Quick answer
If numbers won't update, calculation is set to Manual — go to Formulas → Calculation Options → Automatic, or press F9 to recalculate now. If a cell shows the formula text instead of the answer, the cell is formatted as Text (change it to General and re-enter it) or Show Formulas is switched on (press Ctrl + `).
WHY IT HAPPENS
Different symptoms, different causes.
There are two separate problems people lump together. If your formulas simply don't recalculate when data changes, that's the calculation mode. If a cell literally displays the formula (like =SUM(A1:A10) as text), that's a formatting or view setting. And if Excel warns about a circular reference, a formula is pointing back at itself and can't finish. Match your symptom below and fix the right one.
THE FIX
Check these in order.
- Set calculation back to AutomaticIf nothing updates when you change numbers, calculation is set to Manual. Go to the Formulas tab → Calculation Options → choose Automatic. To force a recalculation right now, press F9 (or Ctrl + Alt + F9 to recalculate everything). Manual mode is often switched on by an add-in or carried over from another file, so it can appear without you doing it.
- Check the cell isn't formatted as TextIf a cell shows the formula as words, click it and look at the Number group on the Home tab — if it says Text, that's the problem. Change it to General, then click into the cell, press F2 and Enter to re-enter the formula so Excel calculates it.
- Turn off Show FormulasIf every formula on the sheet shows its text instead of a result, Show Formulas is on. Press Ctrl + ` (the backtick key, top-left below Esc) to toggle it off — or untick Formulas → Show Formulas. Nothing is broken; it's just a display mode for auditing.
- Remove a leading apostropheAn apostrophe at the very start of a cell ('=SUM(...)) tells Excel to treat the whole thing as plain text. It won't show in the cell but you'll see it in the formula bar. Delete the apostrophe and press Enter, and the formula will calculate.
- Fix circular referencesIf Excel warns of a circular reference, a formula refers back to its own cell (for example, D3 contains =D1+D2+D3). Go to Formulas → Error Checking → Circular References to see the cells involved, then edit each so it no longer includes its own cell.
- Check for a space or hidden characterIf a formula still won't work, make sure there's no space before the = sign and no stray characters pasted in from an email or web page. Re-typing the formula from scratch in a clean cell is the quickest way to rule this out.
Working with financial models or reporting? When a whole spreadsheet full of numbers is wrong, it's often one of these settings quietly flipped — but on shared workbooks it can also point to a broken link, a bad add-in or corrupted data. If it keeps happening across your team, it's worth having someone check the underlying setup rather than fixing each file by hand.