How to Run Check Disk (CHKDSK) on Windows

If your computer is running slowly, files are acting strangely, or Windows is throwing up errors about your storage drive, Check Disk — the built-in Windows utility known as CHKDSK — is one of the first diagnostic tools worth reaching for. It scans your drive for file system errors, bad sectors, and other storage-level problems that can quietly cause bigger issues over time.

Here's exactly how to run it, what your options mean, and what affects the results you'll get.

What Check Disk Actually Does

CHKDSK (pronounced "check disk") is a Windows command-line tool that examines the integrity of a storage drive. It works on both HDDs (hard disk drives) and SSDs (solid-state drives), though what it finds and fixes differs depending on the drive type.

It performs two core functions:

• Scanning for file system errors — checks that the logical structure of your files and folders (the index Windows uses to find data) is intact
• Scanning for bad sectors — identifies physical or logical areas of the drive that can no longer reliably store data

On an HDD, bad sectors are often physical damage. On an SSD, they're more commonly logical errors or worn-out memory cells. CHKDSK can mark bad sectors so Windows stops writing data to them.

How to Run Check Disk: Three Methods

Method 1: Command Prompt (Most Control) 💻

This is the most flexible approach and gives you access to all CHKDSK parameters.

1. Press Windows + S, type cmd, right-click Command Prompt, and select Run as administrator
2. Type the following and press Enter:

chkdsk C: /f /r 

What the flags mean:

If you're scanning your active system drive (usually C:), Windows can't lock it while the OS is running. It will ask to schedule the scan on the next restart — type Y and reboot.

For a secondary drive (like D:), the scan runs immediately.

Method 2: File Explorer (No Command Line Needed)

1. Open File Explorer and go to This PC
2. Right-click the drive you want to check and select Properties
3. Click the Tools tab
4. Under Error checking, click Check
5. Click Scan drive when prompted

This method runs a basic scan. If errors are found, you'll be offered the option to repair them. It's the most accessible route for users who prefer a graphical interface.

Method 3: Windows Recovery Environment (For Serious Problems)

If Windows won't boot properly, you can run CHKDSK from outside the operating system:

1. Boot from a Windows installation USB or use Advanced Startup Options (hold Shift while clicking Restart)
2. Navigate to Troubleshoot → Advanced Options → Command Prompt
3. Identify your drive letter (it may not be C: in the recovery environment — type diskpart then list volume to check)
4. Run chkdsk C: /f /r with the correct letter

This method is particularly useful when the system drive has errors severe enough to prevent normal startup.

Factors That Affect How Long It Takes — and What It Finds

Drive size is the biggest time variable. Scanning a nearly full 4TB HDD with the /r flag can take several hours. An SSD of the same size scans significantly faster due to how solid-state storage handles read operations.

Drive health matters too. A drive with many bad sectors or heavy fragmentation takes longer to process. If CHKDSK is taking unusually long, that itself can be a signal the drive is struggling.

OS version affects available options. The /scan flag, which allows online scanning without dismounting the drive, is only available on Windows 8 and later. On Windows 7, scanning the system drive always requires a restart.

File system type also plays a role. CHKDSK works on NTFS, FAT32, and exFAT volumes, but its repair capabilities are most robust on NTFS — the default format for modern Windows system drives.

Reading the Results

After the scan completes, CHKDSK displays a summary. Key things to look for:

• "Windows has scanned the file system and found no problems" — the drive is logically healthy
• "Errors found and corrected" — CHKDSK repaired file system issues; monitor the drive going forward
• Bad sectors reported — this is a warning sign, especially on HDDs. A few isolated bad sectors may be stable, but a growing count suggests the drive is deteriorating 🔴

You can also view CHKDSK results after the fact by opening Event Viewer (search for it in the Start menu), navigating to Windows Logs → Application, and filtering for source Wininit or Chkdsk.

When CHKDSK Isn't Enough

CHKDSK addresses file system-level and sector-level problems, but it doesn't replace a full drive health diagnostic. If you're seeing signs of serious drive failure — repeated errors, the drive disappearing from Windows, clicking sounds from an HDD — tools like S.M.A.R.T. monitoring utilities provide a deeper picture of hardware health.

CHKDSK also won't recover already-lost data. If files have been corrupted or deleted, that's a job for dedicated data recovery software, which operates differently from a disk integrity scan.

How useful CHKDSK is for your situation ultimately depends on the type of drive you have, what symptoms you're experiencing, and whether the issue is at the file system level or something deeper — which varies considerably from one machine to the next.