What Gap Is Normal?
| Setup | Expected % of plan speed |
|---|---|
| Ethernet direct to modem | 95-100% |
| Ethernet through router | 90-98% |
| Wi-Fi 5 (AC), close to router, 5 GHz | 50-70% |
| Wi-Fi 6 (AX), close to router, 5 GHz | 70-90% |
| Wi-Fi 6E/7, close to router, 6 GHz | 80-95% |
| Wi-Fi through one wall, 5 GHz | 40-60% |
| Wi-Fi through two walls, 5 GHz | 20-40% |
| Wi-Fi on 2.4 GHz, any distance | 10-30% |
If your Wi-Fi test is within the expected band for your setup, the gap is normal physics. If it's below, you have a fixable problem.
Why Wi-Fi Is Slower Than Ethernet
1. Wi-Fi Is Half-Duplex
Ethernet sends and receives simultaneously on separate wire pairs (full-duplex). Wi-Fi uses one radio channel that cannot transmit and receive at the same time — devices take turns. A speed test on Wi-Fi sees roughly half the usable bandwidth compared to the same radio operating in a hypothetical full-duplex mode.
2. Shared Medium, Variable Speeds
Every device on your Wi-Fi network shares the same airtime. Each connects at a different modulation rate depending on signal strength. When a weak, slow device is transmitting, the whole network waits. An older phone or smart plug anchored to 2.4 GHz at 10 Mbps can drag down a Wi-Fi 6 laptop that could otherwise do 500 Mbps.
3. Interference
Every other Wi-Fi network, microwave, Bluetooth radio, and wireless camera in range adds noise. Interference forces retransmissions. Retransmissions eat into available bandwidth. Apartment buildings with 20+ visible networks can lose 50% of theoretical Wi-Fi throughput to contention alone.
4. Signal Attenuation
Walls, floors, and appliances absorb Wi-Fi signal. 5 GHz attenuates faster than 2.4 GHz, which is why 5 GHz is fast up close but drops off quickly. 6 GHz (Wi-Fi 6E/7) attenuates even faster — great in the same room, weak two rooms away.
5. Protocol Overhead
802.11 has more per-frame overhead than Ethernet: longer preambles, acknowledgement frames for every packet, and RTS/CTS negotiation when multiple devices compete. This overhead can consume 15-30% of raw physical-layer capacity.
6. Client Radio Limits
Your router may support Wi-Fi 6 at 2400 Mbps on paper, but your phone's radio might cap out at 1200 Mbps or 600 Mbps. Actual usable throughput is limited by the slower side of the link, and most single-stream consumer devices peak around 600-800 Mbps real-world.
Why Ethernet Is Almost Perfect
A wired connection between your device and router has a dedicated, full-duplex, uncontested channel. The main losses are tiny TCP/IP protocol overhead (3-5%) and router CPU if you are near gigabit speeds. Cat5e and Cat6 cables deliver a full 1 Gbps; Cat6a and Cat7 handle 10 Gbps if your hardware supports it.
Which Test Is "Real"?
Both are real. They answer different questions:
- Ethernet test: How much bandwidth is your ISP actually delivering?
- Wi-Fi test: How much of that bandwidth is reaching the specific device you care about?
Always start with an Ethernet test to baseline your ISP. If wired is close to plan speed, any gap on Wi-Fi is your local problem to solve. If wired is also slow, call your ISP.
How to Narrow the Wi-Fi Gap
- Connect to the 5 GHz or 6 GHz SSID (not 2.4 GHz)
- Stay within one or two rooms of the router for speed tests
- Upgrade to Wi-Fi 6 or Wi-Fi 7 if you still run Wi-Fi 5
- Move the router away from other electronics, metal, and aquariums
- Use mesh or a second AP if your home is larger than ~1500 sq ft
- Switch channels — use a Wi-Fi analyzer app to find an uncongested one
- Retire 2.4 GHz-only devices (or keep them on a separate SSID)
See improve Wi-Fi speed in an apartment and reduce Wi-Fi interference for specifics.
The Fair Way to Compare
If you want an apples-to-apples comparison:
- Run the test on Ethernet — this is your ceiling
- Run the same test on the same device over Wi-Fi in the same room as the router
- Run it again where you actually use Wi-Fi (couch, bedroom)
- The gap between each tells you where the loss is — router capacity, room-of-router Wi-Fi, or distance/walls
Frequently Asked Questions
Is Ethernet always faster than Wi-Fi?
Effectively yes. At the same speed tier, Ethernet consistently delivers 95-100% of plan speed while Wi-Fi delivers 40-90% depending on distance, walls, and standard. Wi-Fi 7 narrows but does not close the gap.
Why is my Wi-Fi half as fast as Ethernet?
Wi-Fi is half-duplex, shares airtime with all other devices on the network and in range, and loses bandwidth to interference and protocol overhead. Even a well-tuned Wi-Fi 6 network delivers roughly 70-90% of a wired connection in the same room.
Should I do my speed test over Wi-Fi or Ethernet?
Ethernet to validate your ISP; Wi-Fi to measure the specific device's experience. Run both. The Ethernet number tells you what you're paying for; the Wi-Fi number tells you what you're getting on the couch.