How to Measure and Size a Drop-In Fire Pit Pan? | The 1-Inch Rule

For the full breakdown, see our best Drop in Fire Pit Pan guide.

Order a pan that matches your fire pit’s stone rim and it will drop straight through the hole. The measurement that decides the fit is the cutout — the opening in the fire pit structure — and matching a pan to it means comparing internal pan dimensions against that opening, not against the outer frame.

Below is the measuring sequence that works, the flange detail almost everyone forgets, and a BTU-to-size chart pulled from real manufacturer listings.

How Do You Measure the Fire Pit Opening?

Measure the inside opening of the fire pit — the actual hole — in both directions, length and width for a rectangular or linear pit, or the full diameter for a round one. The outer stone, tile, or metal frame is irrelevant to whether a pan drops in.

Use a tape measure and take the reading at the narrowest point of the opening. On a round fire pit, measure across the center in two directions and use the smaller number. On a square or rectangular pit, measure both the length and the width of the opening, then record each figure separately.

Once you have the opening dimensions, subtract roughly 1 inch. That result is the pan size you are shopping for.

The 1-Inch Rule and the Flange Nobody Checks

Manufacturers describe the sizing relationship two ways, and they mean the same thing. One version: the pan opening should be about 1 inch smaller than the inside opening of the fire pit. The other, phrased for cutout work: add 1 inch to the pan’s length, width, or diameter to get the required cutout size.

Either way, the point is that the pan’s flange — its lip — seats on the ledge of the opening while the body drops inside it. That lip is bigger than the pan size you order. Listings for stainless drop-in pans show a flange of about 1.25 inches per side on some models, so a pan listed as one size has a larger overall outside footprint once the flange is counted.

This is the most common measuring mistake: comparing a fire pit’s outer dimensions, or a pan’s flange width, against the wrong number. Compare internal pan size to the inside opening, and confirm the flange will land on solid ledge all the way around.

The clearance you leave also absorbs expansion and contraction from heat, which is the stated reason manufacturers call for it rather than a tight zero-gap fit.

Pan Size, BTU Rating, and Compatibility

Pan size determines how much burner and heat output a fire pit can carry, and manufacturers publish BTU ratings tied to specific pan and burner combinations.

Depth is another spec that varies by model, not by brand standard. Several stainless-steel drop-in pans list a depth of 2 inches, but that figure is not uniform across every model on the market.

Other details worth confirming on the exact product page before you buy:

• Gas inlet size. Rectangular models are commonly listed with a 1/2-inch gas inlet, which has to match your supply line and fittings.
• Drainage holes. Some linear drop-in pans ship with built-in drainage so water does not pool around the burner.
• Fuel type. Natural gas and propane versions exist for the same pan sizes, and the burner or ignition system has to match the fuel you are running.
• Ignition style. Model pages list different configurations, including spark-ignition propane and natural gas setups.

If you are weighing a few models side by side before committing, the tested drop-in fire pit pan roundup at Gardening Beyond compares real units so you can check specs against your measurements.

American Fire Products’ buyer’s guide covers the burner, pan, and ignition system matching process in more detail if you want the manufacturer’s full explanation: American Fire Products’ fire pit buyer’s guide.

Typical Pan Sizes and BTU Ratings at a Glance

Use this chart to sanity-check your measured opening against what sellers actually stock before ordering.

Sizes outside those families usually mean a custom or discontinued model.