About the Bandwidth Calculator
Bandwidth planning goes wrong in two predictable places: unit confusion and averaging. Network capacity is quoted in bits per second while file sizes are in bytes, a factor of eight that turns a comfortable link into a saturated one. And sizing to the average ignores that traffic is bursty, so a link provisioned for the mean is congested for a meaningful fraction of every day.
This calculator works in both directions — total throughput from a per-unit rate and a count, or the transfer time for a given volume over a given link — and keeps the bit and byte units explicit so the factor of eight never has to be held in your head.
Treat the output as a floor rather than a forecast. Protocol overhead, retransmissions, and the gap between peak and mean all consume real capacity, so a link sized exactly to the computed requirement will be undersized in practice.
Frequently asked questions
What is the difference between Mbps and MBps?
Lowercase b is bits, uppercase B is bytes, and there are eight bits in a byte. A 100 Mbps link moves at most about 12.5 MB per second. Network equipment and internet plans are quoted in bits per second; file sizes and download managers work in bytes. Almost every order-of-magnitude bandwidth mistake is this one.
Why is my actual transfer slower than the calculation?
The calculation gives the theoretical wire rate. Real throughput loses several percent to protocol headers, and considerably more to anything that stalls the sender. On a long-distance link the usual limiter is not bandwidth at all but the TCP window relative to round-trip time — a single connection across a high-latency path can leave most of a fast link idle no matter how much capacity you buy.
Should I size a link to average or peak traffic?
Neither, exactly. Sizing to the average guarantees congestion during every busy period; sizing to the absolute peak wastes money on capacity used for minutes a month. The common practice is to size to a high percentile of observed traffic — the 95th percentile is what many transit providers bill on — and then add headroom for growth.
How do I convert between Mbps and GB per month?
Multiply the rate in megabits per second by the number of seconds in the period, then divide by eight for bytes. A sustained 1 Mbps for a 30-day month is roughly 324 GB. The trap is that sustained rates are rare — real traffic follows a daily cycle, so a link that peaks at 1 Mbps transfers far less than that figure.
Does the calculation account for overhead?
No, it gives the raw figure. Ethernet, IP, and TCP headers together cost a few percent on large packets and much more on small ones, since the header is a fixed cost per packet regardless of payload. Workloads dominated by small packets — telemetry, chatty RPC — can lose a surprising share of nominal capacity to framing alone.