What is the most common coaster size?

About 4 inches (100 mm) round or square, with 3.5 inch versions also common.

How thick should a laser cut coaster be?

Around 3 to 6 mm. Thin single layers can warp, so many makers stack two layers or add a cork backing.

How many 4 inch coasters fit on a 12 x 20 inch sheet?

About 8 in a simple grid with small gaps, because only two fit across the 12 inch width.

Do wooden coasters need a finish?

Yes. Seal them so they resist water rings and tell customers how to clean them.

Can I cut coasters with a diode laser?

Thin plywood coasters, yes, usually in multiple passes. Clear acrylic needs CO2.

What Size Should a Laser Cut Coaster Be? Inches and mm

A laser cut coaster is a small flat disc or square, usually wood or acrylic, that protects a table from a glass or mug and carries an engraved design. People buy them as gifts, as wedding favours and as housewarming presents, which is why makers cut them by the dozen. The size you choose decides two things: whether the coaster works for real cups, and how many fit on a sheet.

Typical coaster dimensions

Dimension	Common range	Notes
Diameter or side	3.5 to 4 in (89 to 102 mm)	4 in is the common "classic" size
Thickness	1/8 to 1/4 in (3 to 6 mm)	Thin plywood warps; stack two layers or add backing
Corner radius (square)	3 to 10 mm	Rounded corners snag less
Engraving depth	Light	Deep engraving can collect liquid
Set size	4 or 6	Often sold with a holder

A standard drinking glass or mug base is usually smaller than 3.5 inches, so a 3.5 to 4 inch coaster covers most of them. Check the cups your customers use if you cater to large mugs.

How many coasters fit on a sheet

Plywood for lasers is often sold in 12 x 20 inch (305 x 508 mm) pieces. Add a small gap of about 1/8 in (3 mm) between parts so cuts do not overlap.

Coaster size	Across 12 in	Along 20 in	Per sheet (simple grid)
3.5 in (89 mm)	3	5	15
3.75 in (95 mm)	3	5	15
4 in (102 mm)	2	4	8

The cliff is real: at exactly 4 inches, three coasters across need 12.25 inches with gaps, which is more than the 12 inch sheet, so you lose a whole column. Dropping to 3.75 inches nearly doubles the count. If your customers will not notice a quarter inch, the extra coasters pay for themselves. Nesting software can improve odd layouts; see what is nesting.

Material choices

Material	Pros	Cons
3 mm plywood, two layers	Cheap, warm look	Glue between layers adds a step
6 mm plywood	One piece, sturdy	Slower cutting, needs strong laser
Slate	Looks premium, engraves white	Needs a laser that can mark it
Cork backing	Stops sliding, protects table	Extra material
Acrylic	Waterproof	CO2 only for clear acrylic

A basic diode may need more than one pass for 3 mm wood. Read how many passes to cut 6 mm plywood if you plan to cut thicker stock.

Finish matters more than size

Bare plywood absorbs water and leaves rings. Seal both faces and the edges with a clear finish suitable for wood, following the product label, and let it cure fully before use. Coasters touch cups, not food, but the finish label still matters: read it and let the finish cure fully.

Common mistake: Selling bare, unsealed coasters as "waterproof". They are not. Say "sealed" only when you have sealed them, and tell buyers how to care for them.

Worked example

You want 24 coasters for a wedding order at 3.75 in. One 12 x 20 in sheet gives 15, so two sheets give 30, enough for 24 plus 6 spares. If you picked 4 in, 8 per sheet means 3 sheets for the same order. That is a 50 percent difference in plywood for a quarter inch of diameter.

Next step

Cut one test coaster in your usual wood, put a real mug on it, then put your favourite glass on it. If both sit fine, you have your size. Then check the geometric ornament files for patterns you can resize into engraved designs.