Should I scale by percent or by size in millimetres?

By millimetres. Type the exact target width or height with proportions locked. It is easier to check and avoids cumulative rounding.

How does scaling affect cutting time?

Cut length scales with the factor, so cut time grows about in proportion. Engraving time grows with the area, which is the factor squared.

Why do my scaled holes look wrong?

Holes scale with the file. A 4 mm hole at 200% becomes 8 mm. Redraw holes and slots to the size the material and cord need.

Can I scale a box file to make it larger?

Not safely. Joints depend on material thickness and kerf. Regenerate the box with new inside dimensions instead.

Does scaling change stroke width?

It can. In Inkscape, turn off Scale stroke width for laser files so hairlines stay hairlines.

How to Scale Laser Files Without Breaking Them

The reindeer is perfect at 90 mm. Then a customer asks for a big one for the front door, so you drag the corner handle until it looks about right and press Start. The cut goes fine, but the 4 mm hanging hole is now 11 mm, the thin antlers are thick as bananas, and the engraving takes four times as long. Scaling laser files looks like one drag of the mouse, but a few things quietly change with it.

This guide shows how to scale without surprises.

The golden rules of scaling

Always lock proportions (aspect ratio) unless you want a deliberately distorted shape.
Type the target size; do not eyeball it.
Scale before you add details that should keep a fixed size, such as hanging holes or kerf compensation.
Re-test on scrap after any size change of more than about 20%.

Work out the scale factor

Scale factor = target size ÷ current size. Use the same dimension for both, such as width, measured in millimetres.

Current width	Target width	Factor	Percent
90 mm	135 mm	1.5	150%
90 mm	60 mm	0.667	66.7%
124 mm (height)	200 mm	1.613	161.3%
100 mm	75 mm	0.75	75%

Notice the third row: choose the dimension that matters for your sheet. A reindeer that must fit a 200 mm tall frame is scaled by height, and the width follows.

What changes when you scale

Not everything scales the same way, and that matters for time and material.

Property	Behaviour	Example (reindeer 90 × 124 mm, 0.47 m cut)
Cut length	Scales with the factor	150% gives about 0.71 m
Cut time	About proportional to cut length	40 W CO2: 44 s becomes about 66 s
Engraved area	Scales with the factor squared	150% gives 2.25 times the area
Engrave time	About proportional to area	Plan for more than double
Parts per sheet	Falls fast	300 × 400 mm: 9 at 100%, far fewer at 150%
Hole size	Scales with the factor	4 mm hole becomes 6 mm
Stroke width	Depends on your software setting	See below

Note on the parts per sheet: the 9 per 300 × 400 mm and 18 per 600 × 400 mm figures are a simple grid at 100% size. At 150% the part is about 135 × 186 mm, so only about two columns by two rows fit in the smaller sheet. Bigger parts also mean more offcut waste, so see what is nesting.

Scaling in Inkscape

Select the group and open the Transform dialog (Shift+Ctrl+M), Scale tab. Choose mm, tick Scale proportionally, and enter the new width. Or use the toolbar W and H fields with the lock icon engaged.

The stroke setting is the trap. In the toolbar, there are four toggles: scale stroke width, scale rounded corners, move gradients, move patterns. For laser files with hairline strokes, switch off Scale stroke width so a 0.1 mm hairline stays 0.1 mm instead of becoming 0.15 mm or 0.067 mm. Most laser software ignores stroke width anyway, but a consistent hairline keeps the preview readable.

Scaling in LightBurn

Select the shape, open the Size section in the toolbar, make sure the padlock is closed (proportional), and type the width or height. You can also use Edit > Scale for percent values. Remember that LightBurn scales the geometry only; the layer settings, like speed and power, do not change. A large piece may need a slower speed pass in a different spot or longer air assist time.

Fix the features that should not scale

Some details are about the material, not the design.

Feature	Depends on	Do this after scaling
Hanging hole	Cord or ribbon width	Reset to 3–5 mm. See hanging hole size
Slots and tabs	Material thickness	Redraw to match the sheet (3 mm slot for 3 mm ply, minus kerf)
Thin necks and tips	Strength of the wood	Keep 2 mm or more across in 3 mm plywood
Text height	Readability	Keep 4 to 5 mm or more for engraving
Kerf compensation	Machine and material	Does not scale; apply per job

Common mistake: scaling a finger-joint box to "make it a bit bigger". The tab length and slot width are tied to the plywood thickness and the kerf, so after scaling the joints no longer fit. Open the box generator, type new inside dimensions and download a fresh SVG or DXF.

When your scaled file arrives at the wrong size

Sometimes the file is not at the size you set. This is a separate problem: the file's own units are being interpreted differently (72, 90 or 96 pixels per inch). The factors are 133.3% (96 over 72), 106.7% (96 over 90) and 75% (72 over 96). The details are in why an SVG is the wrong size in LightBurn. After correcting, you can scale for your project.

Pro tip: put a 50 mm square in the file before you scale and scale it along with the design. After scaling, the square shows exactly the factor you applied. Delete it before the cut.

A worked example

Goal: a 300 mm tall door reindeer from our reindeer file, which is 90 × 124 mm.

Factor = 300 ÷ 124 = 2.419.
New width = 90 × 2.419 = 217.7 mm. New cut length = 0.47 × 2.419 = about 1.14 m.
The hole: 4 × 2.419 = 9.7 mm. A door hook wants 8 to 10 mm, so keep it.
Antler tips scale from roughly 2 mm to 4.8 mm, which is actually stronger, so no fix.
Plywood: 3 mm ply at this size will flex. Switch to 6 mm and expect two to three passes on a diode laser or slower speed on CO2. Read passes to cut 6 mm plywood.

Scale down: the hidden risk

Going small is harder than going big. Reducing to 50% puts a 2 mm neck at 1 mm, below what 3 mm plywood can support, and the beam width starts to erase detail. Halve a design only if you can adjust the thin parts.

Scaling checklist for a batch

Question	If yes	If no
Is the target size typed in millimetres?	Continue	Type it, do not drag
Are proportions locked?	Continue	Lock them
Do holes and slots still fit the cord or sheet?	Continue	Redraw them
Is the thinnest feature 2 mm or more in 3 mm ply?	Continue	Thicken or change material
Did you recompute cut time and sheet count?	Continue	Check your price

Pricing follows the same rule. If your ornament sells at one size and you offer a bigger one, the material and time grow faster than the width, so do not simply add 50 percent to the price for a 50 percent larger piece. Compare the time estimate in the laser software for both and price from there.

Next step

Pick an ornament, choose a target size, calculate the factor, scale proportionally, then fix the hole and thin parts using the tables above. Cut one on scrap before committing to a full sheet.