Bandwidth and transfer-time calculator

Estimate how long a backup, restore or file transfer could take. Choose the data units, stated bandwidth and an efficiency assumption. Free, without an account.

Plan a transfer

Inputs stay in memory on this page. No file uploads, speed tests or network probes. Download creates a local text file.

Data size

Data size unit (bytes)

Size is in bytes (uppercase B); 1 byte = 8 bits. GB and GiB are different. Maximum: 1,000 TB decimal.

Bandwidth

Bandwidth unit (bits per second)

Mbps means megabits per second, not MB/s (megabytes per second). Convert MB/s to Mbps by multiplying by 8. Maximum: 1,000,000 Gbps.

Efficiency (%)

More than 0%, up to 100%. Your assumption for the usable share of stated bandwidth; 80% is an example, not a measured or recommended value.

Use positive numbers with a decimal point, up to 9 decimal places. No units, commas or exponents in number fields.

Worked example: 1 GB decimal, 100 Mbps, 80% efficiency.

Ideal duration

1 min 20 s

80 seconds at full stated bandwidth.

Adjusted duration

1 min 40 s

100 seconds at 80% efficiency.

Effective throughput: 80,000,000 bits/second. Data size: 1,000,000,000 bytes.

These are rounded estimates, not a completion-time guarantee. Latency, throttling, disk speed, protocol behavior and service limits are not measured. The adjusted duration is limited to 1 trillion seconds.

Formulas and units

Ideal seconds = data size in bytes × 8 / bandwidth in bits per second.

Adjusted seconds = ideal seconds / (efficiency / 100).

Decimal units use powers of 1,000: 1 GB = 1,000,000,000 bytes. Binary units use powers of 1,024: 1 GiB = 1,073,741,824 bytes. Bandwidth units here are decimal bits per second. At 100 Mbps, the ideal byte rate is 12.5 MB/s.

Durations are elapsed time: a minute is 60 seconds, an hour 3,600 seconds and a day 86,400 seconds. No calendar date, timezone or daylight-saving conversion is involved.

Worked examples and planning limits

For 1 GB over 100 Mbps: 1,000,000,000 × 8 / 100,000,000 = 80 seconds ideally. At 80% efficiency: 80 / 0.8 = 100 seconds adjusted.

For 1 GiB at the same bandwidth: the ideal duration is 85.89934592 seconds; at 80% efficiency it is 107.3741824 seconds. For 100 GB over 1 Gbps, the ideal duration is 800 seconds, or 13 minutes 20 seconds.

Use the slowest relevant link and a realistic throughput assumption for your own setup. Parallel transfers share capacity; compression can change the bytes sent. A backup may also spend time scanning, compressing, verifying and writing data. This estimator models one constant-rate transfer only.

Open free local connections in ObserveifyNow to organize direct infrastructure reads. Protected Proxmox VE, Proxmox Backup Server and Beszel reads require the native app; the browser supports published Uptime Kuma status pages. This calculator does not measure transfer speed.