A quick sum without uploading the file anywhere
Somebody sends you six rows in an email and asks what the total is with tax. The honest options are all slightly annoying: open a desktop spreadsheet and wrestle with the paste, or drop the rows into whichever free online converter is top of the search results. The second one is quick, and it involves handing a stranger's server a list of what your company bought.
The third option is a formula evaluator that runs in the page. You paste CSV, any cell may begin with =, and you get the evaluated grid back. Nothing is uploaded — the calculation happens in your browser, which is the only reason pasting real rows into a web page is a reasonable thing to do.
The worked example
Paste this, exactly as it is:
item,qty,price,lineCable,3,4.50,=B2*C2Adapter,2,12.00,=B3*C3Case,1,19.99,=B4*C4Subtotal,,,=SUM(D2:D4)Tax,,,"=ROUND(D5*0.07,2)"Total,,,=D5+D6
The evaluated CSV that comes back is:
Cable,3,4.5,13.5Adapter,2,12,24Case,1,19.99,19.99Subtotal,,,57.49Tax,,,4.02Total,,,61.516 formula(s), 0 error(s).
Check it on paper: 3 × 4.50 = 13.50, 2 × 12 = 24, 1 × 19.99 = 19.99, and 13.50 + 24 + 19.99 = 57.49. Tax is 57.49 × 0.07 = 4.0243, rounded to 4.02, and 57.49 + 4.02 = 61.51.
Two details in that output are the method, not the tool. The row numbers are the CSV's own row numbers, so the header is row 1 and the first data row is row 2 — which is why the first formula reads B2*C2. And the quotes around "=ROUND(D5*0.07,2)" are ordinary CSV quoting: the formula contains a comma, so without them the comma would be read as a new column.
Ask it to show its working
Name a cell and it prints the source and the value:
D5source: =SUM(D2:D4)value: 57.49
That is the check worth doing on any total you did not write yourself. A number in a cell tells you nothing about where it came from; the formula behind it tells you everything.
Errors that stay errors
Break the same sheet deliberately — a quantity typed as two, and a division by an empty cell:
Adapter,two,12.00,=B3*C3Rate,,,=D2/E2
The real output is:
3 formula(s), 2 error(s).D3 =B3*C3 #VALUE! (wrong type, or the formula could not be read)D4 =D2/E2 #DIV/0! (divided by zero)
This is the behaviour that makes a small tool trustworthy. A bad value stays visible as an error and propagates into anything that reads it, rather than quietly becoming zero and dragging an average down without explaining why. Circular references are caught too, and reported as #CYCLE! instead of hanging the page.
Where it stops, honestly
This is the calculating part of a spreadsheet and nothing else. It knows nineteen functions: SUM, AVERAGE, MIN, MAX, COUNT, COUNTA, ROUND, ABS, IF, AND, OR, NOT, CONCAT, LEN, UPPER, LOWER, TRIM, SUMIF and COUNTIF. Anything else — VLOOKUP, any date function, any text-splitting function — returns #NAME? rather than pretending to work.
There are no saved sheets, no tabs, no charts, no formatting, no cell colours and no undo. It takes pasted CSV, not an uploaded file; it gives back CSV and a plain table. Close the tab and it is gone, which is the same property as the privacy: it holds nothing because it stores nothing.
SUMIF and COUNTIF take a number, a text value or a comparison such as >10 or <>done as the criterion. Asterisks and question marks are matched literally, not as wildcards.
Arithmetic is double-precision floating point, as it is in every spreadsheet, so round explicitly at the point where money becomes money — which is what ROUND(D5*0.07,2) above is doing. The display rounds to ten decimal places, and that rounding never feeds another calculation.
The ceiling is 1,000 rows and 100 columns, and unlike some tools it tells you when you hit one rather than truncating in silence. Still: this is for the six rows in an email, the twenty-line invoice check, the quick column of figures you do not want to email to a converter. A file with real size in it belongs in a real spreadsheet application or a database.
The Spreadsheet Lite formula evaluator is that narrow job done properly. Knowing which cell reference points where, and quoting a formula that contains a comma, is the part you keep.