How to Use Stopwatch in C# for Measuring Time

Use the Stopwatch class from System.Diagnostics to measure elapsed time in C#. Start it with Start(), stop with Stop(), and get the elapsed time using Elapsed or ElapsedMilliseconds properties.

Syntax

The Stopwatch class provides methods and properties to measure time intervals. Key parts include:

• Start(): Begins timing.
• Stop(): Stops timing.
• Reset(): Clears the elapsed time.
• Elapsed: Gets the total elapsed time as a TimeSpan.
• ElapsedMilliseconds: Gets the elapsed time in milliseconds as a long.

csharp

using System.Diagnostics;

Stopwatch stopwatch = new Stopwatch();
stopwatch.Start();
// Code to time
stopwatch.Stop();
TimeSpan elapsed = stopwatch.Elapsed;
long milliseconds = stopwatch.ElapsedMilliseconds;

Example

This example shows how to measure the time taken to pause the program for 2 seconds using Thread.Sleep. It starts the stopwatch, waits, stops it, and prints the elapsed time.

csharp

using System;
using System.Diagnostics;
using System.Threading;

class Program
{
    static void Main()
    {
        Stopwatch stopwatch = new Stopwatch();
        stopwatch.Start();

        Thread.Sleep(2000); // Pause for 2 seconds

        stopwatch.Stop();

        Console.WriteLine($"Elapsed time: {stopwatch.ElapsedMilliseconds} ms");
    }
}

Output

Elapsed time: 2000 ms

Common Pitfalls

Common mistakes when using Stopwatch include:

• Not calling Start() before measuring time.
• Calling Start() multiple times without Reset(), which continues timing instead of restarting.
• Using ElapsedMilliseconds for very short intervals where ElapsedTicks might be more precise.

Always stop the stopwatch before reading elapsed time to get accurate results.

csharp

using System.Diagnostics;

Stopwatch sw = new Stopwatch();
// Wrong: reading elapsed before starting
Console.WriteLine(sw.ElapsedMilliseconds); // Outputs 0

sw.Start();
// Do work
sw.Stop();
Console.WriteLine(sw.ElapsedMilliseconds); // Correct usage

// To restart timing
sw.Reset();
sw.Start();

Output

0
[Elapsed time after Stop() call]

Quick Reference

Method/Property	Description
Start()	Starts or resumes measuring elapsed time.
Stop()	Stops measuring elapsed time.
Reset()	Stops time and resets elapsed time to zero.
Restart()	Resets and starts measuring elapsed time.
Elapsed	Gets the elapsed time as a TimeSpan.
ElapsedMilliseconds	Gets the elapsed time in milliseconds.
ElapsedTicks	Gets the elapsed time in timer ticks (high precision).

Key Takeaways

Use Stopwatch.Start() and Stopwatch.Stop() to measure elapsed time accurately.

Read elapsed time only after stopping the stopwatch for correct results.

Reset the stopwatch before reusing it to avoid accumulating time.

ElapsedMilliseconds gives time in ms; use Elapsed for TimeSpan details.

Stopwatch is ideal for performance timing and measuring code execution duration.