Speed Up a Slow Excel Workbook Without Rebuilding It

By / Last Updated October 15, 2026

A slow workbook can usually be made fast without changing how it looks or works: an Excel VBA developer finds what makes it slow, fixes those parts, and measures the difference.

The issue

Our scheduling workbook has grown over the years and is now painfully slow. It takes almost a minute to open, freezes for several seconds every time someone changes a cell or applies a filter, and the macro that builds the weekly roster runs for minutes. Everyone depends on it, so we can’t start over.

We need someone to find out why it’s slow and make it fast again, without changing how the sheets look or how we use them.

How I’d build it

Yes, I can definitely speed this up for you.

First I find where the time goes. I time how long the workbook takes to open, to recalculate and to run each macro, then go through it sheet by sheet. In older workbooks the time usually comes from a handful of things: the same lookup repeated in every column, functions such as INDIRECT and OFFSET that recalculate on every change, conditional formatting rules that have been copied thousands of times, and macros that select cells one at a time.

An Excel sheet titled Speed Check. A line at the top reads: Scheduling workbook, 38.4 MB, opens in 47 seconds, recalculates for 9 seconds after any change. Below it, seven findings, each with the sheet, what slows it down, how much of it there is, a colored effect (High, Medium or Low) and the fix. The first is the same exact-match VLOOKUP repeated in each column, in 2,400 cells, fixed by finding each row once with MATCH and reading it with INDEX.
Illustration with sample data: the Speed Check, what makes the workbook slow and the fix for each.

Then I fix those parts and leave everything else as it is.

1 Each row is looked up once instead of once per column, formulas are pointed at the rows that hold data, and functions that recalculate on every change are replaced with ones that recalculate only when their inputs change.

2 Duplicate formatting rules and unused styles are cleared out, which also makes the file smaller.

3 The macros are rewritten to read and write the data in one pass instead of cell by cell, so a run that took minutes usually takes seconds.

An Excel sheet titled Before and After, five tasks timed on the same workbook: opening it went from 47 seconds to 5 seconds, recalculating after a change from 9.0 seconds to 0.3 seconds, applying a filter from 6.5 seconds to 0.2 seconds, the Build Roster macro from 3 min 12 sec to 8 seconds, and the file size from 38.4 MB to 6.1 MB, each change shaded green.
Illustration with sample data: the same tasks timed before and after.

You get the same workbook back, with the same sheets, buttons and layout, plus a short list of what changed and the before and after timings, so you can see the difference for yourself.

To get started, describe your file below. Once I reply, you can send a copy of the workbook (sample data is fine).

Small fixes start at $69.

Every project gets a fixed-price quote before any work starts: the price you approve is the price you pay.

Step 1 of 2

What can we help you with?

A few words is enough. You can add more once we reply.

Pick the closest match (optional)

Helpful to include:

  • What you do today
  • What you want it to do instead
  • Anything you have already tried

Have a sample workbook or a screenshot? Attach it when you reply to our first email. A copy with confidential data removed is fine.

When do you need it?
Do you use Excel on Windows or Mac? (optional)

One more short step: your name and email.

Related Excel Tips

Why .Select and .Activate Make Your VBA Slow → How to Loop Through Rows in VBA Without Freezing Excel → Why INDEX/MATCH is Better Than VLOOKUP for Complex Lookups → Excel Workbook Rescue: Fix a Broken or Slow Workbook →
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