How do I measure my fireplace to purchase an insert?

I would recommend having your local hardware store or fireplaces dealer help you with this step so that they can ensure the measurements are correct before ordering anything online. If you go in by yourself though, Be sure to bring all of the following: (a) The outside dimensions of where your old fireplace was located; (b) Measurements from each opening sidewall down into ground level; (c) Any obstructions within those measurements such as central air vents or window panes directly next to them; (d) Your preferred type of fuel-burning preference (wood, biomass like corn stover), etc.; And (e) What you are trying to accomplish with your fireplace (central heating, supplemental heat source only, etc.).