device. Here's how to identify which one is causing the gap — and how to fix it.
The most common causes — ranked by frequency
| Cause | How much speed it loses | How to confirm |
|---|---|---|
| Wi-Fi signal weakness | 20–90% loss | Compare Ethernet vs Wi-Fi test |
| Outdated or underpowered router | 10–60% loss | Ethernet direct to modem bypasses router |
| Background device activity | Variable | Check task manager during test |
| ISP congestion (time-dependent) | 10–50% loss evenings/weekends | Run tests at 9 AM vs 9 PM and compare |
| Older network adapter in device | Caps at 100 Mbps on gigabit plans | Check adapter spec in device settings |
| ISP speed throttling | Targeted reduction after data cap | VPN bypass test; compare to plan terms |
| Faulty or degraded coax/phone line | Consistent reduction | Consistent low speed on Ethernet too |
Step 1 — Test on Ethernet first
Connect your laptop or desktop directly to the router with an Ethernet cable and run the test again. If the result on Ethernet matches your plan speed (or comes close), the problem is your Wi-Fi — not your ISP. See the Wi-Fi improvement guide →
If the Ethernet result is also significantly below your plan speed, move to Step 2.
Step 2 — Bypass the router
Connect your device directly to the modem or the ISP's gateway device (if it's a combined modem/router, skip this step). Run the test again. If this produces full plan speed, the router is the bottleneck — it may be too slow to route packets at your plan's speed, or its firmware is out of date.
Step 3 — Check for time-of-day variation
Run tests at 7–9 AM and again at 7–9 PM for two or three days. If results are consistently good in the morning and consistently poor in the evenings, your ISP's network is congested during peak hours. This is an ISP problem, not something you can fix on your end — contact your ISP to report it, or check whether another ISP serves your area with better capacity.
Step 4 — Check for throttling
Some ISPs reduce speeds for specific services (video streaming, P2P) or after you've used a certain amount of data in a billing period. How to detect ISP throttling →
Understanding "up to" plan speeds
ISPs advertise maximum theoretical speeds, not guaranteed speeds. A "100 Mbps" plan means the connection is capable of delivering up to 100 Mbps under ideal conditions. Most regulatory bodies require ISPs to deliver at least 50–80% of advertised speeds during peak hours under fair-use policies. If you're consistently receiving under 50% of your advertised speed on a wired connection, you have grounds to contact your ISP and request investigation.
What "full plan speed" actually means
Even on a perfect connection, your speed test result will be slightly below the raw plan speed due to protocol overhead. TCP/IP headers, TLS encryption overhead, and HTTP framing consume roughly 3–5% of raw bandwidth. A 1000 Mbps (1 Gbps) plan will typically show 920–970 Mbps on a perfect connection — that's expected and normal.