Actually, we can find out all locked cells in active worksheet with Find command by following steps:

Step 1: Click Home > Find & Select > Find to open the Find and Replace dialog box. You can also open this Find and Replace dialog box with pressing the Ctrl + F keys.

Step 2: Click the Format button in the Find and Replace dialog box. If you can't view the Format button, please click the Options button firstly.

Step 3: Now you get into the Find Format dialog box, check the Locked option under Protection tab, and click OK.

Step 4: Then back to the Find and Replace dialog box, click the Find All button. Now all locked cells are found and listed at the bottom of this dialog box. You can select all searching results with holding the Ctrl key or Shift key, or pressing the Ctrl + A keys.

If you check the Select locked cells option when you Lock and protect selected cells, it will select all locked cells in active worksheet, and vice versa.

Kutools for Excel's Select Cells with Format utility can help you quickly select all locked cells in a certain range. You can do as follows:

1. Select the range in which you will select all locked cells, and click the Kutools > Select > Select Cells with Format.

2. In the opening Select cells with Format dialog box, you need to:

Then you will see all locked cells in the selected range are selected as below screen shot shown:

Actually, Kutools for Excel provide another Highlight Unlocked utility to highlight all unlocked cells in the whole workbook. By this utility, we can identify all locked cells at a glance.

Click the Kutools Plus > Worksheet Design to enable the Design tab, and then click the Highlight Unlocked button on the Design tab. See below screen shot:

Now you will see all unlocked cells are filled by color. All cells without this fill color are locked cells.

Note: Once you locked an unlocked cell in current workbook, the fill color will be removed automatically.