In Excel: go to File ▸ Info ▸ Protect Workbook ▸ Encrypt with Password, set a password, and the whole .xlsx then requires it to open.
Open File ▸ Info, click Protect Workbook, and choose Encrypt with Password.
Type a strong password, click OK, then re-enter it to confirm.
Save the file (Ctrl+S) so the encryption is written to disk.
Test it by closing and reopening the workbook — it should prompt for the password before opening.
What this does
Encrypting a workbook with a password locks the entire file so it cannot even be opened without the password — the contents are scrambled on disk, not merely set to read-only. This is workbook-level (file-level) encryption, reached through File ▸ Info ▸ Protect Workbook ▸ Encrypt with Password, and it is completely separate from sheet protection: it controls who can open the file at all, rather than which cells can be edited once it is open. The same idea underpins a lot of everyday Excel work, so the few minutes spent getting it right here pay back across every sheet you build afterwards. Treat it as a pattern, not a one-off, and it stops being something you look up and starts being something you reach for. The difference between a quick fix and a sheet you can trust is the extra minute you spend validating “password protect a zipped excel file”. Start on a copy or a tiny sample, keep the affected cells visible, and compare the result with the tool above before you touch the real workbook. When this is a ribbon command, the selection matters more than the button: confirm the range, apply the command, then spot-check the output before saving. The point is a workspace setting that makes a big sheet comfortable to navigate, but the practical win is that someone else can open the file and understand what happened without asking you.
A worked example
You have a payroll workbook to email. Open File ▸ Info ▸ Protect Workbook ▸ Encrypt with Password, type a password such as Spr1ng!2026, confirm it, and save. The next time anyone — including you — double-clicks the .xlsx, Excel demands that password before it will display a single cell. Without it the file is unreadable; lose the password and there is no built-in way back in. Encrypt a workbook when the whole document is sensitive — salaries, contracts, personal data — and must not be readable by anyone who gets the file. It is the right tool when the goal is "nobody opens this without the password", as opposed to merely keeping a few formula cells from being overwritten. If there is any chance you will reuse this, drop it into a small template tab right now: a labelled input area on the left and the formula beside it, checked once against the tool above. Next time the same question comes up, the answer is a single paste away instead of a rebuild from memory.
In Google Sheets
Google Sheets handles this almost identically to Excel. The formula syntax above is the same, and the menu lives under a slightly different label rather than a ribbon tab. Use the platform toggle at the top of the page to switch every keyboard shortcut between Windows and Mac, and expect at most cosmetic differences in naming. The aim was to get you unstuck fast and leave you a little more capable than a copy-paste would. The answer is at the top, the tool proves it, and the detail above shows why it holds — so the next time a colleague asks, you can answer without reaching for search. The short version of “password protect a zipped excel file”: the answer is at the top of this page, the tool proves it on your own numbers, and the sections above explain why it holds so the next variation does not stump you. Excel rewards people who reference cells instead of typing values and who keep inputs separate from formulas, because that is what makes a result you can audit months later. Build it once, deliberately, with the live tool as a check, and you convert a one-off lookup into a reusable skill — which is the whole point of learning the why and not just the what.
Common mistakes
- Confusing this with Protect Sheet — encryption controls opening the file, not which cells can be edited.
- Losing the password: encrypted workbooks have no official recovery, so a forgotten password can mean permanent lockout.
- Assuming a read-only or "mark as final" setting is encryption — only Encrypt with Password actually scrambles the file.
- Relying on it for a shared OneDrive file where co-authoring expects an unencrypted document; encryption can block online editing.
Frequently asked questions
Is encrypting the file the same as protecting a sheet?
No. Encryption stops the file from opening without a password; sheet protection (Review ▸ Protect Sheet) lets the file open but locks certain cells from editing.
Can I remove the password later?
Yes — open the file with the password, return to File ▸ Info ▸ Protect Workbook ▸ Encrypt with Password, clear the password box, and save.
What if I forget the password?
There is no official Microsoft bypass for a forgotten open-password; the encryption is genuine, so always store it somewhere safe before you rely on it.