This download time calculator estimates how long a file will take to transfer at a given speed — the honest version, with the bits-vs-bytes factor of 8 that makes “100 megabit” internet move “12.5 megabyte” files per second.
Bits, Bytes and the Factor of 8
Internet speeds are sold in bits per second; files are measured in bytes — 8 bits each. So a 100 Mbps connection moves at most 12.5 MB/s, and time = (file size in bytes × 8) ÷ speed in bits/s. The GB/GiB distinction (1 GiB = 1.074 GB) shifts results by up to 7% at scale — both units are offered above, and our Data Storage Converter untangles the whole family. Part of our Other Calculators collection.
Worked Examples (Verified)
- 10 GB at 100 Mbps: 80 gigabits ÷ 100 Mbps = 800 s = 13 min 20 s ideal; at the default 90% efficiency ≈ 14 min 49 s — the widget’s numbers
- A 100 GB game at 25 Mbps rural broadband: 800 Gb ÷ 25 = 32,000 s ≈ 8.9 hours — an overnight download, which is why pre-loading exists
- The same game at 1 Gbps fiber: 800 s ≈ 13 minutes — and usually then capped by the console’s storage write speed or the store’s servers (real-world efficiency is not pessimism, it’s experience)
- Uploads are the trap: a 2 GB video on a cable plan’s 10 Mbps upload = 27 minutes — enter upload speed for sending, which on asymmetric plans is a tenth of the headline figure
Why Reality Runs Slower Than the Poster
- TCP/IP and encryption overhead: ~3–10% before anything else goes wrong.
- Single-connection limits: many servers throttle per connection; download managers open parallel streams for a reason.
- Wi-Fi: a “1 Gbps” plan through two walls on 2.4 GHz may see 40–80 Mbps at the desk — measure at the device (speed test) and enter that.
- Peak hours: shared neighborhood capacity can halve evening throughput on cable networks.
Related Tools
- Data Storage Converter — GB, GiB, TB and bits, all converted
- Text to Binary Converter — bytes, down at the bit level
- Other Calculators — the full collection
Frequently Asked Questions
How do I calculate download time?
Convert the file to bits (size × 8, watching GB vs GiB), divide by speed in bits per second. 10 GB = 80 Gb; at 100 Mbps that’s 800 seconds ≈ 13 minutes ideal — then allow ~10% for real-world overhead.
Why is my 100 Mbps internet only downloading at 12 MB/s?
It isn’t slow — that’s exact: 100 megabits ÷ 8 = 12.5 megabytes per second maximum. Browsers and stores display MB/s while ISPs advertise Mbps; the factor of 8 reconciles the two numbers.
What’s the difference between GB and GiB here?
GB = 10⁹ bytes (drive/ISP marketing, file systems on some OSes); GiB = 2³⁰ = 1.074 × 10⁹ bytes (Windows’ reported sizes). A “100 GB” download measured by Windows is really ~93 GiB — the 7% discrepancy appears in transfer estimates too, so this calculator offers both units.
How long does a 50 GB game take on 200 Mbps?
400 Gb ÷ 200 Mbps = 2,000 s ≈ 33 minutes ideal, call it 37–40 in practice. On gigabit: ~7 minutes ideal. These are the two numbers that sell fiber upgrades.
Does streaming count differently?
Streaming consumes the same arithmetic live: 4K video streams at ~15–25 Mbps continuously (about 7–11 GB per hour) — a capped connection’s budget drains in exactly the hours this calculator computes.
Is this download time calculator free?
Yes — free, instant, no sign-up.