Network Throughput Calculator
Network throughput is the real-world data transfer rate achievable on a network link, always lower than the advertised bandwidth due to protocol overhead, utilization limits, and packet loss. Network engineers, capacity planners, and system architects use throughput calculations to size WAN circuits, estimate file transfer times, plan backup windows, and validate that a link can support the required traffic volume. This calculator takes your link speed in Mbps, protocol overhead percentage, target utilization, and packet loss rate to compute effective throughput in Mbps, MB per second, and GB per hour. It also calculates the time required to transfer a file of a given size.
Throughput formula
eff_Mbps = link_Mbps * (1 - overhead/100) * (utilization/100) * (1 - loss/100)
eff_MBs = eff_Mbps / 8
eff_GBhr = eff_MBs * 3600 / 1024
transfer_sec = file_GB * 1024 / eff_MBs
Throughput optimization tips
- Use jumbo frames (9,000-byte MTU) on LAN and storage networks to reduce header overhead from 2.7% to 0.04%.
- Enable TCP window scaling and increase receive buffer sizes for high-latency long-distance links (TCP tuning).
- Monitor packet loss carefully: even 0.1% loss reduces TCP throughput significantly on high-speed links.
- For bulk transfers, consider UDP-based protocols (e.g., QUIC, RDMA) that avoid TCP's congestion-control penalties.
- Use link aggregation (LACP) to combine multiple physical links for higher aggregate throughput and redundancy.
Frequently asked questions
What is network throughput?
Network throughput is the actual rate at which useful data is transferred across a network link, measured in bits per second (bps) or multiples thereof. It is always less than the raw link speed (bandwidth) because of protocol overhead, packet headers, retransmissions, and the fact that no link runs at 100% utilization continuously.
What is the difference between bandwidth and throughput?
Bandwidth is the maximum theoretical data rate of a network link (e.g., 1 Gbps Ethernet). Throughput is the actual measured data transfer rate after accounting for overhead and utilization. Effective throughput on a 1 Gbps link typically ranges from 600-940 Mbps depending on protocol and traffic patterns.
How much overhead does TCP add?
TCP adds 20 bytes of header per packet over the IP header. With a standard 1,500-byte MTU and a 40-byte TCP/IP header (20 bytes IP + 20 bytes TCP), the protocol overhead is roughly 2.7%. TLS encryption adds another 5-20 bytes per record. Total overhead including Ethernet framing is typically 5-8%.
How do I calculate file transfer time?
Transfer time = file_size_GB / throughput_GBps. For a 10 GB file over a 100 Mbps effective throughput link: 10 GB / (0.1 Gbps / 8) = 10 / 0.0125 = 800 seconds, or about 13 minutes. Always use effective throughput (not link speed) for accurate time estimates.
What factors reduce network throughput below link speed?
Key factors include: protocol overhead (headers, ACKs), link utilization (links rarely run at 100%), packet loss (causing TCP retransmissions), network congestion and queuing delays, CPU limitations on the sending or receiving host, and physical layer issues such as cable quality and signal interference.
Official sources
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.