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Transfer Time Calculator

Calculate how long a migration, backup or file transfer will take.

Transfer tips

  • Internet speeds are usually in bits, not bytes (divide by 8 to get MB/s)
  • Consider protocol overhead (~10% for TCP/IP)
  • Upload speeds are usually lower than download speeds
  • For large transfers, consider compressing first

Factors affecting actual transfer speed

The time shown by our calculator is a theoretical estimate. In practice, multiple factors can reduce actual transfer speed. Understanding them will help you better plan your migrations and backups.

Disk speed: Mechanical hard drives (HDD) have sequential read speeds of ~150-200 MB/s, while modern SSDs reach 500-3500 MB/s. If your disk is slower than your network connection, the disk becomes the bottleneck.

Concurrency and file count: Transferring a single large file is more efficient than thousands of small files. Each small file requires its own TCP negotiation, headers, and acknowledgments.

Encryption and compression: Encrypted transfers (SCP, SFTP, HTTPS, VPN) add CPU overhead. On servers with slow CPUs, encryption can limit speed to under 100 Mbps even on a 1 Gbps link.

Frequently Asked Questions

How to calculate file transfer time?
Transfer time is calculated by dividing file size by transfer speed: Time = Size / Speed. For example, a 10 GB (10,000 MB) file over a 100 Mbps (12.5 MB/s) connection: 10,000 / 12.5 = 800 seconds ≈ 13.3 minutes. Our calculator does this automatically and supports any unit.

What is the difference between Mbps and MB/s?
Mbps (megabits per second) measures speed in bits, while MB/s (megabytes per second) measures in bytes. 1 byte = 8 bits, so 100 Mbps = 12.5 MB/s. ISPs advertise speeds in Mbps because the number looks larger. For real transfer calculations, always convert to MB/s first by dividing by 8.

How does TCP overhead affect actual transfer time?
TCP/IP overhead reduces useful speed by 5-15% due to packet headers, acknowledgments (ACKs), and retransmissions. For practical calculations, subtract ~10% from nominal speed. For example, on a 1 Gbps link, realistic throughput is ~900 Mbps. On connections with high latency or packet loss, overhead can be significantly higher.

How to calculate server migration time?
To calculate migration time: 1) Sum the total data to transfer (databases, files, configs). 2) Identify your source upload speed and destination download speed (the lower is the bottleneck). 3) Apply Time = Size / Speed (in bytes/s). 4) Multiply by 1.15 for TCP overhead. 5) Add time for incremental sync if applicable.

How long does 1 TB take to transfer at different speeds?
At 100 Mbps (~11.4 MB/s real): 1 TB ≈ 24.4 hours. At 500 Mbps (~57 MB/s): ≈ 4.9 hours. At 1 Gbps (~114 MB/s): ≈ 2.4 hours. At 10 Gbps (~1.14 GB/s): ≈ 14.6 minutes. These calculations assume constant speed without disk limitations, which in practice can add significant time.

Why is my actual transfer slower than my connection speed?
Several factors: 1) Upload speed is usually lower than download (asymmetric connections). 2) Disk speed can be the bottleneck. 3) TCP/IP overhead reduces useful speed. 4) Latency (RTT) especially affects high-ping connections. 5) Network congestion during peak hours. 6) CPU limitations on devices with encryption (VPN, HTTPS).
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