How to Measure Your Fire Pit for a Cover, Screen or Grate

October 17, 20266 min readErik May

Most people measure the wrong part of the pit, and almost everyone assumes the rules are the same for everything. They aren't. A screen needs to be bigger than your pit. A grate needs to be smaller. Covers depend on which kind of cover you're buying.

Get that backwards and a $400 spark screen shows up that won't sit over the opening, or a grate arrives that won't drop in. So before you order anything, take one measurement properly and write it down.

Take one measurement: the inside diameter

Stretch a tape across the inside opening of the pit, at the widest point, from the inner edge of the wall to the inner edge of the opposite wall.

The two mistakes that cause nearly every wrong order:

Don't measure across the outside of the stone. On a block or paver pit the wall can be four to six inches thick on each side. Measure the outside and you'll be a foot over on a 36 inch pit.

Don't measure the top rim if the opening is narrower. Some pits taper. What matters is the opening you're covering or dropping something into.

For a square or rectangular pit, measure the inside length and the inside width separately. Don't average them.

Write the number down. Everything below works from it.

The rules, in one table

What you're buying	The rule
Spark screen, round (pivot, lift-off, single door)	Inside diameter plus 4 inches
Spark screen, square or rectangular	Inside length plus 4, inside width plus 4
Dome snuffer cover	30 inch fits pits to 28 · 36 inch fits to 34 · 42 inch fits to 40
Folding or one-piece flat cover	4 to 6 inches larger all around than the inside
Fire pit grate, round	At least 6 inches smaller than the inside diameter
Fire pit grate, square	Length minus 6, width minus 6

Notice the direction changes. Anything that sits over the fire gets bigger. Anything that sits in the fire gets smaller.

Spark screens: add four inches

A screen has to rest on the rim, not drop into the opening, so it's sized to overlap. Measure the inside diameter and add four inches.

A 32 inch pit takes a 36 inch screen. A 38 inch pit takes a 42.

One quirk worth knowing on pivot screens: the stated size matches the smaller inside diameter of the frame, and the outer edge sits about an inch wider. That's intentional, and it's why the four inches matters. It's what keeps the screen from sliding in.

For square and rectangular pits, add four inches to the length and four to the width. Screen sizing in that shape is then banded by total perimeter, which is length plus width, doubled. A 30 by 30 inch pit becomes a 34 by 34 inch screen, so a perimeter of 136 inches.

Dome covers and flat covers size differently

This is where people get caught, because both are called covers.

Dome snuffer covers are sold by capacity, not by addition. The 30 inch covers pits up to 28 across. The 36 inch covers up to 34. The 42 inch covers up to 40. Find the band your pit falls into. Don't add anything.

The Legacy Series Fire Pit Snuffer Lid works this way. If your pit measures 32 inches inside, you want the 36. It's covered by our Guaranteed Fit promise, so if the size doesn't fit we'll send the right one and cover the shipping both ways.

Flat covers, folding or one-piece, want four to six inches larger all around than the inside dimensions. These sit flat and seal against weather, so the extra overlap is doing real work keeping rain and snow out of the pit.

If your measurement sits right on a boundary, size up. A cover that overhangs slightly still works. One that's a half-inch short doesn't cover anything.

Grates go the other way

A grate drops inside the pit and needs room for air around it. That clearance is most of why a grate makes a fire burn better.

Round grates: at least six inches smaller than the inside diameter, which leaves about three inches of space all the way around. A 36 inch pit takes a 30 inch grate.

Square grates: take six inches off the length and six off the width.

Our own grates are sized for common pits and listed by diameter:

Walden Original Fire Pit Grate with Ember Catcher, 24 and 29.5 inch, half-inch steel with a built-in ember catcher
Walden Wagon Wheel Steel Fire Pit Grate, 29, 33 and 35 inch
Walden Fire Pit BBQ Grill Grate, 30 and 36 inch, for cooking over the fire rather than just burning in it

So a 36 inch inside-diameter pit wants the 29 or 30; a 42 inch pit wants the 35 or 36.

The whole range lives in Fire Pit Grates, BBQ & Cooking.

If you're between two sizes

It depends which direction the product goes.

Screens and covers: size up. Overhang is fine. A screen that's slightly too small falls in, and a cover that's slightly too small leaves the pit open to weather.

Grates: size down. Clearance is the point. A grate wedged against the walls chokes the airflow you bought it for, and it'll be awkward to lift out when it's full of ash.

Odd shapes, bowls and custom pits

Oval pits, irregular stonework, steel bowls and anything homemade don't fit the table above. Don't guess from the longest measurement. You'll be wrong in one direction and it'll be an expensive wrong.

Send us the measurements along with a photo. Custom sizes are made to order in most of these product lines, and it's a normal request rather than a special favour.

While you've got the tape out

Two things worth noting at the same time, because people usually end up ordering them later anyway.

Pit depth, measured from the rim down to the floor, tells you whether a grate's standard four-inch legs will sit the wood at a sensible height. Shallow pits sometimes want shorter legs.

Rim width, how wide the top edge of the wall is, tells you whether a screen or cover has a flat surface to rest on. Narrow rims and rounded capstones are worth mentioning when you order.

Questions people ask

What size fire pit screen do I need?

Inside diameter plus four inches. A 32 inch pit takes a 36 inch screen. Measure the inside opening, not the outside of the stone.

Do I measure the inside or outside of the fire pit?

Inside, every time, across the opening at its widest point. The outside measurement includes the wall thickness and can be a foot larger on a block pit.

Why is a grate smaller than the pit when a screen is bigger?

A grate sits down inside and needs airflow around it. That's what makes the fire burn hotter and cleaner. A screen rests on top of the rim and needs overlap so it can't fall in.

What size grate for a 36 inch fire pit?

A 30 inch grate. Round grates want at least six inches less than the inside diameter, which leaves roughly three inches of clearance all the way round.

My pit measures between two sizes. Which do I pick?

Size up for screens and covers, size down for grates.

Does the snuffer lid use the same rule as a screen?

No. Dome covers are sold by the pit size they cover rather than by adding inches. The 30 inch covers pits up to 28, the 36 inch up to 34, the 42 inch up to 40.

What if my fire pit is square?

Same logic, measured separately. Add four inches to the length and the width for a screen; subtract six from each for a grate. Square screens are then banded by total perimeter, meaning length plus width, doubled.

Still not sure? Send us your measurements and we'll tell you which size you need. It takes us a minute and it saves you a return.