A spreadsheet does not fail. It returns a plausible wrong answer.

Part 2

What the function actually does

Lookup, arrays, references and recalculation, each stated with the version it was established on.

7 of 7 written

Part 4

A file that survives a year

Arrangements that make a mistake visible instead of letting it travel into a report.

7 of 7 written

Part 6

Establishing that it is not lying

Tracing, cross-footing, validation, review, and the point at which the work should leave the sheet.

7 of 7 written

Written so far

What a recipe without a version costs you

Behaviour differs between Excel for Windows, Excel for Mac, Excel on the web, the perpetual-licence versions and Google Sheets, and it differs in ways that decide whether an instruction works at all. The newer lookup function does not exist before Excel 2021. Formulas that expand into neighbouring cells do not exist before that either, and a file using them opens with errors. Defining your own function is in Excel 365 and not in Excel 2021. Structured references into a table exist in one product and not in the other at all.

Dates, separators and number parsing depend on the locale of the machine rather than on anything in the file, so the same instruction produces different data for two colleagues in two countries, with both installations behaving exactly as documented.

A guide that omits the label is not being brief. It is making a claim about nothing in particular, and a reader who follows it finds out at the first step or, worse, at the step after that.

The four things that go wrong most

A range that stops short. A formula written when the data was shorter, or a selection that ended a few rows early. It computes correctly and it answers a question about part of the data.

A function doing what it was told rather than what was meant. The most used lookup in this field matches approximately unless told otherwise, so a key that is absent returns a real value belonging to another row.

Data changed on the way in. Leading zeros removed, a sixteen-digit identifier truncated, a product code read as a date. All decided at the moment of arrival, and the original characters are not stored anywhere afterwards.

A formula somebody typed over. One cell in a calculated column now holds a constant. It looks identical to its neighbours and it will never change again, whatever happens upstream.

How every entry is written

The mechanism first. The point of an entry is why the behaviour is what it is, so that a reader can predict the next case rather than memorise this one. A recipe that works and is not understood fails silently the moment the circumstances differ slightly, which on this subject is most of the time.

Every documented failure is traced to a primary source: an official report, a regulatory filing, a published investigation. Where only press coverage exists, the entry says so. Research into how many spreadsheets contain errors exists, disagrees with itself depending on method, and is not quoted here.

And every entry ends with what it cannot verify, including the places where a behaviour was established by testing rather than found in documentation, and the places where the vendors document one product better than the other.

Why this domain

This address previously belonged to a floral design studio, which closed under this name. Recalc has no connection to it, to its owner, or to anything she does now, and none of the former site's material appears here. Every address from it has been withdrawn.

Tools for spreadsheet teams

Three comparisons for teams coordinating spreadsheet work, review evidence and time records.

For further context, see Microsoft's Excel fundamentals.