Example using default google maps embed code, with the 100% width tip.

Open Google Maps - https://www.google.com/maps

Type in desired location into google

Click on Gear Icon on bottom right of map display

Pop up menu will appear, click Share or embed map

On Embed map tab, copy link. Can change the size of image on left side of link area. It can be made to custom size.

Once copied, look for Copy and paste into textarea for Map Embed Code Textarea.

Scroll up to top, and click Update Page.

Example using shortcode provided by Jetpack

Visit Google Maps - https://www.google.com/maps

Type, or paste address - Click search button

After map is loaded, click on Gear Icon that is located in the lower right corner of browser window.

Select Share and embed map.

Select the Embed map tab and copy the code from the box. The code begins with <iframe.

Posting code

Post code in this box