Network Tools Calculator

The CIDR Prefix is what determines Usable Hosts -- raising the CIDR Prefix shrinks the subnet and lowers Usable Hosts across the calculator's entire /0 to /32 range, because a larger prefix reserves more of the 32 address bits for the network portion and leaves fewer bits free for host addresses. The four IP Octets only select which network address the prefix is applied to; changing them alone does not change how many hosts that subnet can hold.

Because real subnets can only be sized in powers of two -- a /27 network always holds exactly 30 usable hosts, never 27 or 31. If a subnet needs 25 hosts, the planner must round up to the next power-of-two block that fits (here, a /27), and the difference between what was requested and what the block actually holds shows up as Waste. This is a structural property of binary subnetting, not a flaw in the calculation.

No -- it models a steady-state transfer at a constant fraction (Link Efficiency) of the rated Bandwidth, which is a reasonable planning estimate for sustained large transfers but does not simulate latency, TCP slow-start ramp-up, packet loss and retransmission, or congestion. Real transfers, especially short ones or those over congested or high-latency links, will typically take longer than this estimate suggests.

70-90% of the rated Bandwidth is typical for real network links, as noted in the Link Efficiency field's own help text, reflecting protocol overhead and the gap between a connection's advertised speed and its sustained real-world throughput. Older or more congested links can run below that range, while a clean, lightly loaded modern connection can sit near the top of it.

No -- the octets only identify which specific network address the calculator is analyzing (via the Network Address, Broadcast Address, and address-class outputs). Usable Hosts depends solely on the CIDR Prefix; entering different octet values while keeping the same CIDR Prefix always returns the same Usable Hosts figure, just anchored to a different network.