# Data Transfer Time Calculator

> Work out how long it takes to transfer data of any size (kB to TB, KiB to TiB) over a link in kbps, Mbps, Gbps or MB/s, with an efficiency allowance.

Category: IT, networking & security · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/data-transfer-time-calculator

Transfer time = data in bits ÷ effective speed in bits per second. Sizes are in bytes and line speeds in bits, so multiply the size by 8 first.

Also called: Download time calculator, Upload time calculator, File transfer calculator.

## Inputs
- Data size (default 10)
- Size unit (options: bytes, kB (1,000 bytes), MB (10⁶ bytes), GB (10⁹ bytes), TB (10¹² bytes), KiB (1,024 bytes), MiB (2²⁰ bytes), GiB (2³⁰ bytes), TiB (2⁴⁰ bytes); default GB)
- Connection speed (default 100)
- Speed unit (options: kbps (kilobits/s), Mbps (megabits/s), Gbps (gigabits/s), MB/s (megabytes/s), MiB/s (mebibytes/s); default Mbps)
- Efficiency (unit %; default 90)

## Results
- Transfer time
- In seconds
- In minutes
- In hours
- Effective speed

## Formula

```
Time (s) = Size in bytes × 8 ÷ (Speed in bits per second × Efficiency%)
```

Where:
- 8: bits per byte
- Speed: kbps = 10³, Mbps = 10⁶, Gbps = 10⁹ bits per second; MB/s = 8 × 10⁶ bits per second

## Worked example
1. Size: 10 GB = 10 × 10⁹ bytes × 8 = 80 × 10⁹ bits.
2. Effective speed: 100 Mbps × 90% = 90 × 10⁶ bits/s.
3. Time: 80 × 10⁹ ÷ 90 × 10⁶ = 888.9 s ≈ 14 min 49 s.

**Result:** A 10 GB file takes about 14 minutes 49 seconds on a 100 Mbps line at 90% efficiency (13 min 20 s at the full line rate).

## What the result means

If a transfer of many terabytes takes days, shipping a physical disk or a provider’s offline transfer appliance may be faster. For backups, compare the result with your backup window.

## Assumptions and limits
- The speed is sustained for the whole transfer.
- Very high-latency links can be limited by TCP window size rather than line rate; small files add per-file overhead.

## Questions

### What is the difference between Mbps and MB/s?

Mbps is megabits per second; MB/s is megabytes per second. 1 MB/s = 8 Mbps, so a 100 Mbps line delivers at most 12.5 MB/s.

### Why does my 1 TB drive show as 931 GB?

The drive maker uses decimal TB (10¹² bytes); many operating systems show binary GiB (2³⁰ bytes) labelled “GB”. 10¹² ÷ 2³⁰ ≈ 931.

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Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/data-transfer-time-calculator