File Transfer Time Calculator

Estimated Transfer Time

Finishes by {{ finish_time_local }}

{{ file_size_value }} {{ file_size_unit }} {{ bandwidth_value }} {{ bandwidth_unit }} {{ overhead_percent }} % OH RTT {{ rtt_ms }} ms Win {{ tcp_window_mb }} MB {{ connections }}× conn -{{ compression_percent }} % size

Limited by: {{ limiting_factor }}

File size:

Size standard:

Bandwidth:

Overhead (%):

{{ overhead_percent }} %

Compression (%):

{{ compression_percent }} %

Latency (RTT):

TCP window:

Connections:

flows

Bandwidth share (%):

{{ bandwidth_share_percent }} %

Packet loss:

MSS:

bytes

Mathis C:

Handshake RTTs:

RTT

Protocol preset:

Metric	Value	Copy
Total bytes	{{ format(total_bytes) }}
Effective bytes	{{ format(effective_bytes) }}
Raw rate (B/s)	{{ format(raw_bps) }}
After share (B/s)	{{ format(available_raw_bps) }}
Post-overhead (B/s)	{{ format(post_overhead_bps) }}
BDP cap (B/s)	{{ bdp_limit_bps ? format(bdp_limit_bps) : '—' }}
Loss cap (B/s)	{{ loss_limit_bps ? format(loss_limit_bps) : '—' }}
Effective (B/s)	{{ format(eff_bps) }}
Handshake time (s)	{{ format(handshake_time_seconds) }}
Time (s)	{{ format(transfer_time_seconds) }}
Finish (local)	{{ finish_time_local }}

Categories: Calculator , Networking

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File transfer time is the elapsed period required to move a payload across a network link, reflecting both the usable throughput and any startup delay. Many plans depend on a realistic estimate so backups, migrations, and large syncs finish when expected, and an estimate file transfer time for large files helps you choose when to run them.

Inputs are the payload size and the link rate in units people actually use, and results report a total duration alongside a friendly breakdown. Real links rarely deliver headline speed, so the estimate accounts for protocol overhead, available share on a busy line, optional compression, and common limiting effects such as latency and packet loss.

The workflow is simple. Pick a size standard that matches your environment, set size and bandwidth, then apply advanced details only when they matter. The output reads as a compact duration and a local finish time so scheduling is straightforward.

For a quick sense check, a 700 megabyte payload over a 10 megabyte per second link completes in about 73.40 seconds, which feels like a minute and a bit. Treat the number as a planning guide since real traffic can fluctuate.

Technical Details:

The estimate focuses on payload bytes and the effective rate that the connection sustains over the transfer window. Size may be interpreted with binary prefixes or decimal prefixes; both families are supported to keep comparisons honest across tools and storage systems.

The computation builds an effective throughput from the advertised link rate by applying your bandwidth share and protocol overhead, then considers two caps that often matter on wide‑area paths: the bandwidth–delay product limit from finite receive windows and the loss‑based limit captured by a standard throughput model. The smallest applicable rate governs the result.

Results include total seconds and a compact readable form, plus the startup cost from connection handshakes when requested. Values near boundaries or with large compression percentages should be read with care because small changes can swing the limiting factor.

Comparisons are most meaningful when you keep size standard, units, and advanced settings consistent. Estimates describe a single transfer flow or multiple parallel flows as configured and do not model congestion control ramps or variable traffic outside your share.

\begin{matrix} S {total}_{B} & = & size \times multiplier \\ S {eff}_{B} & = & S {total}_{B} \cdot (1 - c) \\ R {raw}_{B / s} & = & bandwidth converted to bytes per second \\ R {share}_{B / s} & = & R {raw}_{B / s} \cdot s \\ R {post}_{B / s} & = & R {share}_{B / s} \cdot (1 - o) \\ R {BDP}_{B / s} & = & \frac{W B_{bytes}}{RTT s_{\sec}} \cdot n \\ R {loss}_{B / s} & = & \frac{MSS \cdot C}{RTT s_{\sec} \cdot \sqrt{p}} \\ R {eff}_{B / s} & = & \min (R {post}_{B / s}, R {BDP}_{B / s}, R {loss}_{B / s}) \\ T {hs}_{s} & = & RTT s_{\sec} \cdot r \\ T {total}_{s} & = & T {hs}_{s} + \frac{S {eff}_{B}}{R {eff}_{B / s}} \end{matrix}

Symbols and units
Symbol	Meaning	Unit/Datatype	Source
`S_total`	Total payload bytes	B	Derived
`S_eff`	Bytes after compression	B	Derived
`R_raw`	Advertised throughput converted	B/s	Derived
`s`	Share of link	fraction	Input
`o`	Protocol overhead	fraction	Input
`R_post`	Throughput after share and overhead	B/s	Derived
`W`	Per‑connection receive window	MB	Input
`n`	Parallel connections	count	Input
`RTT_s`	Round‑trip time	s	Input
`MSS`	Maximum segment size	B	Input
`C`	Throughput constant	unitless	Input
`p`	Packet loss rate	fraction	Input
`R_BDP`	BDP‑based cap	B/s	Derived
`R_loss`	Loss‑based cap	B/s	Derived
`R_eff`	Effective throughput	B/s	Derived
`T_hs`	Handshake time	s	Derived
`T_total`	Transfer time	s	Derived

Worked example. Size 700 MB with the binary standard (1 MB = 1,048,576 B); bandwidth 10 MB/s; share 100%; overhead 0%; no caps from latency or loss.

\begin{matrix} S {total}_{B} & = & 700 \times 1, 048, 576 = 734, 003, 200 \\ R {eff}_{B / s} & = & 10 \times 10^{6} = 10, 000, 000 \\ T {total}_{s} & = & \frac{734003200}{10000000} = 73.40032 \approx 73.40 \end{matrix}

Interpretation: about 1 minute 13 seconds, with no startup delay.

Limiting factor meanings
Limiting Factor	Interpretation	Action Cue
Post‑overhead	The adjusted link rate dominates.	Increase share or reduce overhead.
BDP cap	Window size and latency restrict throughput.	Grow receive window or add parallel flows.
Loss cap	Packet loss and latency bound the rate.	Lower loss or shorten path round‑trip time.

Units, precision, and rounding

Binary standard: 1 KB = 1,024; decimal standard: 1 KB = 1,000. KiB/MiB/GiB are always binary.
Bandwidth accepts bits per second and bytes per second; bits are converted by dividing by 8.
Total time is rounded to two decimals; the readable form shows whole seconds with days, hours, and minutes.

Validation and bounds

Input validation and bounds
Field	Type	Min	Max	Step/Pattern
File size	number	0	—	—
File size unit	enum	—	—	B, KB, MB, GB, TB, KiB, MiB, GiB, TiB
Size standard	enum	—	—	IEC or SI
Bandwidth	number	0	—	—
Bandwidth unit	enum	—	—	bps, Kbps, Mbps, Gbps, KB/s, MB/s, GB/s
Overhead	range	0	50	step 1 %
Compression	range	0	90	step 1 %
Bandwidth share	range	1	100	step 1 %
Latency (RTT)	number	0	—	ms
TCP window	number	0	—	MB, step 0.1
Connections	number	1	—	integer
Packet loss	number	0	—	% step 0.001
MSS	number	200	—	bytes
Mathis C	number	0.1	—	step 0.01
Handshake RTTs	number	0	—	integer
Protocol preset	enum	—	—	Custom, TCP+TLS, SFTP/SSH, SMB, NFS

I/O formats

Inputs and outputs
Input	Accepted Families	Output	Encoding/Precision
Payload size	Binary or decimal units	Total and effective bytes	Integer bytes
Bandwidth	Bits or bytes per second	Rates pre‑ and post‑overhead	Two decimals
Advanced parameters	Overhead, share, latency, window, loss, MSS, constant, handshakes	Effective throughput, caps, time, finish time	Time to 0.01 s

Networking & storage behavior

All calculations run locally in the browser UI layer; no external requests are made for the estimate.
The charting layer is optional and does not affect the numeric result.

Performance & complexity

Computation is constant‑time for metrics and linear in a small fixed grid for the timeline.
Rendering cost scales with the number of displayed points.

Diagnostics & determinism

Identical inputs produce identical outputs.
Displayed numbers format to two decimals for consistency.

Security considerations

Inputs are numeric and enumerated; no untrusted text is interpreted.
Clipboard actions, when used, require user gesture and browser permission.

Assumptions & limitations

BDP cap applies only when latency and window are both positive.
Loss cap applies only when both latency and loss are positive.
Window units are decimal megabytes (1 MB = 1,000,000 B).
Size standard changes only the multiplier, not the numeric entry.
Compression applies before transfer and reduces payload bytes.
Handshake cost is a fixed number of round trips.
Parallel connections multiply the BDP cap linearly.
Heads‑up The loss model is simplified and omits ramp‑up dynamics.

Edge cases & error sources

Zero bandwidth or zero effective bytes yields no result.
Very large numbers can exceed integer precision in external tools.
Loss entered as a percent must be non‑negative.
Non‑integer connections are rounded by input constraints.
Latency of zero disables handshake and the two caps.
Overhead or share near extremes can dominate the estimate.
MSS below the minimum is clamped by input.
Locale formatting may affect grouping separators when copied.
Timeline sampling is approximate and uses a fixed grid.
System sleep or tab throttling does not affect computed numbers.

Privacy & compliance

No data is transmitted or stored server‑side; results are computed in the browser.

Step‑by‑Step Guide:

Estimate file transfer time and identify the limiting factor with these steps.

Choose the size standard that matches your tools.
Enter File size and select its unit.
Enter Bandwidth and select its unit.
Expand Advanced to set overhead, share, and optional compression.
Add latency, window, and connections if the path is not local.
Set packet loss, MSS, and the throughput constant when needed.
Optionally pick a protocol preset, then fine‑tune values.

Example: 20 GiB at 500 Mbps with 5% overhead and 50 ms latency returns both the effective rate and the finish time.

Use the result to schedule windows and to compare scenarios quickly.

FAQ:

Is my data stored?

No. Inputs drive a local calculation, and nothing is sent to a server.

Clipboard use requires your action.

How accurate is the estimate?

It is a planning number. Real paths vary with traffic, congestion control, and loss. Keep inputs consistent to compare runs.

Which units should I use?

Pick the size standard your tools show. Binary uses powers of 1024; decimal uses powers of 1000.

Can I use it offline?

Yes, once loaded. The calculation itself does not require connectivity.

Does it cost anything?

No purchase is required to read or use the estimator.

How do I choose IEC vs SI?

Match the labels you see elsewhere. Storage tools often use binary prefixes, while link rates are commonly decimal.

What does “Limited by: BDP cap” mean?

Latency and window size restrict the rate. Increase the window or add more connections to raise the cap.

Where does the startup time come from?

It is a fixed count of round trips you specify, multiplied by the round‑trip time.

Troubleshooting:

No result shows: ensure size and bandwidth are both positive.
Time seems too long: check the size standard matches your files.
Loss cap dominates: confirm loss units are in percent.
BDP cap dominates: raise the window or reduce latency.
Chart missing: the charting layer may not be available; the estimate still works.
Copy fails: grant clipboard permission and retry after a user action.

A zero or missing effective rate makes time undefined. Verify bandwidth units and that share is not zero.

Advanced Tips:

Tip Keep scenarios comparable by fixing the size standard across runs.

Tip Use compression only for types that shrink; media files rarely benefit.

Tip Add a small handshake cost for protocols that negotiate before transfer.

Tip When latency is high, parallel flows can help saturate the path.

Tip Set the loss constant and MSS explicitly if you measure them on your path.

Tip Use the limiting‑factor label to decide whether to tune overhead, window, or path quality first.

Glossary:

Throughput: Amount of data transferred per second.
Protocol overhead: Headers and control information that reduce payload rate.
Round‑trip time (RTT): Elapsed time for a signal to go out and return.
BDP: Bandwidth–delay product; in‑flight data capacity.
MSS: Maximum payload size of a single segment.
Handshake: Setup exchanges needed before payload transfer.