How thick a laser cutter can cut depends on the type of laser and the material. A small desktop diode laser tops out around 3 to 6 mm of plywood. A mid-range CO2 laser handles up to about 18 mm of wood or 25 mm of acrylic. Industrial fiber lasers cutting metal go much further, slicing through 40 mm or more of carbon steel at 12 kW, and ultra-high-power systems at 50 kW can cut steel up to 50 mm thick.
Diode Lasers: Desktop Machines
If you’re looking at a hobbyist diode laser in the 10W to 20W range, expect to cut through about 3 mm of plywood in multiple passes. Bumping up to a 40W diode extends that slightly, but most desktop diode lasers max out around 6 mm of plywood. These machines work by making several passes over the same cut line, each one burning a little deeper. Softer woods like poplar cut faster than birch or hardwoods, but the overall thickness limit stays about the same.
Diode lasers are designed for engraving and light cutting. They simply don’t have the power density to push through thicker stock, and adding more passes eventually chars the edges without cutting deeper.
CO2 Lasers: The Workshop Standard
CO2 lasers are the most common type in makerspaces, small businesses, and mid-size fabrication shops. They’re effective on wood, acrylic, leather, fabric, and some plastics. At around 60W (roughly 40% power on a 150W machine), you can cleanly cut 1/8-inch (3 mm) balsa or basswood. At 100W, that jumps to 1/4-inch (6 mm) birch or acrylic. High-power CO2 lasers at 100W and above can cut plywood up to about 18 mm thick.
Acrylic is one of the best materials for CO2 laser cutting because it melts cleanly rather than burning. At higher wattages, cuts through 25 mm acrylic are possible, though edge quality starts to decline. Wood thicker than about 12 mm tends to show more charring on the cut faces, and you’ll notice a wider kerf (the gap left by the cut) as the beam has to melt through more material.
Fiber Lasers: Cutting Metal
Fiber lasers are built for metal. They operate at a wavelength that metals absorb efficiently, making them the go-to for cutting steel, aluminum, brass, and titanium. The thickness they can handle scales directly with power.
- 1 to 2 kW: Reliably cuts 4 to 6 mm carbon steel in production, with an absolute max around 10 mm. Stainless steel tops out around 6 mm, aluminum around 4 mm.
- 3 to 4 kW: Handles 8 to 12 mm carbon steel in steady production, maxing near 20 mm. Stainless reaches about 12 mm, aluminum about 8 mm.
- 6 kW: Production cuts up to 20 mm carbon steel, with a ceiling around 25 mm. Stainless steel goes to 20 mm, aluminum to 12 mm.
- 8 to 12 kW: Cuts 20 to 30 mm carbon steel reliably, pushing to about 40 mm at the extreme. Stainless steel reaches 30 mm, aluminum 18 mm.
There’s an important distinction between “stable production thickness” and “absolute maximum.” The stable range is what a shop can cut all day with clean edges and consistent results. The absolute max is technically possible but produces rougher edges, more slag, and slower speeds. A 3 kW fiber laser can technically push through 20 mm steel, but 12 mm is where you’d want to stay for clean, repeatable work.
Ultra-High-Power Industrial Systems
At the industrial extreme, 50 kW fiber lasers can cut 30 to 50 mm carbon steel using compressed air as the assist gas. Systems at 100 kW are used to cut and weld metal 50 mm and above. These are large-format industrial machines, not something you’d find in a job shop. A more common industrial setup, a 20 kW laser, can cut 20 mm carbon steel cleanly using air assist at full speed.
Titanium is also laser-cuttable but requires careful gas management. Research has demonstrated fiber and CO2 laser cuts through titanium alloy plates up to 30 mm thick, though most practical applications involve sheets in the 1 to 4 mm range.
Why the Same Laser Cuts Different Materials Differently
The maximum thickness isn’t just about power. Three factors determine how deep a laser can cut in a given material: how well the material absorbs the laser’s wavelength, its melting point, and its thermal conductivity. Aluminum, for example, reflects more laser energy and conducts heat away from the cut zone faster than steel, which is why a 6 kW laser cuts 25 mm of carbon steel but only 12 mm of aluminum.
Wood and acrylic absorb CO2 laser wavelengths extremely well, which is why a relatively low-power CO2 laser can cut through thick sheets. Metals barely absorb CO2 wavelengths at all, which is why fiber lasers (with their shorter wavelength) dominate metal cutting.
How Assist Gas Affects Thickness
When cutting metal, a jet of gas blows through the cut to clear molten material. The choice of gas changes how thick you can cut. Oxygen reacts with steel exothermically, adding 60 to 80% more energy to the cut compared to nitrogen or compressed air. This lets you cut thicker material at faster speeds with the same laser power. The tradeoff is that oxygen leaves a thin oxide layer on the cut edge, which can interfere with painting or welding.
Nitrogen produces a clean, oxide-free edge but requires significantly more laser power to achieve the same thickness because the laser alone is doing all the melting. If you need cosmetic or weld-ready edges, you’ll typically sacrifice some maximum thickness capacity to use nitrogen instead of oxygen.
Lens Choice and Thick Material Cuts
The focal length of the lens inside a laser cutter affects the maximum thickness it can handle. A shorter focal length lens (like a 3.75-inch) concentrates the beam into a tighter spot, which is great for thin materials and fine detail. But that tight focus diverges quickly, limiting effective cutting to about 2.5 mm (12-gauge) thickness.
A 5-inch lens extends the effective range to about 6 mm. For thicker stock, a 7.5-inch lens works up to roughly 32 mm, and a 10-inch lens reaches about 33 mm. Longer focal lengths create a wider beam at the focus point, which produces a wider kerf but maintains cutting power deeper into the material. This is necessary for thick cuts because the wider channel gives molten material room to escape.
Edge Quality Drops With Thickness
Regardless of laser type, cutting near the maximum thickness always means compromising on edge quality. The two main issues are taper and surface roughness. Taper means the cut is wider at the top (where the beam enters) than at the bottom. On thin materials this is negligible, but on cuts thicker than about 12 mm, taper becomes visible and may matter for parts that need to fit together precisely.
Surface roughness increases too. One experienced operator noted that half-inch (12.7 mm) steel cuts “butter smooth” on a 3 kW laser, but pushing to 5/8-inch (16 mm) gets noticeably rougher. At a certain point, the beam can’t clear molten metal fast enough, causing recast material (slag) to cling to the bottom edge. This is also why multiple passes don’t work for metal: an incomplete cut sprays molten material upward, damaging the cutting head’s nozzle and optics.
For wood, the equivalent problem is charring. Beyond a certain thickness, the heat exposure time blackens and weakens the cut edges. Slowing down the cut gives the beam more time to penetrate but also more time to burn surrounding material.