Why Windows takes so long to calculate the size of a folder and how to speed it up

¿Why does Windows take so long to calculate the size of a folder? If you've ever stared at the Windows window while the "Calculating..." message appears when opening a large folder, you're not alone. Many users wonder why Windows takes so long to calculate the size of a folderespecially when the equipment is relatively new or very powerful and everything else is running smoothly.

In reality, behind that simple “Calculating size…” there is a rather complex process influenced by the disk, the CPU, the file system, the way the Explorer is configured and even third-party programs such as the antivirus. Understanding what's happening and how to optimize it can make the difference between working smoothly or getting frustrated every time you open a folder with many files..

Why does Windows take so long to calculate the size of a folder?

 

The first thing is to understand exactly what Windows does when you open a folder or ask it to calculate its size. The system has to go through all the files and subfolders, read their metadata, and add up their sizes one by one.If the folder contains thousands of items, many subfolders, or files widely scattered across the disk, this process inevitably becomes slower.

Unlike files, whose size is stored directly and is very fast to read, Folders do not store their full size "by default" in the NTFS file systemEvery time Windows wants to display this information, it has to recalculate it. Doing this continuously for all folders in real time would consume a lot of resources, so Explorer only calculates it on demand (properties, progress bars, certain views, etc.).

Additionally, if the folder is on a mechanical hard drive (HDD), The difference in physical access time to the disk is very noticeable.The read/write head has to jump around reading small fragments, which adds latency. Even on very fast SSDs or M.2 drives, if there are hundreds of thousands of files or many small files, the number of input/output operations (IOPS) skyrockets, and that also slows down the calculation.

As if that weren't enough, Windows may be creating thumbnails, reading metadata such as tags, dimensions, or multimedia information, and cross-referencing all of this with the search index.Each of those steps adds extra work to the CPU, the disk, and File Explorer itself.

Other factors that make Explorer slow

Beyond calculating folder size, there are a number of factors that can cause Explorer to take a long time to open or list content. It's usually not a single culprit, but rather the sum of several small problems that eventually cause everything to run in fits and starts..

One of the most frequent reasons is the lack of available memory. If you have many applications open at the same time and the RAM is almost full, Windows starts using the paging file on disk.which is much slower. In that context, opening a folder with many items can take forever, because the system is constantly swapping data between RAM and disk.

Background applications also have an influence. Third-party programs that integrate with Explorer (cloud services, compressors, editors, antivirus, etc.) can hook into every folder opening. to analyze files, generate previews, or add entries to the context menu. If any of them "gets stuck," it drags the entire Explorer down with them.

On devices where the problem appears suddenly after an update, It is relatively common for a Windows patch to introduce changes that affect Explorer's performance.Microsoft usually fixes this with later updates, but in the meantime the system may be slower than normal when opening folders or searching for files.

Finally, we must not forget the hardware itself. A hard drive with damaged sectors, an aging external drive, or a CPU at its temperature limit can cause Explorer to respond with exasperating slowness.even if the rest of the system appears "normal" at first glance.

Getting started: Basic Windows maintenance

Before we get into advanced settings, it's a good idea to leave the system in a reasonable state. If the disk is full of junk, fragmented (on HDDs), with corrupted files, or with many unnecessary applications running in the background, any attempt to optimize Explorer will fall short..

The first thing is to free up space. Windows 10 and Windows 11 include the "Disk Cleanup" tool, which allows you to delete temporary files, update remnants, thumbnails, the recycle bin, etc.You can access it by right-clicking on the drive (usually C:), choosing "Properties," and then "Disk Cleanup." It's common to recover several gigabytes if it's never been used.

With some free space, defragmenting mechanical hard drives makes sense. Defragmentation reorganizes files so that they are physically closer together on the diskThis reduces the time it takes the read/write head to read them. Windows itself offers the "Defragment and Optimize Drives" tool, which you can find in the Start menu and schedule to run periodically.

It is also recommended to install all pending updates. From Settings > Update & Security > Windows Update you can check for new updatesThey often include performance improvements and bug fixes that affect the Explorer or the services it uses.

Finally, if you notice that the system is generally slow, you can follow Microsoft's recommendations to improve performance: Clean up startup programs, uninstall unused software, adjust visual effects, and check the status of system files with the built-in toolsLeaving the computer "light" makes a big difference when opening large folders.

Restart Windows Explorer and close any hanging processes

Sometimes the problem is not so much the size of the folder as the Explorer itself, which has become stuck after hours of use, window switching and continuous openings. Restarting the explorer.exe process is usually one of the quickest ways to bring it back to life. without needing to restart the entire computer.

To do this, open Task Manager (Ctrl + Shift + Esc), go to the “Processes” tab and look for “Windows Explorer”. Right-click on it and choose "Restart" to close it and restart it cleanly.This also restarts many processes associated with the interface.

It can happen that, even if you close the Explorer windows, orphaned processes remain in the background, continuing to consume resourcesIn the Task Manager itself, with Explorer closed, check if there are any instances of explorer.exe or related processes and manually end them by right-clicking > “End task”.

In some cases, a simple restart of the computer using the "Restart" option (not just "Shut down" and then turn on) may be sufficient. The restart forces the complete closure of processes and services that might be affecting the Explorer's performance.Whereas a poorly utilized shutdown in systems with fast startup can keep certain states cached.

Control background applications

If Explorer takes a long time to open only when you have many things running (browser with dozens of tabs, games, editors, virtual machines, etc.), it is very likely that the bottleneck is in the RAM or the CPU. The more applications you have open, the harder it is for Windows to manage memory, caches, and disk access..

A good practice is to close anything you're not really using. From the Task Manager you can see which programs are consuming the most CPU, memory or disk, and close those that are running unnecessarily.This frees up resources so that Explorer can read and display folder contents more smoothly.

If you suspect that a specific program is interfering with Explorer, you can perform a "clean boot" of the system. A clean boot starts Windows with only essential services and drivers, temporarily disabling third-party software running in the background.It's a useful way to check if the problem is caused by external applications.

To do this, the system configuration tool (msconfig) and the task manager are used to disable startup items. If the Explorer runs much better when you boot in clean mode, it's a clear indication that some added program is sabotaging performance..

History, thumbnails, and folder options

Explorer stores a lot of information about what you do: recent folders, open files, frequent locations, custom views… All that history and cache, if it accumulates for a long time, can end up slowing down the application.especially if some internal files become corrupted.

From within the Explorer itself, in the “View” tab you can access “Options”. In the “Privacy” section, you have a button to clear the File Explorer history.This removes the recent access list and can help make openings somewhat faster.

Thumbnails are another classic. When you enter a folder with many photos, videos, or documents with previews, Windows generates and saves thumbnails so they can be quickly displayed next time.If the thumbnail cache becomes corrupted or grows too large, performance will suffer.

To regenerate that cache, you can again use the "Disk Cleanup" tool on the system drive and check the "Thumbnails" box. Deleting thumbnails will cause Windows to rebuild them from scratch when you reopen folders with media content.This often corrects problems with slowness or freezing when loading previews.

Another useful option is to reset the folder options. If you've heavily customized the views, icons, layouts, and filters, a specific setting might be hindering the Explorer's performance.From Folder Options > “View” tab, you can use the “Reset Folders” button to return to the default settings.

Folder optimization and indexing service

Windows offers a folder optimization feature that, when used correctly, can improve performance, but when applied incorrectly, can do the exact opposite. Each folder can be optimized for a specific type of content: general items, documents, images, music, videos, etc.

If you have a folder with thousands of mixed files (for example, TV series, photos, subtitles, documents), and it's optimized for "Images" or "Music", The Explorer will attempt to read extra metadata from each file to provide specific columns (artist, album, dimensions, duration…)All of this translates into longer waiting times when opening and calculating the content.

The solution is simple: right-click on the problematic folder, choose "Properties" and go to the "Customize" tab. In “Optimize this folder for…”, select “General elements” and, if you want, check the box to apply that template to subfolders as well.This reduces the workload when listing items.

For its part, the Windows search and indexing service creates an index to speed up searches, but if it breaks down or gets stuck, This can cause the Explorer search bar and the loading of certain directories to be very slow.From the Control Panel you can open “Indexing Options” and use the built-in troubleshooting tool to detect and correct errors.

In that wizard you can select, for example, that "Searching or indexing is slow" and follow the steps to have Windows repair the index. If the problem was the search service, you'll notice an improvement both when searching and when listing some folders that depend on that index..

Conflicting updates, SFC, and disk check

It is not uncommon for some computers to start experiencing performance problems in Explorer or when working with files after a major update. If you notice that the problem appeared right after installing a specific update, it's worth checking if uninstalling it helps..

In Windows 10 and Windows 11 you can go to Settings > Windows Update > “Update history” and then to “Uninstall updates”. Find the most recent one (by date), note its code, and try uninstalling it.Then, restart your computer and check if the Explorer behaves normally again.

Another key element is the integrity of system files. Windows includes the SFC (System File Checker) tool, which is used to locate and repair corrupted system files. If there are errors in core components, the Explorer may become unstable or very slow..

To run it, open Command Prompt as administrator and type the command sfc /scannow. The process will take a few minutes and, when finished, it will tell you if there were corrupted files and if they have been repaired correctly.A subsequent restart is recommended to apply all changes.

Finally, it's important to check the physical and logical status of the disk. Windows offers the Check Disk (chkdsk) tool to scan drives for errors. If the disk has bad sectors or problems with its file system, accessing folders can be extremely slow..

From a CMD window with administrator privileges, run the command chkdsk /f on the drive you want to check (for example, chkdsk C: /f). The system may ask you to restart to complete the scan, especially if it's the system drive.Once the errors are corrected, read performance usually improves significantly.

Network folders, external drives and energy saving

If the folder that takes a long time to open is on a NAS, a USB hard drive, or a drive shared through the router, the problem may not be with your PC at all. Network drives and many external hard drives enter sleep modes to save energy when they have been unused for a while..

When you try to access a folder on a drive that is "asleep", the device has to wake up, spin up the disks (if it is an HDD) and reconnect to the network properly. This process can take several seconds during which Windows seems to "think" without doing anything., displaying the calculation message or leaving the window blank.

On NAS servers and some external drives, you can adjust power saving policies from their control panel, increasing the time before going into sleep mode or disabling that function. If you constantly work with network files, you want those devices to be always ready to respond.even if they consume a little more.

Additionally, network speed plays a role. If you're on a congested WiFi network, experiencing interference, or using a limited router, transferring metadata and file listings can be much slower than on a wired network.Connecting via Ethernet cable usually improves the response of network folders significantly.

The role of antivirus and other resident programs

A fairly typical cause of a folder taking a long time to calculate is the antivirus. Every time you access a directory, many antivirus programs scan the files to ensure there is no malware.If the folder has many items, or some of them are "suspicious" due to their type or size, the analysis may be constant.

To check if the problem originates there, you can temporarily disable your antivirus (either Windows Defender or a third-party one) and reopen the problematic folder. If everything suddenly loads quickly and the size calculation is almost instantaneous, it's pretty clear that real-time scanning is responsible..

The sensible solution is not to leave the equipment unprotected, but to use exclusion lists. Almost all antivirus programs allow you to exclude specific folders from real-time scans.Adding very large working directories or folders with files that you know are safe can greatly reduce the load on Explorer.

However, it must be done sensibly: If a file repeatedly triggers antivirus alerts, it's worth analyzing it thoroughly before ignoring it.Exclusions are a useful tool for improving performance, but also a potential security vulnerability if they are abused without proper judgment.

CPU, temperature and overall system status

On high-end computers, it may be surprising that only the Explorer seems to be slow, but the explanation sometimes lies in the temperature or in an abnormal use of the processor. When the CPU overheats, protection mechanisms such as thermal throttling come into play, reducing its frequency to lower the temperature..

When that happens, any task that is heavily dependent on the processor (such as calculating sizes, generating thumbnails, or processing metadata) becomes much slower. If the equipment is full of dust, has dirty fans, or insufficient cooling, it's quite likely that the temperature will spike even if the apparent CPU usage isn't extreme..

It is advisable to monitor the temperature using tools such as the Task Manager, the BIOS/UEFI, or third-party programs like HWMonitor. If the CPU regularly exceeds 85-90°C even under light loads, something is wrong with the cooling system..

Physically cleaning the inside of the equipment, replacing thermal paste on older processors, or improving airflow (adding fans, relocating cables, using cooling pads on laptops or external fans on mini PCs) can make a big difference. When the CPU returns to its normal frequency, the Explorer also becomes much smoother..

Additionally, reviewing the applications that load at startup and eliminating unnecessary processes helps prevent the processor from always being "busy" with residual tasks. The less unnecessary load the CPU has, the more headroom it will have to deal with intensive operations such as managing large folders..

When nothing else is enough: alternative file explorers

If after trying all these measures you are still frustrated with the slowness of Explorer, there is another practical approach: use third-party tools designed to work with large volumes of files. There are alternative browsers that are lighter, offer advanced features, and in many situations, respond faster than Windows Explorer itself..

One of the classic options is My Commander. It is a very lightweight file manager, with an integrated search engine, filters, bulk renaming, advanced views, and several features designed for users who manage many directories.Its strength lies in its low resource consumption and focus on speed.

Another interesting alternative is Explorer++A portable, fast, and simple browser. It allows you to work with multiple folders at once using tabs, change views, search for files, and customize many aspects of the interface.It's a good choice if you want something similar to the traditional Explorer, but with some extras.

For those who prefer a modern application integrated with the system, the Files app (available in the Microsoft Store) offers a UWP-like experience. It includes tabs, tags, column and dual-pane views, cloud integration, file preview, and customizable themes., with a fairly tight resource consumption.

Finally, if your work involves continuously moving and copying files between locations, Double Commander is a very powerful option. Its dual panel allows you to drag files between folders without having to open multiple windows, and it has many extra features for advanced users.However, in return it may consume slightly more resources in very intensive operations.

The reason Windows takes so long to calculate the size of a folder is usually a mixture of how the file system works, the state of the disk, the CPU load, the Explorer configuration and the influence of third-party programs; Reviewing basic maintenance, adjusting folder options, checking antivirus software, and, if necessary, using alternative file explorers allows managing large folders to go from a chore to a much more manageable task..