This tool computes the **rise time** of a signal from its **bandwidth**.

**Formula**

**T _{rise} = 0.35 / BW **

where

**T**is the Rise Time in Nanoseconds (_{rise}**ns**)**BW**is the Bandwidth in Gigahertz (**GHz**)

**Background**

As the bandwidth of the signal increases the rise time of the signal decreases. The rise time is defined as the 10-90% rise time of a square wave.

**Calculation Example**

**What is the rise time of a 50 MHz sine wave?**

The calculator is used to find **T _{rise} = 0.35 / 0.05 = 7 nanoseconds**.

**What is the rise time of a 50 MHz square wave?**

The bandwidth of a 50 MHz square wave for practical applications is calculated as 5×50 = 250 MHz. **T _{rise} = 0.35 / 0.25 = 1.4 nanoseconds**.

In theory a square wave has an infinite number of harmonics. The amplitude of harmonics decreases as the frequency increases. For practical purposes, considering the first five harmonics is adequate.

**Related Calculators**

**References**

[1] Bandwidth of a signal from its rise time: Rule of Thumb #1. In this post the author derives the relationship between rise time and bandwidth empirically.

[2] How do I determine what bandwidth of scope I require for my application? An application note that estimates a 2% measurement error when the five times rule is used.