Network Bandwidth Calculator
Calculate file transfer time, required bandwidth, or actual throughput based on file size, link speed, and protocol overhead.
TCP/IP overhead is typically 3–10%. Set 0 for raw throughput.
Realistic sustained utilisation of the link (typically 60–90%).
Formulas Used
Transfer Time:
Transfer Time = File Size (bytes) ÷ Effective Throughput (B/s)
Effective Throughput = Link Speed × Link Utilisation × (1 − Overhead Fraction)
Required Bandwidth:
Required Raw Speed = File Size ÷ (Transfer Time × Utilisation × (1 − Overhead))
Actual Throughput:
Effective Throughput = Link Speed × Utilisation × (1 − Overhead)
Overall Efficiency (%) = Effective Throughput ÷ Raw Link Speed × 100
Unit Conversions:
1 byte = 8 bits | 1 KB = 1,024 B | 1 MB = 1,048,576 B |
1 Mbps = 1,000,000 bits/s (SI) | 1 MB/s = 8 Mbps
Assumptions & References
- Bandwidth units follow SI (1 Mbps = 10⁶ bits/s) while storage units follow binary (1 MB = 2²⁰ bytes), consistent with industry practice.
- Protocol overhead of 3–10% accounts for TCP/IP headers, ACKs, retransmissions, and framing (RFC 793, RFC 791).
- Link utilisation of 60–80% is a common engineering rule of thumb for sustained traffic; 100% utilisation causes queuing and congestion.
- The model assumes a single-hop, error-free link. Real-world latency, RTT, and TCP window size can further limit throughput (Bandwidth-Delay Product).
- For WAN links, TCP throughput is bounded by: Throughput ≤ TCP Window Size / RTT (Mathis et al., 1997).
- Reference: Tanenbaum & Wetherall, Computer Networks, 5th ed.; Forouzan, Data Communications and Networking, 5th ed.