Microsoft Excel 1.0 was released in 1985, 40 years ago. Since then, Excel has evolved with new functions and features. In our view, the most significant recent change to Excel is the introduction of Dynamic Arrays, along with the release of associated new worksheet functions, which have fundamentally changed how formulae work.
Of the new functions introduced in the last few years, we believe that the LET and LAMBDA functions are the most important because they can dramatically change the way users write formulae.
But there's a price to be paid for the new functions: we're concerned that they encourage users to write long, complex formulae. As discussed in our good practice guideline Keep formulae simple, long and complex formulae are problematic and are best avoided. Specifically, research has demonstrated that long and complex formulae are harder to understand, more difficult to correctly modify, and are more error prone.
To see if our concern has materialized, we examine current Excel worksheet function usage. We're especially interested in how the usage of LET and LAMBDA functions differs from the usage of other functions in formulae.
Therefore, in this article, we explore a new corpus of Excel formulae that we have collated: the 2025 Reddit Excel Formula Corpus.
We focus on four metrics:
- Identifying the most commonly used functions.
- Usage of related functions.
- The number of functions per formula.
- Formula length, in characters.
For each of these metrics, we describe and compare statistics for the 2025 Reddit Excel Formula Corpus formulae overall, formulae that exclude the LET and LAMBDA functions, and formulae that use the LET and LAMBDA functions. We also compare the most commonly used functions in the new corpus with earlier lists of commonly used functions, to see how function usage has changed.
2025 Reddit Excel Formula Corpus
Sample of formulae from Reddit's Excel forum
To gather data about current formula and function usage, we examined all posts and comments in the Excel forum on Reddit for the month of May 2025. We extracted worksheet formulae to form what we call the "2025 Reddit Excel Formula Corpus".
We looked at 1,332 Reddit posts over the month, of which 806 (60.5%) mention worksheet functions and 682 (51.2%) contain formulae. We ignored posts that don't mention functions – those posts cover a wide range of topics, including: VBA, Power Query, data management, business processes, and many others. Almost 10% of posts mention one or more functions not in the context of a recognizable formula. From the 682 posts (and associated comments) that contain one or more formulae, we extracted 2,151 formulae which use functions 7,732 times. Note that if a function appears multiple times in a formula, then it is counted multiple times. It is on these functions and formulae that we focus our analysis.
Caveats: The data source is messy
The function and formula extraction process was semi-automated, with considerable automatic and manual data cleansing. The extraction was for the calendar month of May 2025, with each day defined using Coordinated Universal Time. We extracted data at least two days after the date of each post, to allow time for users to comment and make edits. Users may make edits and additional comments indefinitely, so it is possible that some edits and comments were missed by the extraction process.
We ignore VBA, Power Query, obsolete Excel 4 Macro functions, and functions that are available in Google Sheets but not Excel. We also ignore images, some of which may contain formulae.
Four examples of formulae are shown in Figure 1, showing how they are presented in a variety of formats and contexts. Formulae may be in <code> or <pre> HTML tags, or embedded in free-form text with or without tags. Consequently, extraction of functions and formulae is somewhat imprecise. In addition, some extracted formulae are not valid Excel formulae, being either indicative of what could be done or containing syntax errors.
Given the messy nature of the data, and despite our attempts at data cleansing, the corpus certainly contains errors and omissions. Nonetheless, we believe that it achieves our goal of being a good sample of current function and formula usage in the Reddit Excel community. Whether or not the corpus is representative of broader Excel usage is a different question.
Analysis of the 2025 Reddit Excel Formula Corpus
Most commonly used functions, all formulae
We're primarily interested in the functions users apply in their formulae. So, Figure 2 lists the top 20 functions used in the 2025 Reddit Excel Formula Corpus.
In this group, there are 2,151 formulae that use functions 7,732 times, for an average of 3.6 functions per formula.
The IF function is, by a significant margin, the most commonly used function, with 586 out of 7,732 function uses (7.6%). The next three most common functions are all relatively new: FILTER (introduced in 2021), LET (2020) and LAMBDA (2020). There are also some other relatively new functions in the top 20, along with old favourites like SUM and TODAY.
The top 20 functions account for 52.6% of all function uses in the corpus. The top 49 functions account for 80%, and the top 94 functions account for 95% of all function uses.
Of the 520 functions in Excel, as of May 2025, only 184 (35.4%) appear in the corpus.
Comparison with other lists of commonly used functions
It is useful to compare our list of most commonly used functions with earlier lists, specifically:
- A 2019 list of popular functions by Microsoft. See Excel functions, our 10 most popular functions.
- The FUSE corpus, which collated 249,376 spreadsheets from the Web in 2015. See Fuse: A reproducible, extendable, internet-scale corpus of spreadsheets and VBA in the spreadsheets from the FUSE corpus.
- A corpus of 9,120 spreadsheets containing formulae, extracted from Enron Corporation's email archive in 2013. See Enron's spreadsheets and related emails: A dataset and analysis.
- A corpus of 1,961 spreadsheets containing formulae, via Google search in 2005. See The EUSES spreadsheet corpus: A shared resource for supporting experimentation with spreadsheet dependability mechanisms.
The Enron corpus and the EUSES corpus are compared in Enron versus EUSES: A comparison of two spreadsheet corpora.
Figure 3 lists the most commonly used functions from each of those sources, compared with the 2025 Reddit Excel Formula Corpus. The functions that appear only once in the table are highlighted in green.
The 2025 Reddit Excel Formula Corpus differs markedly from the earlier lists. Of the top 20 functions in the 2025 Reddit Excel Formula Corpus, 13 functions (65%) do not appear in any of the earlier lists – reflecting the relative newness of those functions and illustrating how much formula construction has changed in recent years. Although the earlier lists differ from each other, depending on the context from which they were collated, they have much more similarly with each other than they do with the 2025 Reddit Excel Formula Corpus.
The SUM and IF functions are at the top of all the earlier lists. The VLOOKUP function is also highly or moderately ranked in the earlier lists, though it appears only at position 30 in the 2025 Reddit Excel Formula Corpus – having been largely replaced by the INDEX (usually in association with MATCH) and XLOOKUP functions.
Most commonly used functions, excluding LAMBDA and/or LET
In positions three and four of the most commonly used functions in the 2025 Reddit Excel Formula Corpus are the LET and LAMBDA functions respectively. When we look at formulae that do not use LET and/or LAMBDA functions, we get the list shown in Figure 4.
This set of commonly used functions is much more like the earlier lists shown in Figure 3, with the exception of newer functions such as FILTER (introduced in 2021) and XLOOKUP (2016). The IF function is even more prominent, at 10.2% of all function uses in this group.
This group of formulae, which exclude formulae that use LET and/or LAMBDA functions, is 80% of the total formulae and 54% of the functions in the 2025 Reddit Excel Formula Corpus. There are 1,723 formulae that use functions 4,159 times, for an average of 2.4 functions per formula.
Most commonly used functions, formulae that use LET and/or LAMBDA
Conversely, the distribution of functions used in formulae that do use LET and/or LAMBDA functions is very different, as shown in Figure 5. Of the top 20 functions (excluding LET and LAMBDA), 13 are different from those shown in Figure 4. Unsurprisingly, these formulae make greater use of functions that work with arrays, like DROP, CHOOSECOLS, and VSTACK.
This group of formulae, which include only formulae that use LET and/or LAMBDA functions, is 20% of the total formulae in the 2025 Reddit Excel Formula Corpus. There are 428 formulae that use functions (including LET and/or LAMBDA) 3,573 times, for an average of 8.3 functions per formula – more than three times as many compared with formulae that exclude LET and/or LAMBDA functions.
Note that we've combined formulae that use LET and/or LAMBDA functions. Looking at formulae that use LET and LAMBDA separately tells a broadly similar story.
Usage of related functions
Figure 6 shows some interesting groups of related functions. We also show the rate of occurrence per 1,000 functions in the 2025 Reddit Excel Formula Corpus (equal to 10 times the percentages in the previous figures).
Some observations:
- The
IFfunction is used 10 times as often as theIFSfunction. SUMis used far more often than its related functions combined.XLOOKUPis used more than four times as often asVLOOKUP. On the Reddit Excel forum, users are often advised to preferXLOOKUPoverVLOOKUP.- However,
XMATCHhas not quite taken over fromMATCH. - The
...IFSfunctions are used less often that their...IFequivalents – except forSUMIFS, which is used about a third more often thanSUMIF. CONCAThas largely taken over fromCONCATENATE(which exists for backwards compatibility reasons).- The functions designed for manipulating arrays, such as
CHOOSECOLS, etc. are widely used, especially in formulae that useLETand/orLAMBDA.
Functions per formula, all formulae
Figure 7 shows the distribution for the number of functions used per formula, including all formulae in the 2025 Reddit Excel Formula Corpus. The most common number of functions per formula is one, while the average is 3.6 functions per formula with a long tail. A small proportion (3.3%) of formulae have no functions, such as =((A2*3.65%)/12) and =$A$1*($B$3:$B$100). Only 0.9% of formulae use more than 20 functions.
Functions per formula, excluding formulae with LET and/or LAMBDA
Figure 8 shows the distribution for the number of functions used per formula, excluding formulae with LET and/or LAMBDA functions. The most common number of functions per formula is one, while the average is 2.4 functions per formula. There is a long tail again, but it is less pronounced than for all formulae. Around 0.3% of formulae use more than 20 functions.
Functions per formula, formulae that use LET and/or LAMBDA
Figure 9 shows the distribution for the number of functions used per formula, only including formulae with LET and/or LAMBDA functions. This distribution is very different, with the most common number of functions per formula being five (rather than one), and an average of 8.3 functions per formula. The long tail is much more substantial, with 3.5% of formulae using more than 20 functions.
Formula length, all formulae
Figure 10 shows the distribution of formula length, in characters, for all formulae in the 2025 Reddit Excel Formula Corpus. In calculating the length, multiple spaces (such as indents on new lines) have been trimmed.
The most common formula length is 31-40 characters, with 79.7% of formulae <= 100 characters. The average formula length is 77 characters. There is a long tail of formula lengths, with 2.9% of formulae being more than 300 characters long.
Formula length, excluding formulae with LET and/or LAMBDA
Figure 11 shows the distribution of formula length, in characters, excluding formulae with LET and/or LAMBDA functions. The most common formula length is 21-30 characters, with 91.0% of formulae <= 100 characters. The average formula length is 54 characters. There is a long tail of formula lengths, with 0.6% of formulae being more than 300 characters long.
Formula length, only formulae with LET and/or LAMBDA
Figure 12 shows the distribution of formula length, in characters, only including formulae with LET and/or LAMBDA functions. The most common formula length is 101-110 characters, with 34.3% of formulae <= 100 characters. The average formula length is 171 characters – more than three times longer the average for formulae that exclude LET and/or LAMBDA functions. There is a much longer and more substantial tail of formula lengths, with 12.1% of formulae being more than 300 characters long.
Summary of functions per formula and formula length
Figure 13 shows a summary of the functions per formula and formula length statistics described above.
Compared with formulae that do not use LET and/or LAMBDA function, on average the formulae that include LET and/or LAMBDA functions:
- Use 3.5 times as many functions (8.3 vs 2.4).
- Are 12.1 times more likely to use more than 20 functions per formula (3.50% vs 0.29%)
- Are 3.2 times longer (171 vs 54 characters).
- Have a length over 100 characters 7.3 times more often (65.6% vs 9.0%).
That is, long and complex formulae are a typical characteristic of formulae that use LET and/or LAMBDA functions. These metrics indicate that LET and LAMBDA functions have made a major change in the way some Excel users write formulae.
Download the 2025 Reddit Excel Formula Corpus
The 2025 Reddit Excel Formula Corpus is available at: 2025-Reddit-Excel-Formula-Corpus.xlsx.
Conclusion
In this article, we explore a new corpus of Excel formulae that we have collated: the 2025 Reddit Excel Formula Corpus.
We're especially interested in how the LET and LAMBDA functions have changed the usage of functions in formulae. Our main concern is that LET and LAMBDA functions may lead to long, complex formulae – contrary to our good practice guideline to Keep formulae simple.
The results are clear: LET and LAMBDA functions have substantially changed how users write formulae. Specifically, formulae that use LET and LAMBDA functions, on average, use 3.5 times as many functions, are 12.1 times more likely to use more than 20 functions per formula, are 3.2 times longer, and have a length over 100 characters 7.3 times more often. In summary, formulae that use LET and LAMBDA functions are substantially longer and more complex than other formulae A consequence is that such formulae are generally harder to understand, more difficult to correctly modify, and are more error prone.
Microsoft have added many useful functions in recent years, some of which enable users to simplify their formulae. But the tools for managing formulae have not kept up. While we appreciate the usefulness of the LET and LAMBDA functions in particular, Excel needs better tools for managing the complexity that they encourage.
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