How do you easily add equation numbers to Microsoft Word 2010 equations?

You can create a template that can be used to automatically generate the table and equation with number to the right:

1. Insert → Table → 3x1.

2. Right click table → Table Properties.

3. In Table Tab, Check Preferred Width → Percent → 100.

4. In Column Tab, set preferred width to 7%, 86% and 7% for 1st 2nd and 3rd column respectively.

   These values work well for Times New Roman 12pt equation numbers. (Other percentages will work provided they add up to 100%.)

5. Click Ok.

6. Insert → Equation into center column (type in current equation or placeholder).

7. Click References → Insert Caption.

   Select Label: Equation
   Position: Above or Below

8. Adjust numbering as desired.

9. Cut and past number from above location to right column of equation table.

10. Right-align text in right column.

11. Center equation column.

12. Highlight the entire table.

13. Turn off borders.

14. Re-highlight the entire table.

15. Select Insert → Equation → Save Selection to Equation Gallery.

Now if you want to insert an equation with automatic numbering in standard journal/conference paper format, just select the template you have made from the equation gallery and it will insert it into the document as desired.

Equation numbers will be automatically updated and references can be made to them using the References → Cross Reference option for equations.

NOTE: If you'd like to save this newly formatted equation as a keyboard shortcut (like pressing the Alt and + keys simultaneously in order to create a new equation), you can do so by going to File → Options → Customize Ribbon → Customize Shortcuts and then selecting "Building Blocks". Search for your newly created equation template in the right list, then assign a keyboard shortcut to it.

Although the OP asked about Microsoft Word 2010, there is another option in Microsoft Word 2016 that seems to work better. Based on this MSDN blog post, it is now possible to insert right-aligned equation numbers natively within the equation block. With this solution, there is no need for a table or style separators.

1. Insert empty display equation with Insert->Equation
2. Type equation (or placeholder)
3. Still within the equation, type #(1) followed by Enter to format the equation. This should result in a centered equation and right-aligned figure number.

For manual equation numbering you could stop here. To set up automatic numbers, you would continue with a similar procedure to the original solution:

4. Click References → Insert Caption. Select Label: equation, and check "Exclude label from caption" (depending on your formatting preference).
5. Cut and paste the new caption into the equation block, replacing the manual "1" number.

At this point, you can save the entire captioned equation with Design → Equation → Save Selection to Equation Gallery.

To reference the automatic equation number inline, you would create a bookmark and reference the bookmark:

1. Highlight the automatic equation number inside the equation block, and click Insert → Bookmark. You can include the parentheses in the bookmark text, or just highlight the number itself.
2. Add a new named bookmark
3. With the cursor in the text where you want the equation reference, click Insert → Cross-reference, select reference type "Bookmark" and select your new bookmark.

This is a perennial question so I hope you will not mind me submitting another answer.

The problem with the "table" approach is that it breaks the paragraph. This can cause spacing issues if your equation is part of a continuous sentence and your paragraphs have spacing before or after them. It also means that wrapping is done rather poorly for long equations (the usual preference in journals is that, if the equation is the width of the column, the number should appear below the equation right aligned instead of breaking the equation). Finally it does nothing to solve the problem that you wish to have punctuation marks instantly after your Display equation in the normal paragraph font.

My solution is to insert a style separator instantly after the equation. On Windows, use Ctrl-Alt-Enter to insert a style separator. (On a Mac this is not available, but if you open a document created in the Windows version of Word you can copy the style separator into Mac). Then you may insert a tab (with a final right-aligned tab stop already created) and the appropriate equation number autotext. After the equation number you should insert a full paragraph break and not a line break, but at least in Word 2012 the paragraph break is treated as though it were a line break for layout purposes. This may be a bug.

If you want your equations neatly aligned at the equals sign, this is, to my knowledge not possible using this work-around. One way around this is to write your punctuation inside the equations, inside double quotation marks. The Equation tool converts this into free form text which may be placed in whichever font you prefer. I also use this method when I want several small display equations on one line separated by commas or the expression ", and ". However, you cannot number these equations, or at least you can only number the final equation in the set.

The result, with hidden paragraph marks on, looks something like this.

[Note I have also changed the default behaviour of line breaks in fully justified text so that the final line before the line break is not fully justified.]

The style separators here are the thin dotted lines at the end of equations (2.27)–(2.29). Mac Word does not have the proper glyphs to display style separators with a proper picture as you would find in Word for Windows.

Inserting a line break instead of a paragraph break after the equation number seems to cause buggy layout behaviour on my machine.

Unfortunately the end of the sentence after your equation, on the new line, looks as though it is a fresh sentence to the spelling and grammar checker, probably because of the paragraph mark. I have accepted this and resorted to using "ignore" very frequently.

There is a final caveat: when referring to the equations later, the tab before the equation seems to show up with the reference number. You can avoid this by giving an explicit field switch of the form \#(0.0x);(0.0x).

I have been using this approach in a document I am writing which is now up to 160 pages containing a few hundred equations so I think it is relatively robust, once you get it to work.