Measuring correctly
Is 100 Mbps internet really 100 Mbps? Why tests top out around 94
No, a speed test won't show exactly 100, and that isn't a fault. Every packet on the internet carries headers the wire and protocols need, so a 100 Mbps line carries roughly 94.1 Mbps of usable data even under perfect conditions. In HIZTESTI's measurements from Turkey the footprint of 100 Mbps plans shows up as a clear pile-up between 90 and 100 Mbps.
Why is the ceiling around 94?
A 100 Mbps plan means 100 million bits a second can cross the wire. Not all of those bits are your video or file. Every packet travels with headers saying where it's from, where it's going, its order and whether it arrived intact. Add up the Ethernet, IP and TCP headers and the mandatory gap between packets, and 1448 of every 1538 bytes are left for data.
Speed tests count only your data, because that's the part that does anything for you. The highest reading a 100 Mbps line can reach is therefore about 94.1 Mbps. If you see 93 or 94, your line is running at full capacity.
The same rule applies to every plan: a 50 Mbps line tops out near 47.1 Mbps, and a 1000 Mbps line near 941.5 Mbps.
The footprint of 100 Mbps plans
The footprint of 100 Mbps plans is clear in HIZTESTI's measurements: the 90–100 Mbps band holds 2.34 times as many results as the 100–110 band just above it. When a plan can reach its ceiling, measurements gather right there, around 94. The rest of the distribution is very wide. Half of fixed-line measurements are below 43.5 Mbps and a tenth are below 6.6 Mbps; those include slower plans as well as tests run over Wi-Fi.
If you're well below 90
Protocol overhead is fixed at about six percent. If your 100 Mbps plan shows 70 or 50, the gap is coming from somewhere else. Four causes come up most often:
Wi-Fi is the biggest loss compared with a cable: Why Wi-Fi slows your speed test
The device running the test can be the limit: Your device may be slowing the speed test
Other devices in use at home split your speed: Devices sharing your connection
In the evening the provider's shared capacity fills up: Why the internet slows down in the evening
Measuring your plan's ceiling properly
- Connect your computer to the router with an Ethernet cable. Make sure the cable and your network card support gigabit; an old cable or card can lock the link to 100 Mbps.
- Make sure nothing else at home is downloading, streaming or backing up.
- Keep only the speed test tab open in your browser.
- Run one test at night or in the morning and one in the evening, then compare them.
Background tabs and the other details that matter: How to run a speed test correctly
Run a test first to see where your result sits. Start a speed test
If you have a fiber or gigabit plan, the testing checklist: How to test fiber internet speed
The data in detail: charts and diagrams
How much of a packet is your data?
Distribution of fixed-line download speeds
| Mbps | Share of measurements |
|---|---|
| 0–10 | 14.9% |
| 10–25 | 18.1% |
| 25–35 | 10.2% |
| 35–45 | 8.2% |
| 45–55 | 9.5% |
| 55–75 | 8.2% |
| 75–90 | 6% |
| 90–100 | 6% |
| 100–110 | 2.5% |
| 110–180 | 4.7% |
| 180–200 | 1.8% |
| 200–300 | 3.4% |
| 300–500 | 2.8% |
| 500–900 | 3.1% |
| 900–1000 | 0.7% |
| 1000+ | 0% |
HIZTESTI measurements · 1 Jul – 28 Sep 2026 · fixed line
Frequently asked questions
- What should a speed test show on a 100 Mbps plan?
- At most about 94.1 Mbps on a wired, idle line. The difference comes from the addressing on every packet; it isn't speed you're losing.
- My plan is faster, so why is my test stuck at exactly 100 Mbps?
- Something on the path can't go past 100 Mbps: a network card without gigabit support, an old cable or a 100 Mbps port on the router. Swap the cable and the port and test again.
- I get 60 Mbps over Wi-Fi. Am I being short-changed?
- Probably not. Wi-Fi measures noticeably lower than a cable because of distance, walls and neighbouring networks. Test with a cable before judging your plan.
- What should I do before contacting my provider?
- Run several wired tests on an idle line at different days and times and keep the result links. If results are consistently far below 90, those are your evidence.
Sources
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