About this article
This article is generated through an automated workflow utilizing generative AI. It reviews the Microsoft Support specifications for the LET function and uses dummy data to organize how to break down long Excel formulas into intermediate results for verification.Verification Status: 📘 Microsoft Official Specifications Confirmed / Excel Device Testing Pending
Rather than trying to make long Excel formulas shorter, it is easier to fix them byassigning names to intermediate results so they are visible. The LET function allows you to assign names to calculation results and reuse them within the same formula.
Try it first
Assuming sales are in A2 and the tax rate is in B2, enter the following.
=LET(税抜,A2,税額,税抜*B2,税抜+税額)
If A2 = 1000 and B2 = 0.1, the final result will be 1100.
Look here
The final argument of LET is the return value. When you want to verify calculations, change only the last part.
=LET(税抜,A2,税額,税抜*B2,税額)
This way, you can see 100. In other words, you can isolate whether the issue lies in the "final result being incorrect" or "the process of generating the tax amount being incorrect."
Why it is useful
When you read through long IF or XLOOKUP statements all at once, the same expressions appear repeatedly. By assigning names with LET like 検索値、候補、判定, formulas start to resemble a sequence of smaller operations.
graph LR A[入力] --> B[途中結果1] B --> C[途中結果2] C --> D[最終結果]
Change one part
Sequentially change the final return value to 税抜 → 税額 → 税抜+税額. Even without a code debugger, you can observe intermediate values one by one.
When using it at work
It is particularly effective for cells where "the formula works, but nobody wants to touch it," such as billing amounts, allowance calculations, code conversions, and multi-condition evaluations. Naming variables using business terminology like x1 rather than 対象日、単価、判定結果 makes handovers much easier.
However, cramming too much into LET can make it harder to read. If the business logic is large, consider comparing it with auxiliary columns, Power Query, or separating it into VBA/Office Scripts.
Summary
The LET function is not just a feature for shortening formulas.Being able to extract intermediate values with names for verification is a major advantage in administrative work.
Official Information / Primary Sources
- Microsoft Support LET function: https://support.microsoft.com/ja-jp/office/let-%E9%96%A2%E6%95%B0-34842dd8-b92b-4d3f-b325-b8b8f9908999
