What affects internet speed?
Latency, bandwidth, overheads, and why real-world speeds vary.
The basics: speed vs quality
Quick definition
Internet “speed” combines bandwidth (how much data you can move) and latency (how fast each request starts). The stable feeling of apps also depends on jitter (variability) and packet loss.
Streaming and large downloads care most about bandwidth. Games, calls, and browsing feel snappy when latency and jitter are low. Packet loss hurts both by triggering retransmissions.
Bandwidth vs latency (and jitter)
What to know
- Bandwidth is the theoretical maximum data rate (e.g., 100 Mbps).
- Throughput is what you actually get after overheads and congestion.
- Latency (ms) and jitter define how responsive interactive apps feel.
Even with high bandwidth, high latency can make pages and apps feel sluggish because each request waits longer before any bytes arrive.
Learn more: Ping & jitter explained →
Throughput and protocol overheads
Real tests rarely hit the plan rate. Headers (TCP/UDP, TLS, HTTP), MTU limits, and retransmissions reduce the share of useful payload. A 100 Mbps plan often measures around 85–95 Mbps even on ideal Ethernet.
- Each packet carries headers that don’t count toward your file or video data
- Small MTU or fragmentation increases overhead
- Packet loss forces retries, shaving throughput
Wi‑Fi vs Ethernet
Ethernet is consistent and low‑latency. Wi‑Fi varies with distance, walls, interference (neighbor routers, microwaves), and band. 2.4 GHz travels farther but is slower and busier; 5/6 GHz is faster but shorter range.
See also: Improve your Wi‑Fi speed →
Distance, peering, and congestion
The farther your traffic travels and the more networks it crosses, the higher the latency and the greater the risk of bottlenecks. During busy hours, shared links and upstream peers can saturate.
Tip: pick speed‑test servers closer to you, test at different times, and try wired vs Wi‑Fi.
Real‑world examples
A 100 Mbps plan may test at ~90 Mbps on Wi‑Fi due to overheads and signal quality. The same line often reaches 95 Mbps+ on Ethernet under similar conditions.
Key takeaways
Remember:
- Bandwidth sets the ceiling; latency and jitter shape how fast it feels
- Throughput is always below the plan due to protocol overheads
- Wi‑Fi quality swings with placement, interference, and band choice
- Distance and peering add delay; local servers feel faster