Free Bandwidth Requirement calculator with clear step-by-step results.
Sizes an internet or WAN circuit from concurrent user count and per-user bitrate. Offered load is grossed up for protocol overhead and retransmissions, then divided by a target utilisation ceiling - running a link above roughly 70% pushes queueing delay and jitter up sharply even though throughput still fits.
Offered load
Offered Mbps = users x kbps per user x (1 + overhead) / 1000
Provisioned capacity
Circuit = offered load / target utilisation
Roughly 100 kbps for browsing, 1.5 Mbps for 720p video, 3-5 Mbps for 1080p and 25 Mbps for 4K. Voice calls need only 100 kbps but are far more sensitive to jitter.
Packet networks queue. As utilisation approaches capacity, latency and loss rise non-linearly, so interactive traffic degrades long before the link is technically full.