Unit-aware Calculation Checker

Excel has no concept of a unit. =B4+C4 where B4 is 250 mm and C4 is 0.25 m returns 250.25, and nothing anywhere objects. Neither does mixing kN with N, or summing a moment in N·mm with one in kN·m.

This add-in reads the units you have already written — in column headers, row labels, units rows, number formats and cell notes — follows them through your formulas, and reports the places where two of them contradict each other.

What it finds

• A length added to an area. Or a force to a moment, or any other pair of quantities that cannot legally be added.
• kN summed with N. The same quantity in two different prefixes. The answer looks perfectly reasonable and is out by a factor of a thousand.
• A column that mixes units partway down.
• A header that contradicts its own formula — the column says kN, the formula produces kN·m.
• An IF returning different units from different branches, so whatever reads it cannot know which it got.

How it knows what the units are

Excel stores no units, so they have to be recovered from what you wrote near the number. In order of confidence: a unit you assign yourself; a custom number format such as 0.00" kN"; a column header such as Moment (kN·m); a row label such as Yield stress, MPa; a units row under the header; a cell note; a defined name such as Fy_MPa.

Every finding tells you which cells it read the two units from, and by which of those routes, so you can check the tool rather than take its word.

What it will not do

It never guesses. A cell with no unit it can read stays silent rather than being assumed. A symbol with more than one meaning — t for tonnes or thickness, lb for mass or force — is reported as unreadable rather than resolved by coin toss. A sheet with no units in it at all produces one message saying so, not a hundred findings.

It cannot tell torque from energy, or stress from pressure, or work from moment: those pairs are dimensionally identical and no dimensional check can separate them. It cannot catch a formula that is wrong but dimensionally valid. Every report says so in as many words. A clean result means no contradiction was found, not that the calculation is correct.

What it costs

Free, unlimited: checking the active sheet. Scanning and explaining one sheet is not a paid feature and will not become one. You should be able to watch this thing stay silent on a spreadsheet you know is right before you consider paying for it.

The paid tier adds the whole workbook at once, units you assign yourself saved into the file, the report as an inserted worksheet, and CSV export. Pricing is not published yet.

Your data

Nothing in your workbook leaves your machine. No formula, no cell, no sheet name. The add-in talks to one server and only ever about a licence key and an anonymous install id. Details in the privacy notice.

Known limits

• Structured table references, external workbook references, dynamic arrays, LET and LAMBDA are not interpreted. A formula using one is reported as unreadable rather than guessed at.
• Lookups (VLOOKUP, INDEX, XLOOKUP) produce an unknown unit, because which cell they will return cannot be known without running the sheet.
• Excel on Mac and on iPad are untested. The manifest permits them, so Microsoft lists them, but no verification run has happened on either. Please report anything odd.
• Temperatures are read but the difference between an absolute temperature and a temperature difference is not yet enforced.

Support

support@appgarden.co.uk. A sheet that produced a wrong finding is the most useful thing you can send, and the one I most want to see.