Download Time Calculator
How long will a download or upload take? File size × speed with a real-world efficiency factor — answer in h/min/s, common-speed table and reverse mode.
Your file at common speeds
| Connection | Theoretical | At 90% |
|---|
Need it done by a deadline?
Same file, fixed time budget. The answer is the sustained speed your connection must actually hold — plus the advertised plan that implies at your efficiency setting.
It already ran — what speed did you get?
Enter how long the transfer actually took and get your achieved throughput, in Mbps and in the MB/s your download manager showed.
The one thing everyone gets wrong
Your plan is advertised in megabits, your downloads are measured in megabytes, and one byte is eight bits. That’s the whole trick: 100 Mbps is 12.5 MB/s on paper and about 11 MB/s in practice — the line under the speed input always shows both numbers so the units never get lost. If you take one thing from this page: divide Mbps by 8 to get the MB/s your browser will report, then knock off ~10% for protocol overhead.
The efficiency factor exists because no real transfer runs at the line rate. TCP/IP and TLS headers, retransmissions and Wi-Fi airtime all take a cut — 90% is a fair default for a healthy wired connection, 60–75% is honest for busy Wi-Fi, and clearing the field gives you the theoretical 100% floor. The common-speeds table shows both columns side by side so the gap is always visible.
Honest about the units
File sizes have the same split personality as speeds: drive makers and networks count in decimal gigabytes (1 GB = 1,000 MB), while your OS often displays binary gibibytes (1 GiB = 1,024 MiB) mislabeled as GB. The unit system switch above does the conversion properly — flip it and the answer shifts by about 7% at the GB level, which is exactly why a “50 GB” game and a “50 GiB” backup don’t finish together.
What the calculator assumes
A steady connection at the speed you enter, for the whole transfer — it doesn’t model slow starts, server-side caps, or the last mile of a download stalling at 99%. Real downloads drift, so treat the answer as the honest middle of a range, not a promise. The reverse panels exist for exactly this reason: time a real transfer once and you’ll know your true throughput instead of trusting the brochure.
For the deeper dives: Mbps vs MB/s — bits vs bytes explained untangles the units once and for all, why real speed is lower than advertised lists every tax on your bandwidth, download time math with worked examples shows the formula on real files, and data-cap math for streaming and games turns speeds into monthly gigabyte budgets.
Mbps vs MB/s — Bits vs Bytes, Explained Once
Your plan is megabits, your downloads are megabytes — here's the 8:1 rule that explains the "missing" speed.
Open →Why Your Download Speed Is Lower Than Advertised
Every tax on your bandwidth, in order — from the 8:1 unit trick to Wi-Fi airtime and rate-limited servers.
Open →Download Time Math, With Worked Examples
One formula does it all — six worked examples show the unit traps and the honest efficiency correction.
Open →How Much Data Do Streaming and Games Actually Use?
GB per hour for Netflix, 4K, cloud gaming and calls — and the monthly formula that tells you if your cap survives.
Open →Frequently asked questions
How do I calculate download time?
Convert the file size to bits and divide by your speed in bits per second: time = (size × 8) ÷ speed. One gigabyte is 8 gigabits, so a 1 GB file on a 100 Mbps line takes 80 seconds in theory — about 89 seconds at the 90% real-world efficiency this calculator applies by default.
Why does my 100 Mbps connection only download at 12 MB/s?
Because nothing is wrong — those are the same speed in different units. Internet plans are sold in megabits per second while browsers and download managers show megabytes per second, and 1 byte = 8 bits. 100 Mbps ÷ 8 = 12.5 MB/s theoretical, roughly 11 MB/s after normal protocol overhead. The full explanation is in Mbps vs MB/s.
Is 1 GB equal to 1,000 or 1,024 MB?
Both, depending on the convention. Storage makers and network gear use decimal units (1 GB = 1,000 MB); operating systems often display binary units (1 GiB = 1,024 MiB) while still labelling them GB. The Unit system switch lets you pick — binary sizes are ~7% larger at the GB level, which is why a '1 GB' file can take noticeably longer than expected.
What is the real-world efficiency factor?
No transfer gets 100% of the line rate: TCP/IP headers, TLS, retransmissions and Wi-Fi losses eat a slice. A wired connection on a healthy network typically lands at 85–95%, which is why the default is 90%. Drop it to 60–75% for congested Wi-Fi, or clear the field for the theoretical 100% ceiling.
Does this work for uploads too?
Yes — the math is identical, just enter your upload speed. Watch out for asymmetric plans: a cable connection advertised as 500 Mbps often uploads at only 10–35 Mbps, so a cloud backup takes far longer than the download of the same data.
How do I find my real speed?
Run a speed test on a wired connection, or measure directly: download a file of known size, time it, and use the second reverse panel below — 'size ÷ time' is your achieved throughput. If your speed test shows 300 Mbps but downloads crawl at 30, the bottleneck is the server or Wi-Fi, not your plan — see why real speed is lower than advertised.
How long does a 50 GB game take to download?
50 GB is 400 gigabits. On 100 Mbps at 90% efficiency that's about 74 minutes; on 500 Mbps about 15 minutes; on 25 Mbps about 5 hours. The table under the calculator shows your exact file at five common speeds — and the worked examples walk the math.
Latest articles
Mbps vs MB/s — Bits vs Bytes, Explained Once
Your plan is megabits, your downloads are megabytes — here's the 8:1 rule that explains the "missing" speed.
How Much Data Do Streaming and Games Actually Use?
GB per hour for Netflix, 4K, cloud gaming and calls — and the monthly formula that tells you if your cap survives.
Download Time Math, With Worked Examples
One formula does it all — six worked examples show the unit traps and the honest efficiency correction.
Why Your Download Speed Is Lower Than Advertised
Every tax on your bandwidth, in order — from the 8:1 unit trick to Wi-Fi airtime and rate-limited servers.