Two costs with opposite shapes
Every resin print carries two kinds of cost, and confusing them is what makes people price small parts badly.
The first is the resin, which is strictly proportional to the volume of cured material — part plus supports plus whatever you lose to drips and vat residue. Print twice the volume and you pay twice as much. Nest twice as many copies on the plate and the resin cost per part does not change at all.
The second is everything else: the isopropyl alcohol or wash water you consume, the FEP film that wears out every few dozen prints, the LCD screen that has a rated life in hours, the electricity, and whatever you charge for the machine's time. All of that is charged per plate, not per part, and it divides by however many parts you nested.
This is where MSLA differs fundamentally from filament printing. An FDM machine traces every part with a nozzle, so ten copies take ten times as long. An MSLA machine exposes an entire layer at once through an LCD mask, so a plate of forty miniatures takes exactly as long as one miniature of the same height. Nesting is free in time and it divides all the fixed costs. On the default numbers here, going from 8 parts per plate to 32 drops the fixed share per part from $0.3375 to $0.0844 and cuts the total cost per good part from $0.99 to $0.73.
The failure allowance sits on top of both. Everything you spend on a part that fails has to be recovered from the parts that succeed, so the cost of a good part is the nominal cost divided by the yield.
Working through the terms
Volume, including supports. Your slicer reports the volume it will actually cure, which is what you want. Supports on a well-oriented mechanical part might be 10% of the model; on a miniature raised on a raft with dense contact points they routinely reach 25 to 50%. Both go in.
Waste. Resin leaves the bottle and does not all end up in a part. A film clings to every surface and drips into the wash, the vat filter catches a skin of partly cured material, and every vat change loses a little. Five to twelve percent covers ordinary practice; filtering the vat back into the bottle after each few plates is what keeps it at the low end.
Price and density. Resin is sold by volume, in litres, but it is often discussed by weight. The bridge is the density, which for standard photopolymers sits near 1.10 g/mL — so a 1 L bottle contains about 1,100 g. If a supplier quotes a price per kilogram, divide by 1.1 to get the price per litre before comparing.
Fixed costs per plate. Work out each one as a total cost divided by a life. A $12 FEP that survives 40 plates is $0.30 a plate. A $60 monochrome LCD rated for 2,000 hours, on 4-hour plates, is 4 × 60 ÷ 2,000 = $0.12. A 4 L jug of IPA at $20 that washes 15 plates before it is too saturated to work is $1.33. Add them, put the total in, and the calculator divides by your parts per plate.
Failure rate. Dividing by (1 − f) rather than multiplying by (1 + f) is the correct treatment, and the difference grows fast. At 5% failures the multiplier is 1.053; at 25% it is 1.333; at 50% it is exactly 2.
Setting the two cost terms equal gives you a useful crossover: V* = 1000·F / (n·(1+w)·P). On the defaults that is 2.70 × 1000 ÷ (8 × 1.08 × 35) = 2,700 ÷ 302.4 = 8.93 mL. Below that part volume the fixed costs are the bigger half of the bill; above it the resin is.
Worked example: eight 12 mL parts on a plate
You are printing eight copies of a 12 mL part, each carrying 4 mL of supports, on a plate that takes about four hours. Resin is $35 a litre at 1.10 g/mL, you allow 8% waste, your wash costs $1.50 a plate, film and screen work out to $0.60, machine and power to $0.60, and about one part in twenty fails.
- Volume per part. 12 + 4 = 16 mL.
- With waste. 16 × 1.08 = 17.28 mL of resin leaves the bottle per part.
- By weight. 17.28 × 1.10 = 19.01 g.
- Resin cost per part. 17.28 ÷ 1000 × $35 = $0.6048.
- Fixed cost per plate. 1.50 + 0.60 + 0.60 = $2.70.
- Fixed cost per part. 2.70 ÷ 8 = $0.3375.
- Cost before failures. 0.6048 + 0.3375 = $0.9423.
- Cost per good part. 0.9423 ÷ 0.95 = $0.9919.
- Cost of the whole plate. 8 × 0.6048 + 2.70 = 4.8384 + 2.70 = $7.54.
- Parts per litre. 1000 ÷ 17.28 = 57.9.
Now nest 32 instead of 8, which on most plates simply means using the area you were leaving empty. Resin cost per part is unchanged at $0.6048, but the fixed share falls to 2.70 ÷ 32 = $0.0844, so the cost per good part becomes (0.6048 + 0.0844) ÷ 0.95 = $0.7254 — a 27% reduction from a change that costs nothing in print time.
Resin cost per part by volume and resin price
| Part + support volume (mL) | Resin used (mL) | at $25/L | at $35/L | at $60/L | at $120/L |
|---|---|---|---|---|---|
| 2 | 2.16 | $0.054 | $0.076 | $0.130 | $0.259 |
| 5 | 5.40 | $0.135 | $0.189 | $0.324 | $0.648 |
| 10 | 10.80 | $0.270 | $0.378 | $0.648 | $1.296 |
| 16 | 17.28 | $0.432 | $0.605 | $1.037 | $2.074 |
| 25 | 27.00 | $0.675 | $0.945 | $1.620 | $3.240 |
| 50 | 54.00 | $1.350 | $1.890 | $3.240 | $6.480 |
| 100 | 108.00 | $2.700 | $3.780 | $6.480 | $12.960 |
| 250 | 270.00 | $6.750 | $9.450 | $16.200 | $32.400 |
As a working guide, a 32 mm tabletop figure with supports usually slices somewhere between 2 and 5 mL, and a 75 mm display bust between 40 and 90 mL — but slice your own model rather than trusting a range, because hollowing changes it by a factor of three or more.
What to do with the number
Look first at the split between the two components in the results table. If the resin share is small, your lever is nesting: fill the plate. If the resin share is large, your levers are hollowing the model, reducing support volume, and buying resin in larger bottles.
Hollowing is the biggest single saving available on display pieces. A solid 80 mL bust hollowed to a 2 mm wall with drain holes can drop below 30 mL, cutting the resin bill by more than half. It also prints better, because a solid mass of resin generates heat as it cures and shrinks unevenly. What it costs you is the need for drainage holes, and a part that is lighter in the hand.
Support volume is the quietly expensive one. Auto-generated supports at default density on a miniature can approach the volume of the model itself. Reducing the raft thickness, raising the part less far off the plate and thinning the support struts all pay directly.
For pricing rather than costing, this number is your floor, not your price. It excludes post-processing labour — washing, support removal, curing, sanding, priming — which on a miniature is usually worth more than everything on this page put together. It also excludes the fraction of a bottle that goes off before you use it, which is real if you print rarely.
If you are comparing the two technologies for a job, run the same part through the FDM print cost calculator and remember the structural difference: on FDM, ten copies cost ten times the machine time, so the fixed costs do not divide the way they do here. Use the print time estimator to see what that machine time would be.
Costs this page does not include
- Post-processing labour. Washing, support removal, curing, sanding and priming are usually the largest real cost of a finished resin part, and none of it is here.
- Contaminated alcohol disposal. Uncured resin is an aquatic toxicant and waste IPA cannot go down a drain. In a commercial setting, disposal is a line item; at home, cure the residue in sunlight before binning it.
- Resin that goes off unused. Photopolymer degrades with light and age. A hobbyist who buys a litre and uses 300 mL over a year has an effective price per millilitre far above the sticker.
- Personal protective equipment beyond gloves. Respirator cartridges and ventilation both cost money.
- The printer itself. Amortise the machine into the machine-cost-per-plate field if you want it counted: a $300 printer over 500 plates is $0.60 a plate on its own.
- Rejects found after post-processing. The failure rate here is applied to the whole per-part cost, which is right for a print that fails on the plate but understates one you discover is bad after an hour of finishing work.
Millilitres, grams and cubic centimetres
One millilitre is exactly one cubic centimetre, so a slicer reporting 17.28 cm³ and one reporting 17.28 mL are saying the same thing. Grams are different: 17.28 mL of standard resin at 1.10 g/mL weighs 19.01 g, so a figure quoted in grams is about 10% larger numerically than the same quantity in millilitres. When comparing supplier prices, convert everything to dollars per litre — a resin at $38 per kilogram is $41.80 per litre at 1.10 g/mL, which is more expensive than it first appears.
Key terms
- MSLA
- Masked stereolithography — an LCD panel masks a UV array so an entire layer cures at once. Print time depends on the number of layers and the exposure per layer, not on how much resin the layer contains.
- FEP
- The transparent fluoropolymer film in the bottom of the vat that the cured layer peels away from. It clouds and stretches with use and is replaced every few dozen prints.
- Vat residue
- Resin left clinging to parts, the vat walls and the filter. It is the main source of the waste percentage.
- Hollowing
- Replacing the solid interior of a model with a thin shell and drain holes. It is the largest single reduction available in resin consumption on a display piece.
- Yield
- The share of attempted parts that come out usable. Cost per good part is the nominal cost divided by the yield.
How resin economics differ from everything else in the shop
Casting and moulding sit next door to resin printing and behave the same way arithmetically, because they too are volume-priced materials poured into a fixed geometry. If you are printing a master to cast from, the silicone mould material calculator gives the volume of rubber the mould needs and the resin mould volume calculator gives the pour, and the same discipline applies: measure the actual displaced volume rather than estimating from outside dimensions. Surface coating is a different geometry again, priced per unit area rather than volume, which the epoxy coverage calculator handles.
What makes MSLA unusual is the flatness of its time cost. Because a whole layer cures at once, the marginal print time of an extra part nested beside an existing one is zero — the only limit is plate area and the fact that a taller part sets the layer count for everything on the plate. That is why production resin shops obsess about nesting density in a way that filament shops do not, and why the parts-per-plate field on this page moves the answer more than any other input except part volume.
The other unusual feature is consumable wear that is charged in hours rather than in parts. An LCD screen has a rated life measured in exposure hours, so a shop running short, dense plates burns screen life much more slowly per part than one running tall single models. Working out that cost properly means dividing the screen price by its rated hours and multiplying by the hours a plate takes, rather than guessing a per-print figure — the same discipline the machine-cost field asks for.