Memory Bandwidth Calculator

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

About Memory Bandwidth Calculator

Peak bandwidth is transfers per second times bus width in bytes times channels. Real bandwidth is 70-90% of that because of refresh, bank conflicts, read/write turnaround and command overhead — the efficiency term is where memory controller quality shows.

Formula

Memory bandwidth

BW = data rate x (width / 8) x channels; effective = peak x bus efficiency

Worked example

With the default values below, Memory Bandwidth Calculator returns Effective bandwidth of 87.04. Change any input above and every figure here is recalculated in your browser.

Inputs used

Data rate per pin: 6,400 MT/s
Bus width: 64 bits
Channels: 2 channels
Bus efficiency: 85 %

Results

Effective bandwidth: 87.04 GB/s
Peak bandwidth: 102.40 GB/s
Bandwidth per channel: 51.20 GB/s
Bytes per transfer: 8 bytes

Step by step

1Values used
2Memory bandwidth
3Effective bandwidth= 87.04 GB/s
4Peak bandwidth= 102.40 GB/s
5Bandwidth per channel= 51.20 GB/s
6Bytes per transfer= 8 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 is efficiency below 100%?

Refresh, activate and precharge commands, read-to-write bus turnaround and row conflicts all consume bus cycles that carry no data.

How is bandwidth increased?

More channels, higher data rate, or wider buses. HBM takes the wide-and-slow route with 1024-bit stacks, saving power per bit.