How long does it take to download 20GB at 100 Mbps?

About 27 minutes in ideal conditions. Real-world time can be longer due to overhead, Wi-Fi, and server limits.

Why is my download slower than my speed test?

Speed tests measure short bursts to nearby servers. Real downloads depend on the website/CDN, routing, congestion, and device limits.

Download Time Calculator – Mbps to GB Download Time (Instant Estimate)

Q: Is Mbps the same as MB/s?

No. 8 Mbps equals 1 MB/s. Providers advertise Mbps, while downloads often show MB/s.

Q: Does Wi-Fi reduce download speed?

Often yes. Wi‑Fi can be limited by distance and interference. Ethernet is usually faster and more stable.

How download speed works

Your internet plan is usually measured in Mbps (megabits per second). File sizes are usually shown in MB or GB (megabytes / gigabytes). Because there are 8 bits in a byte, MB/s ≈ Mbps ÷ 8. That simple conversion is the #1 reason people overestimate how fast downloads will finish.

Mbps vs MB/s (the quick conversion)

100 Mbps ≈ 12.5 MB/s
300 Mbps ≈ 37.5 MB/s
1 Gbps ≈ 125 MB/s

So if a file is 10 GB and your connection averages 12.5 MB/s, the download is roughly 10,240 MB ÷ 12.5 ≈ 819 seconds (about 13–14 minutes).

Why real downloads often take longer

Protocol overhead: TCP/IP, encryption, and error correction reduce usable throughput.
Wi‑Fi quality: distance, walls, and interference can cut speed dramatically.
Congestion: evening peak times can slow down shared networks.
Server limits: the website/CDN may throttle per-user download speed.
Disk / device limits: slow storage or CPU can bottleneck very fast connections.

This calculator gives a clean baseline estimate. If you want a “real world” guess, take your measured speed test result and subtract ~10–20%.

Download time examples

These examples assume a steady connection and ideal conditions. Your results can vary with Wi‑Fi quality, congestion, and server limits.

File size	50 Mbps	100 Mbps	500 Mbps
1 GB	~2 min 44 sec	~1 min 22 sec	~16 sec
5 GB	~13 min 39 sec	~6 min 50 sec	~1 min 22 sec
10 GB	~27 min 18 sec	~13 min 39 sec	~2 min 44 sec
50 GB	~2 hr 16 min	~1 hr 8 min	~13 min 39 sec

Frequently asked questions

Is Mbps the same as MB/s?

No. Mbps is megabits per second and MB/s is megabytes per second. 1 byte = 8 bits, so MB/s ≈ Mbps ÷ 8.

Why is my download speed slower than my internet plan?

Your plan is a maximum. Real speeds depend on Wi‑Fi signal, network congestion, server limits, and protocol overhead.

Does Wi‑Fi reduce download speed?

Often, yes. Wi‑Fi can be limited by distance, interference, router quality, and the Wi‑Fi standard. Ethernet is usually the fastest and most stable.

How long does it take to download a 10 GB file?

At 100 Mbps, a 10 GB download typically takes about 13–14 minutes in ideal conditions. Use the calculator above for your exact inputs.

What is a good download speed?

It depends on what you do. For basic browsing and HD streaming, 25–100 Mbps is often fine. For large game downloads, multiple devices, or 4K streaming, 100–500+ Mbps helps.

Why do speed tests and downloads show different numbers?

Speed tests measure throughput to specific servers under short bursts. Real downloads may be limited by the website/CDN, your device, or the route your traffic takes.

File size	—
Internet speed	—
Calculated seconds	—

File size	25 Mbps	50 Mbps	100 Mbps	250 Mbps	500 Mbps	1000 Mbps
1GB	~5m 28s	~2m 44s	~1m 22s	~33s	~16s	~8s
5GB	~27m 18s	~13m 39s	~6m 49s	~2m 44s	~1m 22s	~41s
10GB	~54m 36s	~27m 18s	~13m 39s	~5m 28s	~2m 44s	~1m 22s
20GB	~1h 49m	~54m 36s	~27m 18s	~10m 55s	~5m 28s	~2m 44s
50GB	~4h 33m	~2h 16m	~1h 8m	~27m 18s	~13m 39s	~6m 49s
100GB	~9h 6m	~4h 33m	~2h 16m	~54m 36s	~27m 18s	~13m 39s

Download Time Calculator (Mbps to GB & MB)