# Data Transfer Calculator

Calculate how long a file transfer takes at any speed. Supports Kbps to Gbps, accounts for protocol overhead. Works for downloads, uploads, and LAN transfers.

## What this calculates

Need to know how long a transfer will take? Enter your file size and connection speed to get an instant estimate. This calculator supports speeds from Kbps to Gbps, handles both bit-rate and byte-rate units, and accounts for protocol overhead that reduces real-world throughput.

## Inputs

- **File Size** — min 0.001
- **Size Unit** — options: Kilobytes (KB), Megabytes (MB), Gigabytes (GB), Terabytes (TB)
- **Transfer Speed** — min 0.1
- **Speed Unit** — options: Kilobits/sec (Kbps), Megabits/sec (Mbps), Gigabits/sec (Gbps), Kilobytes/sec (KB/s), Megabytes/sec (MB/s), Gigabytes/sec (GB/s)
- **Protocol Overhead** — options: None (raw speed), Low (5% - LAN transfer), Typical (10% - internet), High (20% - VPN/encrypted) — Network overhead reduces effective throughput

## Outputs

- **Transfer Time** — formatted as text
- **Total Seconds**
- **Effective Speed**
- **Total Data** — formatted as text — File size in bits for reference

## Details

Real-world transfer speeds are always lower than the advertised connection rate. Protocol overhead (TCP headers, encryption, error correction) typically eats 5-20% of the bandwidth, and network congestion can reduce it further.

Common transfer speed references:

  - Wi-Fi 5 (802.11ac): 200-800 Mbps real-world

  - Wi-Fi 6 (802.11ax): 500-1200 Mbps real-world

  - Gigabit Ethernet: 900-950 Mbps real-world

  - USB 3.0: 3-4 Gbps real-world

  - Thunderbolt 3: Up to 40 Gbps

  - NVMe SSD (internal): 3-7 GB/s

Remember: ISPs and hardware manufacturers advertise in bits (Mbps), while your operating system shows file sizes in bytes (MB). Divide the bit rate by 8 to get the byte rate.

## Frequently Asked Questions

**Q: Why is my transfer slower than calculated?**

A: Real-world speeds are affected by network congestion, server throttling, disk speed bottlenecks, Wi-Fi interference, and protocol overhead. The calculator accounts for overhead, but congestion and other factors are unpredictable. Expect 50-80% of your maximum connection speed in typical conditions.

**Q: What is the difference between Mbps and MB/s?**

A: Mbps (megabits per second) uses lowercase 'b' for bits. MB/s (megabytes per second) uses uppercase 'B' for bytes. Since 1 byte = 8 bits, divide Mbps by 8 to get MB/s. A 100 Mbps connection delivers about 12.5 MB/s.

**Q: What is protocol overhead?**

A: Protocol overhead is the extra data that networking protocols add to your transfer. TCP/IP headers, Ethernet framing, encryption (like TLS/VPN), and error correction all consume bandwidth without delivering useful file data. Typical overhead is 5-10% for plain transfers and 15-20% for VPN or encrypted connections.

**Q: Is it faster to transfer over USB or over the network?**

A: For local transfers, USB 3.0 (5 Gbps) is usually faster than Gigabit Ethernet (1 Gbps). USB 3.2 Gen 2 (10 Gbps) and Thunderbolt (40 Gbps) are even faster. For transfers between buildings or locations, network is the only option and speed depends on your internet connection.

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Source: https://vastcalc.com/calculators/everyday/data-transfer
Category: Everyday Life
Last updated: 2026-04-08