Networking · How-to
How to Test Your Internet Speed Accurately
"My internet is slow" is one of the vaguest complaints in tech. A speed test converts that feeling into three numbers — download, upload, latency — but only if you run it correctly. This guide covers how speed tests actually work, how to get consistent results, and what the numbers mean.
What a speed test measures
- Download speed (Mbps) — how fast data comes to you.
- Upload speed (Mbps) — how fast data leaves you.
- Latency / ping (ms) — round-trip time to the test server.
- Jitter (ms) — variation in latency; high jitter breaks calls even with low ping.
- Packet loss (%) — percentage of packets that don't arrive. Anything over 1% is a real problem.
How to run an accurate test
- Close everything else. Pause downloads, cloud sync, streaming, and quit background apps.
- Test wired if you can. Ethernet removes Wi-Fi variability. Wi-Fi tests measure your Wi-Fi, not your ISP.
- Test at multiple times of day. Peak evening hours often show congestion your daytime test misses.
- Test to multiple servers. A single server can be overloaded or geographically distant.
- Run three tests and take the median. Individual runs are noisy.
Which speed test should you use?
- Ookla Speedtest — the industry standard. Servers everywhere.
- fast.com — run by Netflix; measures against their CDN, so it's a good real-world proxy for streaming.
- Cloudflare speed test (speed.cloudflare.com) — thorough, includes bufferbloat and packet loss.
- Your ISP's tester — usually flattering; use for baseline only.
Reading the results
| Speed | Comfortable for |
|---|---|
| 10 Mbps | HD streaming, 1 device |
| 25 Mbps | 4K streaming, 2–3 devices |
| 100 Mbps | Family of 4, WFH, gaming |
| 500 Mbps+ | Multiple 4K streams, large downloads, creators |
Common reasons speed tests underperform
- Old router. Wi-Fi 5 (802.11ac) caps around 500 Mbps in practice. If you pay for gigabit, you need Wi-Fi 6 or Ethernet.
- Distance and walls. Every wall and every 3 m halves Wi-Fi throughput.
- 2.4 GHz overcrowding. Prefer 5 GHz or 6 GHz for anything speed-sensitive.
- Old Ethernet cable. Cat 5 caps at 100 Mbps. Use Cat 5e or better.
- ISP throttling. Some ISPs cap specific protocols or streaming services.
- DNS lag. Slow DNS makes pages feel slow even when raw speed is fine. Test with Toolzer's DNS Speed Test.
When to call your ISP
Run three wired tests, at different times of day, to different servers. If the median is consistently below 70% of your plan's advertised speed, you have a legitimate complaint. Bring screenshots — ISP support respects data more than adjectives.
Try it on Toolzer
- Ping / Latency Test — measure round-trip time to any host.
- DNS Speed Test — compare public DNS resolvers.
- DNS Leak Test — verify your VPN isn't leaking DNS.
Frequently asked questions
Why does my speed test vary so much?+
Wi-Fi congestion, distance to router, background downloads, VPN overhead, and server distance all affect results. Run three tests to different servers and take the median.
What's a good internet speed?+
For 4K streaming, 25 Mbps down; for video calls, 5 Mbps up. Gaming needs low latency (<50 ms) more than raw speed. A family of four comfortably uses 100 Mbps.
Why is my Wi-Fi slower than my plan?+
Wi-Fi loses 30–50% of the wired throughput at typical distances. To test your ISP, plug into the router with Ethernet — that's the number your ISP promised.
What's the difference between download and upload?+
Download is data coming to you (streaming, browsing). Upload is data leaving you (video calls, backups, cloud sync). Most home connections are asymmetric — download is much faster than upload.
What is ping / latency?+
The round-trip time in milliseconds for a small packet. Under 30 ms is excellent; over 100 ms you'll notice lag in gaming and video calls.
Should I test with or without VPN?+
Test both. VPNs typically cost 10–30% throughput. If the VPN result is much slower, try a closer VPN server.