# PCIe Bandwidth Calculator

This tool computes the PCI express bandwidth (or throughput) and time for a file transfer.

## Calculator

In the calculator below

• Select the PCI version number
• Enter number of lanes or link width (x1 to x16)
• Enter the amount of data to be transferred

The tool provides the PCIe bandwidth and the time it takes to transfer data. In this post we have also explained the fundamentals of PCIe bandwidth.

## What is PCIe Bandwidth?

The bandwidth of PCIe refers to the speed at which data can be transferred per second across the PCIe bus.

The PCIe link is consists of dedicated unidirectional couples of serial (1-bit), point-to-point connections known as lanes. Bandwidth is then determined by the number of lanes (1-16) and the generation of the PCIe standard (currently up to 7).

## Example Calculations

### How are the transfer rate numbers derived?

For PCIe 3.0, a single lane transmits symbols at every edge of a 4 GHz clock. This results in a transmission rate of 8 GT/s (use the MHz to MT/s calculator)

The protocol encodes 128 bits of data with 130 bits (128b/130b encoding) to provide enough state changes to allow reasonable clock recovery and alignment of the data stream at the receiver.

Therefore the raw transfer rate of a PCI lane is

8 GT/s * 128/130 * (1/8) = 0.985 GB/s = 985 MB/s

This number is multiplied by the number of available lanes (x16 in the calculator above) to get the full link transfer rate. The overhead due to error correction should be accounted for as well.

### PCIe 5.0

The theoretical bandwidth of PCIe 5.0 with 16 lanes is 63 GBps. With 1 Gbps for error correction protocols and the PCIe headers overhead, the number drops to 62.9 GBps.

## Background

PCIe, short for Peripheral Component Interconnect Express, is a high-speed serial computer expansion bus standard used to connect various components inside a computer system. It serves as an interface between the motherboard and peripherals such as graphics cards, sound cards, network cards, and storage devices.

### What is a PCIe slot?

A PCIe slot is a physical connection point on the motherboard for inserting PCIe cards or expansion devices. The number of lanes determines the available bandwidth and determines the capabilities of the slot.

A PCIe x4 slot for example can accommodate PCIe cards or devices that require up to four lanes for data transfer. This slot provides a higher bandwidth compared to smaller x2 or x1 slots.

### How to measure PCIe bandwidth?

The tool on this page can be used to estimate the throughput. It depends on the version number, lanes. Practically we also have to subtract the overhead of 1 Gb/s for error correction.