Bus Bandwidth Calculator

Work out bus bandwidth instantly with clear inputs, formula shown and shareable results.

About Bus Bandwidth Calculator

Bus bandwidth is clock times transfers per clock times bus width in bytes. Protocol efficiency accounts for address phases, arbitration, wait states and idle cycles — on a burst-oriented bus with long transfers it approaches 90%, on single-beat traffic it can fall below 40%.

Formula

Bus bandwidth

peak = clock x transfers per clock x width / 8; effective = peak x protocol efficiency

Worked example

With the default values below, Bus Bandwidth Calculator returns Effective bandwidth of 2,496.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Bus clock: 200 MHz
Bus width: 64 bits
Transfers per clock: 2 x
Protocol efficiency: 78 %

Results

Effective bandwidth: 2,496.00 MB/s
Peak bandwidth: 3,200.00 MB/s
Effective bandwidth: 19.97 Gbit/s
Bytes per transfer: 8.0 bytes

Step by step

1Values used
2Bus bandwidth
3Effective bandwidth= 2,496.00 MB/s
4Peak bandwidth= 3,200.00 MB/s
5Effective bandwidth= 19.97 Gbit/s
6Bytes per transfer= 8.0 bytes

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does burst length matter so much?

Address and handshake overhead is per transaction. Long bursts amortise it; single-beat accesses pay it every time.

What is double data rate?

Transferring on both clock edges, giving two transfers per clock. It doubles bandwidth without raising the clock frequency or its EMI penalty.