How to Fix Slow Excel Calculation on Mac with Low CPU Usage
Question details
Users experience extremely slow workbook calculation times in Excel for Mac, even though the application uses only a small fraction of the available multi-core CPU resources.
- Product
- Microsoft Excel for Mac
- Device & OS
- macOS
- Scenario
- Calculating large data tables or workbooks with complex, interdependent formulas.
- Observed behavior
- Excel takes an unusually long time to calculate (e.g., over 30 seconds for a large table) while Activity Monitor shows it is only utilizing 1 or 2 CPU cores out of a high-core-count processor, leaving most system resources idle.
Ensure your macOS is fully updated and temporarily move your Excel workbook from any cloud or network server to your local Mac hard drive to rule out network latency.
Reset Excel Preferences and Clear the Container Cache
Removing potentially corrupted preference files can resolve application glitches that prevent Excel from properly allocating CPU threads for calculation tasks.
Sometimes, Excel's system preference files become corrupted, causing the application to fail at properly utilizing multi-core processing. On newer macOS versions like Ventura, the file paths might differ slightly from older OS versions.
Ensure Microsoft Excel is completely closed. Right-click the Excel icon in your Dock and select 'Quit'.
Open Finder, press Command + Shift + G, and enter '~/Library/Preferences/'. Look for 'com.microsoft.office.plist' or 'com.microsoft.Excel.plist' and drag it to your Desktop.
Press Command + Shift + G again and enter '~/Library/Containers/'. Locate the folder named 'Microsoft Excel' (or 'com.microsoft.Excel' on older OS versions) and move it to your Desktop.
Relaunch Excel. This forces the app to rebuild its default preferences. Open your large workbook and trigger a calculation to see if CPU usage improves.
Disable Add-ins and Test Mac in Safe Mode
Third-party extensions, macros, or background background programs might be throttling Excel's calculation speed.
Optimize Workbook Structure for Multi-core Processing
Excel's calculation engine may fail to trigger parallel processing if formulas are highly interdependent.
Try WPS Office for Fast and Lightweight Spreadsheet Processing
If Microsoft Excel continues to struggle with multi-core processing or performance throttling on your Mac, WPS Office offers a lightweight, highly optimized alternative. It fully supports standard spreadsheet formats and handles complex data tables with excellent speed and efficiency.
Frequently Asked Questions
Why is Excel using only one CPU core during calculation on my Mac?
This usually happens when your workbook contains interdependent formulas that must be calculated sequentially, preventing Excel from utilizing multi-threaded calculation. Corrupted user preferences or unoptimized data tables can also cause this bottleneck.
Does disabling macros improve Excel calculation speed?
Yes, if a macro is poorly optimized or constantly triggered by worksheet calculation events (such as Worksheet_Calculate), it can severely slow down performance. Disabling macros temporarily helps determine if they are the root cause.
How do I ensure multi-threaded calculation is enabled in Excel for Mac?
Click on 'Excel' in the top menu bar, select 'Preferences', and click on 'Calculation'. Under the calculation options, ensure that 'Enable multi-threaded calculation' is checked and set to use the maximum number of available processors.
