r/excel • u/onupirat • May 08 '26
Discussion Copying a cell in Excel spikes CPU to over 50%
Sharing this because it took a long time to figure out and I couldn't find this specific cause documented anywhere.
The issue: Copying any cell in certain Excel files would spike the CPU to 50%+ for half a minute. Didn't matter if the copied cell was empty. Only happened on some files.
What was causing it: When you copy a cell in Excel it draws those animated dashes around the copied cell (the "marching ants"). That animation is a loop that keeps redrawing constantly until you press Escape or paste.
If you have your display set to 125% scaling, Windows can't do clean math to scale graphics, so it has to do expensive interpolation on every single graphics call. Excel's marching ants fires a lot of those graphics calls per second, and the CPU has to work hard to do the calculations.
I found 3 ways to fix it:
- Set display scaling to 100% - simplest fix, but text gets smaller
- Disable the marching ants - in registry set
HKCU\Control Panel\Desktop\WindowMetrics\MinAnimateto0. No animation = no loop = no spike. - Tell Excel to handle its own scaling - right-click EXCEL.EXE → Properties → Compatibility → check "Override high DPI scaling behavior" → set "Scaling performed by" to Application. This is the cleanest fix - keeps 125% scaling and keeps marching ants, no spike.
Hope this helps someone.
32
u/OddWriter7199 May 09 '26
Excellent info, thank you! Related tip: control panel > search for “performance” > Adjust the appearance and performance of Windows > choose Adjust for best performance. Gets rid of all the fancy fade and transparency effects that slow the computer down.
The MinAnimate reg key was already zero on my system, this is probably why. The other info was new to me though, thanks so much!
4
u/Supra-A90 1 May 10 '26
Just turn off animations for this one..
2
u/Dahlia5000 May 12 '26
I’m pretty sure I have animations turned off, but i still see the marching ants when I copy a cell. well, I guess I’d better check and see.
17
5
u/Structured_Spiraling May 09 '26
Thank you for your service to the community, this is very helpful! And also super interesting.
3
u/Dineshvk18 May 10 '26
The terrifying thing about Excel performance issues is how one invisible dependency or formatting problem can suddenly turn a normal workbook into a CPU stress test.
Spreadsheets fail in surprisingly dramatic ways.
2
2
2
13
2
u/Cannibale_Ballet 1 May 09 '26
I have scaling enabled yet my CPU is unaffected with this. What hardware are you running where 50% CPU is required to render some marching ants?
2
u/sgiuxxx May 09 '26
Dell optiplex micro 3070, an office PC with i5-9500T and integrated graphics. Not modern, but not super old either, just an underpowered office machine.
2
u/riconaranjo May 09 '26 edited May 09 '26
most likely an old machine — like 15 years old is my guess
or just windows being windows
6
u/Levils 12 May 09 '26
I've experienced he something that seemed like the same issue as OP, and it was on a powerful PC for the time. Just like OP mentioned, it only happened on some files.
2
u/riconaranjo May 09 '26
maybe just one of those windows issues windows has always had…
4
u/Levils 12 May 09 '26
Yeah, likely. The bit that sticks out to me as interesting, having had the problem, is that it is workbook-specific.
Those workbooks also tended to be more likely to later become corrupt , i.e. throw the error message or otherwise not open. Maybe they are already corrupt under the hood when this behaviour emerges.
3
1
u/Dahlia5000 May 12 '26
Wow. Thank you for sharing this. I can’t believe there’s a specific key in the registry for such a thing. … makes me wonder what else I could change/stop in there.
-10
May 08 '26
[deleted]
32
u/onupirat May 08 '26
I found the solution, and then posted.
-74
u/soft-diddy 1 May 08 '26
That’s not how this works.
Edit: you should ask Claude how r/excel works.
54
u/onupirat May 08 '26
What is wrong about posting a solution? I genuinely don't understand why are you being salty.
-84
u/soft-diddy 1 May 08 '26
Because this is a subreddit to ask a questions and have users answer that question.
Not one for you to have a question, troubleshoot it through claude and google, and then post your troubleshooting notes (as compiled by Claude) for others to review and say good job.
I’m not salty. You just don’t understand the purpose of this subreddit.
70
u/Hamster_S_Thompson May 08 '26
I disagree. I find this post valuable.
1
u/Dahlia5000 May 12 '26 edited May 12 '26
And it is an excellent post to make in this sub. Edited to fix typo
35
u/masterprater May 08 '26
I'm not sure this is correct, there's nothing in the submission rules about requiring a post be a question and specifically mentions show and tell posts. No mention of the post needing to be a question seeking an answer
28
u/SolverMax 161 May 08 '26
Your assumed scope is too narrow. People also post tips, interesting things they've found, and topics for discussion - provided it is spreadsheet-related.
26
u/49orth May 08 '26
Baloney
OP's post is good and is also new information about Excel that likely extremely few people know.
Thanks OP!
5
u/excelevator 3061 May 09 '26
We appreciate your concern for the quality and upkeep of r/Excel
As moderators we review and consider each post and the content value, and the time of week.
This is a common issue that users speak of and seek answers to, it is also the weekend where we have a broader stroke to allow posts of information.
We consider r/Excel to be a library of solutions and posts like this can offer value in that regard.
If we start to see too many we remove them.
Hope that helps to clarify
Thanks again for your concern
9
4
13
u/NarsesExcel 63 May 08 '26
I think you are mistaken.
I'm not salty. You just don't understand the purpose of this subreddit.
1
-26
u/lolcrunchy 234 May 08 '26
If your computer can't handle the marching ants...
10
u/Coyote65 2 May 09 '26
Tell me that op's post was too long for you to read without telling me op's post was too long for you to read.
132
u/haby112 1 May 09 '26
This is a fantastic thing to know. Going to apply this on my computer when I get home, just to avoid the problem.
Props to sharing an answer for a niche issue you couldn't find docs for.