Bandwidth Calculator

What it does

This tool answers two very common IT questions:

1. "How long will this transfer take?" — given a file size and a connection speed (bandwidth), it calculates the estimated transfer time.
2. "How much data can I move in X time?" — given a bandwidth and a duration, it calculates how much data can be transferred.

It also includes a unit converter between bit-based bandwidth units (bps, Kbps, Mbps, Gbps) and byte-based data size units (KB, MB, GB, TB), since the distinction between "bits" and "bytes" (and the factor of 8 between them) is a frequent source of confusion and support tickets.

Try it

Unit converter

How it works

• Bits vs. Bytes: network bandwidth is almost always advertised in bits per second (e.g. "100 Mbps"), while file sizes are almost always shown in bytes (e.g. "500 MB"). This tool converts everything to a common base unit (bits per second and bytes) internally using the standard factor: 1 byte = 8 bits.
• Decimal units: this calculator uses the decimal (SI) convention — 1 KB = 1,000 bytes, 1 MB = 1,000,000 bytes, 1 Kbps = 1,000 bps, etc. — which matches how ISPs advertise speeds and how most transfer-time estimates are commonly communicated. It intentionally does not use the binary (1024-based) KiB/MiB convention.
• Transfer time = data size (in bits) ÷ bandwidth (in bits per second).
• Data transferred = bandwidth (in bits per second) × time (in seconds), converted back to bytes.
• Required bandwidth = data size (in bits) ÷ time (in seconds).
• Real-world transfers are almost always slower than the theoretical number due to protocol overhead (TCP/IP headers, retransmissions), other traffic sharing the link, and the fact that "Mbps" sold by an ISP is a maximum, not a guarantee. Treat results here as a best-case estimate.

Common reference speeds