Surface smoothness on curved 3D prints is governed by trigonometric layer-step math. This tool calculates the effective vertical resolution and facet angles based on your layer height and printer nozzle or LCD panel specs. Step riser, step tread, worst-case faceting at 45°, sanding estimates, print-time tradeoffs, and the maximum unsupported overhang for seven materials. Runs entirely in your browser — no uploads, no accounts, no cookies.
Features
Layer count from model height
Step riser, tread, and facet geometry
Worst-case faceting at 45° surfaces
Sanding effort estimate per layer height
Max unsupported overhang for 7 materials
MSLA LCD pixel pitch for resin XY detail
Calculator
Process:
Your slicer's layer height. Halving it halves every step on the model.
mm
Eye level to base — 32mm for a heroic-scale figure, 40mm for a bust or 40mm model.
Layer height presets:
°
0° is a flat ceiling, 90° is a vertical wall. Curved surfaces pass through every angle, and 45° is where the faceting is worst.
PLA supports up to 55° from horizontal
Common angles:
MSLA Panel — the XY limit on resin
Pixel pitch: 0.0463 mm — resin looks smooth in XY because this is finer than your layer height
Layer Count
200
~1.0× print time
Step Riser (Z)
0.200
mm vertical
Step Tread (XY)
0.200
mm horizontal run
Step Facet
0.283
mm chunk on the surface
Worst Facet on Model
0.283
mm — the 45° chunk on a curve
Sanding Estimate
0.100
mm average to fair
Visibility
Visible
above the 0.1mm eye threshold
Support needed
The math
40 ÷ 0.200 = 200 layers · tread = 0.200 ÷ tan 45° = 0.200 mm · facet = 0.200 ÷ sin 45° = 0.283 mm
Geometry is only half of the surface quality
These numbers describe the staircase the slicer cuts. They say nothing about the ridges and valleys your extruder leaves on top of each step, which is why a 0.08mm layer height on FDM still needs sanding to clear a visible seam. That texture scales with nozzle diameter, not layer height. On resin, the same stair-stepping applies in Z while the XY surface is limited by the LCD pixel instead — the panel figure is why a 0.05mm resin print looks glassy on a curve where 0.05mm FDM still looks layered.
Every layer adds one step of exactly your layer height. That vertical riser is constant no matter which way the surface faces, so a 0.2mm print has 0.2mm of stair-stepping in Z. What changes with the surface angle is the horizontal run: the tread is layer height ÷ tan(angle from horizontal), which is why a vertical wall comes out geometrically flat while a 45° curve is where the faceting is worst. On a curve, the chunk you actually feel is layer height ÷ sin(angle), peaking at 45° at 1.41× the layer height.
Layer count is linear in the inverse of layer height, not exponential. Dropping from 0.2mm to 0.08mm gives you 2.5× the layers and 2.5× the fineness — a 60% cut in step size for 2.5× the layer count. That is the whole trade: sand for two hours, or wait for five times as many layers.
Layer Height Compared
A 40mm tall model, faceting at its worst 45° point. Step size is what your hands feel; the sanding figure is the average material to fair it off.
Layer
Layers
Worst facet
Sanding
Print time
0.280mm
143
0.396mm
0.140mm
~0.78×
0.200mm
200
0.283mm
0.100mm
~1.00×
0.160mm
250
0.226mm
0.080mm
~1.22×
0.120mm
334
0.170mm
0.060mm
~1.55×
0.080mm
500
0.113mm
0.040mm
~2.05×
0.060mm
667
0.085mm
0.030mm
~2.55×
0.100mm
400
0.141mm
0.050mm
~1.00×
0.050mm
800
0.071mm
0.025mm
~1.45×
0.030mm
1334
0.042mm
0.015mm
~1.95×
0.020mm
2000
0.028mm
0.010mm
~2.40×
0.015mm
2667
0.021mm
0.007mm
~2.90×
Print time is a rough baseline against 0.20mm FDM and 0.10mm resin, not a slicer estimate. It grows more slowly than layer count because thin layers are lighter per layer, but the Z travel, acceleration, and per-layer overhead do not shrink. Anything that is not full of 45° curves does not need the bottom of this table.
Maximum Unsupported Overhangs
Material
Max angle
Notes
PLA
55°
Best overhangs of the common filaments
PETG
50°
Stringy at the limit — plan supports early
ABS / ASA
55°
Rigid, grips the bed well
TPU (95A)
40°
Sticky — the worst overhangs of any material
Nylon (PA12)
50°
Warps unless dried and enclosed
Polycarbonate (PC)
55°
Needs 280°C and an enclosure
Resin (MSLA/SLA)
90°
No overhang limit — needs drainage holes instead
Angles are measured from the build plate, so a bigger number is a steeper wall. The classic 45° rule is the FDM average of this column — anything past it starts drooping into the layer below. Resin has no limit at all; a flat ceiling on resin needs drainage holes, not support.
How to pick a layer height
1
Start at 0.20mm and go down only if you must
0.20mm is the right answer for most FDM miniatures. Halving to 0.10mm buys you 0.1mm of step size and costs double the layers, and a well-primed 0.20mm print under a good light hides the difference on anything but a sphere or a hooded cloak.
2
Spend the resolution where the 45° angles are
Run the calculator at 45° to see your worst case, then look at the model. If the stepping you dislike is on a cape hem or a shoulder pauldron, a thinner layer helps. If it is on flat armour plates, no layer height will fix it — you are looking at extrusion ridges, and the nozzle diameter is the dial that matters.
3
Resin lives at 0.05mm, not 0.02mm
Going from 0.05mm to 0.02mm on resin buys 0.03mm of Z resolution and costs 2.5× the exposure count, most of which is light bleeding between layers on anything but a fresh vat. The bigger resin win is XY: your LCD panel is usually finer than your layer height, so a 0.05mm print already resolves detail below what your eye picks out on a curve.
4
Check the angle before you trust the overhang
Set the calculator to the steepest part of your model and read the overhang box. Under 45° on FDM you are fine; past it, the layer sags into the one below and the fault shows up on a cape or a beard as a wave that no amount of sanding will fix. Reorient the model if you can — rotating a part 90° turns its worst overhang into its best.
Layer Height & Angle FAQ
What layer height should I print a miniature at?
0.20mm for most FDM miniatures. Halving it to 0.10mm halves the step size and doubles the layer count, and on anything that is not a sphere or a hooded cloak the difference disappears under primer. Spend the resolution on the model features that actually show stepping, not evenly across every print.
Does halving the layer height halve the stair-stepping?
Yes, exactly. Every layer contributes one step of precisely your layer height, so 0.2mm steps are 0.2mm and 0.1mm steps are 0.1mm. The step size scales linearly with layer height in every direction, which is why the faceting number in the calculator moves with it rather than staying stubbornly proportional.
What is the 45° overhang rule?
On FDM, surfaces steeper than about 45° from the build plate need support. The extruded layer has no support structure underneath it to hold it to the plate, so past 45° the plastic droops into the layer below and cures in the wrong shape. The real limit moves with material — PLA manages 55°, TPU gives up around 40° — and with nozzle size, since a wider nozzle bridges the gap better.
Why does resin need drainage holes instead of support?
Because liquid resin is held up by the build platform, not by anything extruded below it. Every angle prints unsupported at full quality, including a completely flat ceiling. What that ceiling needs is somewhere for uncured resin to go — two 2mm holes let it drain instead of pooling and curing into a bump you have to sand off.
Does a thinner layer height make prints look better?
It makes them look smoother, which is different. Thinner layers fix geometric stair-stepping, but the ridges and valleys your extruder leaves on top of every step come from nozzle diameter and flow, not layer height. A 0.08mm print with a 0.4mm nozzle still needs sanding to clear the seam line, which is why the calculator warns that geometry is only half of surface quality.
Is 0.02mm layer height worth it on resin?
Rarely. Going from 0.05mm to 0.02mm buys 0.03mm of Z resolution and costs 2.5× the exposure count, most of which is light bleeding between layers on anything but a fresh vat. The bigger resin win is in XY, where your LCD panel is usually finer than your layer height — which is why 0.05mm resin already looks glassy on a curve where 0.05mm FDM still looks visibly layered.
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