Download Time Calculator

About this calculator

Download time is the file size in bits divided by the connection speed in bits per second. A 100 MB file over a 100 kbps link takes 8,000 seconds — 2 hours 13 minutes 20 seconds. If that "100 kb/s" is really 100 kilobytes per second, the same file takes 1,000 seconds, or 16 minutes 40 seconds: the factor of eight between bits and bytes is the whole difference, and it is why your ISP quotes megabits while your file manager shows megabytes. This calculator also handles the decimal-vs-binary prefix distinction (MB = 1,000,000 bytes; MiB = 1,048,576 bytes). Enter your file size and bandwidth, pick the right units, and get the result in hours, minutes and seconds.

How to read your results

The result shows the theoretical download time broken into hours, minutes and seconds. Real-world transfers are slower — TCP/IP protocol overhead, connection congestion, Wi-Fi packet loss and server throttling all eat into the rated speed. A 5–15% reduction from the theoretical figure is normal on a good connection; expect more on mobile or public Wi-Fi. The optional overhead field lets you model this directly.

How it's calculated

Download time in seconds equals (file size in bytes × 8) ÷ bandwidth in bits per second. The factor of 8 converts bytes to bits, matching the unit your ISP uses for connection speed. For decimal size units (KB, MB, GB, TB) the calculator applies SI prefixes: 1 MB = 10⁶ bytes, 1 GB = 10⁹ bytes. For binary size units (KiB, MiB, GiB, TiB) the calculator applies IEC 80000-13 prefixes: 1 MiB = 2²⁰ = 1,048,576 bytes, 1 GiB = 2³⁰ bytes. Bandwidth units are normalised similarly: 1 Mbps = 10⁶ bits per second; 1 MBps = 8 × 10⁶ bits per second. If an overhead percentage p is supplied, the raw time is divided by (1 − p/100) to model the share of capacity consumed by protocol headers and retransmissions. The final result is expressed in hours, minutes and whole seconds.

Worked example

File size: 700 MB (a DVD-quality video, decimal megabytes). Connection: 50 Mbps (megabits per second).

The calculator converts 700 MB to 5,600,000,000 bits (700 × 1,000,000 × 8), divides by 50,000,000 bps, and returns 112 seconds — 1 minute 52 seconds. Note: at the same 50 Mbps, a 700 MiB file (binary) would take about 117 seconds because MiB is roughly 4.86% larger than MB.

Frequently asked questions

How long does it take to download a 100 MB file at 100 kb/s?

It depends on whether "kb/s" means kilobits or kilobytes, and the difference is a factor of eight. At 100 kilobits per second, 100 MB is 800,000,000 bits ÷ 100,000 bits per second = 8,000 seconds, or 2 hours 13 minutes 20 seconds. At 100 kilobytes per second the same file takes 1,000 seconds — 16 minutes 40 seconds. If the file is 100 MiB rather than 100 MB it is about 4.86% larger, so at 100 kilobits per second it takes roughly 8,389 seconds. ISPs quote bits; file managers show bytes.

Why is my actual download slower than the calculator predicts?

The calculator gives the theoretical ceiling — bits of payload divided by bits of capacity. Real transfers include TCP acknowledgement packets, TLS handshakes, HTTP headers, and retransmissions, so effective throughput is usually 80–95% of the rated speed. Distance to the server, Wi-Fi interference and ISP throttling add further delays. Use the overhead field (try 10%) to get a more realistic estimate.

What is the difference between Mbps and MBps?

Mbps is megabits per second; MBps is megabytes per second. One byte equals 8 bits, so 50 Mbps is only 6.25 MBps. Internet service providers advertise in megabits; operating systems and download managers usually show transfer rates in megabytes. Mixing these units up is the single most common reason people think their connection is slower than advertised.

When should I use MB vs MiB for my file size?

Use MB (megabytes, 10⁶ = 1,000,000 bytes) for files reported by macOS, streaming services, storage manufacturers and most web content. Use MiB (mebibytes, 2²⁰ = 1,048,576 bytes) if your tool shows "MiB" or counts in binary units — Windows Explorer does (its "MB" label actually means mebibytes), as do Linux and some disk utilities. If in doubt, check whether the tool appending the label spells it with a lower-case "i".

Does the overhead percentage account for my Wi-Fi or VPN?

It is a simple scaling factor rather than a protocol-specific model. A 10% overhead means the calculator assumes only 90% of your rated bandwidth carries useful payload, which roughly captures typical Wi-Fi or VPN cost. If you are on a heavily loaded network or a high-latency satellite connection, 15–30% may be more realistic.

Can I use this for upload time as well?

Yes — enter your upload bandwidth in the connection speed field. The physics is identical: upload time equals file size in bits divided by upload speed in bits per second. Most home connections have asymmetric speeds (upload is 5–20× slower than download), so uploading a large file takes considerably longer than downloading it.

Sources

• Definitions of the SI units: The binary prefixes — National Institute of Standards and Technology
• SI prefixes — Bureau International des Poids et Mesures

Reviewed by the YouCalc Team · Last reviewed June 12, 2026