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How to Fix Excel High CPU Usage and Threading Issues
Question details
The user is experiencing severe performance issues, including freezing and near 100% CPU usage, when attempting to open a specific large workbook that contains numerous formulas and external links.
- Product
- Microsoft Excel
- Device & OS
- not provided
- Scenario
- Opening and collaborating on a heavy spreadsheet stored in SharePoint or Microsoft Teams.
- Observed behavior
- Excel runs extremely slowly, frequently stops responding, and consumes maximum CPU resources, especially during cloud synchronization.
Ensure your computer meets the recommended system requirements for handling heavy spreadsheets, and temporarily pause any background antivirus scans that might be inspecting the workbook as it opens.
Move and Test the Workbook Locally
Determine if the high CPU usage is caused by SharePoint or Microsoft Teams synchronization delays.
Network latency and real-time cloud synchronization can heavily strain Excel's processing threads. Isolating the file to your local machine helps identify whether the issue is network-related or file-related.
Navigate to your SharePoint or Teams folder, right-click the affected workbook, and select 'Download' to save a copy directly to your local desktop.
Temporarily pause your OneDrive or SharePoint synchronization by clicking the cloud icon in your system tray, selecting the gear icon, and choosing 'Pause syncing'.
Open the local copy of the workbook from your hard drive. Press Ctrl + Shift + Esc to open the Task Manager and monitor if Excel's CPU usage normalizes.
Optimize Formulas and Remove External Links
Minimize the calculation burden on Excel's calculation threads to lower CPU usage.
Experience Faster Spreadsheet Performance with WPS Office
If Microsoft Excel continues to struggle with high CPU usage and synchronization freezes, consider switching to WPS Office. It is a highly optimized, lightweight alternative designed to handle complex spreadsheets efficiently without overloading your system.
- 1. Install WPS Office: Download and install the free WPS Office suite on your computer.
- 2. Open WPS Spreadsheet: Launch the application and select 'Spreadsheet' from the main dashboard.
- 3. Load Your File: Click 'Open' and select your heavy .xlsx file to experience smooth, lag-free editing.
Frequently Asked Questions
What causes Excel to use 100% CPU when opening a file?
High CPU usage is typically caused by Excel processing thousands of complex array formulas, attempting to update broken external links, or struggling with real-time background synchronization overhead from network drives like SharePoint and Teams.
How do I change the number of calculation threads in Excel?
Go to File > Options > Advanced. Scroll down to the 'Formulas' section. Under 'Enable multi-threaded calculation', you can manually set the number of calculation threads to limit Excel's CPU usage to fewer cores.
Does file size directly affect Excel's CPU consumption?
Not necessarily. A smaller file heavily packed with volatile functions (like OFFSET or INDIRECT) and complex conditional formatting can consume far more CPU resources than a massive file containing only plain static text and numbers.
Why does Excel lag more when working out of SharePoint or Teams?
When collaborating on SharePoint or Teams, Excel continuously syncs changes with the cloud. If network latency is high or multiple users are making edits simultaneously, this constant background data transfer can bottleneck the application and spike CPU usage.
