Excel formula checker
Paste a formula. This page tells you what it does and what looks wrong with it. Add a few rows of your own data and it will run the formula on them.
It is rules, not a model
This checker is the same code that marks the lessons on this site. It is a parser and a set of rules. So it knows exactly which 92 functions it implements and which it does not. When it meets one it does not know, it says so instead of guessing. Your formula and your data stay in your browser. Nothing is sent to a server, and there is no limit on how many times you use it.
What it can tell you
- Read the functions, the cells and the ranges a formula uses
- Count the arguments a function was given, against what it takes
- Find a bracket that was never closed
- Catch a VLOOKUP asking for a column past the end of its range
- Run the formula on rows you paste, and show what it comes to
- Name the Excel error it produces, and what that error means
What it cannot
A checker that only lists what it does well is telling you half of it. These are the limits. The page says which one it has hit, rather than calling your formula wrong.
- Read a reference to another sheet, or to a named table
- Read a whole-column reference like A:A
- Run a function outside the 92 it implements
- Spill a list of values down the sheet the way Excel does
- Tell you what you meant, when two different formulas look the same
Why a formula can look right and be wrong
The Excel mistakes that cost the most are the ones that produce no error. A lookup with the fourth argument left off returns the nearest smaller value instead of nothing. A total that skips a number stored as text still looks like a total. This is why the checker runs your formula on your own rows when you give them. The shape of a formula cannot tell you the answer is wrong. The answer can.
Practise the ones you got wrong
Reading why a formula is wrong is not the same as being able to write it next time. Each lesson is a real sheet you type into. It is marked by the rules on this page.