Why is my real download slower than advertised?

Three usual reasons: Mbps vs MB/s (divide the advertised number by 8), ~5–15% protocol overhead (the calculator's overhead option models this), and the server or Wi-Fi being the bottleneck rather than your plan.

Why does uploading take so much longer than downloading?

Most cable and DSL plans are asymmetric — a '500 Mbps' plan might upload at only 20 Mbps. Enter your actual upload speed from a speed test, not the plan's headline number.

Download & Upload Time Calculator

How long a file takes to download or upload at any connection speed — with the Mbps vs MB/s confusion sorted out for you.

File Size

Download Speed

Include ~10% protocol overhead (real-world estimate)

Downloading 20 GB at 100 Mbps takes about

29m 38s

100 Mbps ≈ 12.5 MB/s — ISPs advertise megaBITS (Mbps); files are measured in megaBYTES (8 bits each).

This File at Common Speeds

Connection	Time
5 Mbps	9h 52m 36s
10 Mbps	4h 56m 18s
25 Mbps	1h 58m 31s
50 Mbps	59m 16s
100 Mbps	29m 38s
300 Mbps	9m 53s
500 Mbps	5m 56s
1 Gbps (fiber)	2m 58s
2 Gbps	1m 29s
5 Gbps	36s
8 Gbps	22s
10 Gbps (10G fiber)	18s

Loading Tool…

What Is the Download & Upload Time Calculator?

The Download & Upload Time Calculator tells you how long a file transfer will take: pick a file size, enter your connection speed, and get the time — plus a table showing the same file at common speeds from 5 Mbps DSL to gigabit fiber. It handles the classic confusion built into internet plans: ISPs sell megaBITS per second (Mbps) while files are measured in megaBYTES (MB, 8 bits each), so a '100 Mbps' plan moves at most 12.5 MB per second. Speed can be entered in Kbps, Mbps, Gbps or MB/s, and an optional real-world overhead setting knocks ~10% off for protocol overhead so the estimate matches what actually happens. Presets cover common files — photos, songs, HD and 4K movies, modern games, even an hour of ProRes footage.

How It Works

Choose Download or Upload, set the file size and your connection speed (run a speed test if you're not sure — upload is usually much slower than download), and read the time. The table below shows how the same file fares on other connections.

When to Use It

Use it before queuing a big game download, to estimate how long client footage takes to upload, to sanity-check whether your plan can handle cloud backups, or to explain to someone why 100 Mbps doesn't mean 100 MB per second.

Frequently Asked Questions

Why is my real download slower than advertised?: Three usual reasons: Mbps vs MB/s (divide the advertised number by 8), ~5–15% protocol overhead (the calculator's overhead option models this), and the server or Wi-Fi being the bottleneck rather than your plan.
Why does uploading take so much longer than downloading?: Most cable and DSL plans are asymmetric — a '500 Mbps' plan might upload at only 20 Mbps. Enter your actual upload speed from a speed test, not the plan's headline number.

Found an issue? Send Feedback. See our data sources and update policy for tools that depend on changing information.