Ink usage is volume times density, and nothing else
A print run consumes a slab of ink: the inked area multiplied by how thick the screen lays it down. Weigh that slab and you have your ink usage. Everything printers argue about — mesh count, squeegee durometer, off-contact, stroke angle — matters only because it changes one number in that product, the film thickness.
Working it this way rather than from a remembered rule of thumb has a practical advantage: the rules of thumb are all expressed as yields, and a yield already contains an assumed thickness and density. If you print a heavy white on a coarse mesh and then reuse a yield figure that came from a fine-mesh black, you can be out by a factor of three. Deriving the yield from your own deposit and your own ink's density keeps the assumption visible.
Coverage is the other number you must own. A print's bounding box is easy to measure and almost always overstates the ink, because most designs are largely open. Multiplying the box by an honest coverage fraction is the difference between a usable estimate and a wild one.
Turning grams per cubic centimetre into square inches per ounce
Start with the volume. Inked area in square inches times film thickness in inches gives cubic inches of ink. A 11 × 11 in print at 60% coverage is 72.6 in² of ink; at a 1.2 mil deposit — 0.0012 in — that is 0.08712 in³.
Then the density. Data sheets give ink density in grams per cubic centimetre, or as specific gravity, which is the same number. One cubic inch is 16.387064 cm³ and one ounce is 28.349523 g, so the conversion factor is 16.387064 ÷ 28.349523 = 0.5780375 ounces per cubic inch for every 1 g/cm³ of density. A plastisol at 1.25 g/cm³ therefore weighs 1.25 × 0.5780375 = 0.7225 oz per cubic inch, and our 0.08712 in³ of ink weighs 0.06295 oz.
Yield falls out of the same two numbers. One ounce of ink is 1 ÷ 0.7225 = 1.384 in³, and spread at 0.0012 in thick it covers 1.384 ÷ 0.0012 = 1,153 in². That is what "1,153 square inches per ounce" means, and it is why the shop rules of thumb — roughly 1,200 in²/oz off a 110 mesh, roughly 2,500 in²/oz off a 305 — are consistent with deposits of about 1.2 mil and 0.55 mil respectively. The rule of thumb is the physics with the thickness hidden inside it.
Colours multiply. Each colour is its own screen and its own pass, so a three-colour design lays down three slabs. If one of them is a white underbase under a light ink on a dark garment, count it: an underbase is usually the heaviest deposit in the whole job, and printers who forget it under-order by a third or more.
Worked example: 500 shirts, one colour, 11 × 11 in at 60% coverage
You have 500 shirts with a single-colour front print in an 11 × 11 in area. Looking at the film, about 60% of that box carries ink. Your 110 mesh with a 70-durometer squeegee lays down about 1.2 mil, and the plastisol's data sheet gives a density of 1.25 g/cm³ at $5.00 per pound.
- Bounding box. 11 × 11 = 121 in².
- Inked area. 121 × 0.60 = 72.6 in² per print.
- Density in imperial units. 1.25 × 0.5780375 = 0.72255 oz/in³.
- Yield. 1 ÷ (0.0012 × 0.72255) = 1,153 in² per ounce.
- Ink per print. 72.6 ÷ 1,153 = 0.06295 oz, which is about 1.8 g.
- Whole run. 0.06295 × 500 × 1 colour = 31.47 oz, or 31.47 ÷ 16 = 1.967 lb.
- Prints per pound. 16 ÷ 0.06295 = 254 prints.
- Gallons. At 1.25 g/cm³ a gallon weighs 1.25 × 8.3454 = 10.43 lb, so 1.967 ÷ 10.43 = 0.19 gal — a quart is plenty.
- Cost. 1.967 lb × $5.00 = $9.84 for the run, or $0.0197 per shirt.
Two pence of ink per shirt is the usual shock in this calculation, and it is real: ink is rarely the expensive part of screen printing. The screens, the film, the setup and the labour are, which is why the crossover against vinyl in the HTV usage calculator happens at such low quantities. Price the job with the screen print pricing calculator, not from the ink.
Reading the yield, and what it does not include
The yield figure is the most portable number on the page. Once you know your press and mesh deliver about 1,150 in² per ounce, you can estimate any job in your head: divide the inked area by 1,150 to get ounces per print. Measure it once by weighing a container before and after a known run, and you will have a shop-specific number better than any published one.
Prints per pound is the same information in the form purchasing wants. It moves inversely with both coverage and deposit: doubling either halves it. That is the whole reason mesh selection is an economic decision as well as a quality one.
What this number is not is the ink you will consume. It counts only ink that lands on garments. Real consumption also includes the flood that sits in the screen at the end of the run, the film left on the squeegee and the flood bar, what is scooped back into the container with a card and what is not, and the ink lost when a screen is washed out. On a 500-piece run those losses are a modest fraction. On a 24-piece run they can exceed the print itself, which is why short runs feel so much more expensive per shirt than the arithmetic suggests.
Add an allowance rather than pretending otherwise. Something like a quarter to half a pound per screen for setup pulls, registration and reclaim is a reasonable shop figure to test against your own records — measure your consumption over a month against what this calculator predicts, and the difference is your real overhead per screen.
Ink yield and prints per pound by deposit thickness
| Deposit | Deposit (µm) | Yield (in²/oz) | Prints per pound | Typical mesh |
|---|---|---|---|---|
| 0.4 mil | 10.2 | 3,460 | 762.5 | 305 and finer |
| 0.6 mil | 15.2 | 2,307 | 508.4 | 230–305 |
| 0.8 mil | 20.3 | 1,730 | 381.3 | 200–230 |
| 1.0 mil | 25.4 | 1,384 | 305.0 | 156–200 |
| 1.2 mil | 30.5 | 1,153 | 254.2 | 110–156 |
| 1.5 mil | 38.1 | 923 | 203.3 | 86–110 |
| 2.0 mil | 50.8 | 692 | 152.5 | Coarse mesh or thick emulsion |
Yield is 1 ÷ (thickness × 0.72255) and prints per pound is 16 ÷ (72.6 ÷ yield), so both scale exactly inversely with thickness: halving the deposit doubles both. The mesh column is a shop rule of thumb, not a specification — measure your own deposit if the number matters.
How to measure your own deposit thickness
The reliable method is weighing, not gauging. Print a known area — a solid 10 × 10 in square is 100 in² — onto a substrate, weigh the substrate before and after, and divide. The mass in ounces divided by 100 in² gives you ounces per square inch, and dividing that by your ink's density in oz/in³ gives thickness in inches directly. A shop scale reading to 0.1 g is accurate enough: 100 in² at 1 mil of 1.25 g/cm³ ink is about 2.0 g, which such a scale resolves comfortably. Do it once per mesh and squeegee combination you use regularly and you will never need a rule of thumb again.
What changes the deposit, and by how much
- Mesh count. The largest single factor. Finer mesh has smaller openings and less ink volume per unit area, which is why a 305 lays down a fraction of what a 110 does.
- Emulsion over mesh thickness. A thick stencil built up with several coats sits proud of the mesh and acts as a gasket, increasing the deposit without changing the mesh.
- Squeegee durometer and angle. A soft blade at a shallow angle pushes more ink through; a hard blade held steep shears it off. Worth a substantial change in deposit on the same screen.
- Underbase. Printing white under a colour on a dark garment adds a full extra deposit, usually the heaviest one on the press. Count it as its own colour here.
- Ink type. Water-based and discharge inks lose their carrier during cure, so the wet deposit and the cured deposit differ. This calculator works in wet ink, which is what you buy and consume.
- Substrate. An open-weave or napped fabric absorbs ink that a smooth polyester surface would leave sitting on top, which raises consumption without raising the visible film.
Where ink sits in the cost of a printed garment
Ink is almost never the reason a print job costs what it does. Two cents a shirt on a large single-colour front is typical, and even a heavy four-colour job with an underbase rarely reaches a dime. What dominates is setup: separations, film, screens coated and exposed, registration on press, and the test pulls before the run is right. That cost is fixed per design, so it falls per shirt as the run grows, and it is the whole reason screen printing beats other methods on volume and loses on small orders.
Compare the alternatives on the same basis. Heat transfer vinyl has essentially no setup and a flat material cost per piece, calculated in the HTV usage calculator — usually well over a dollar for a full-front design, which is fifty times the ink cost here. Sublimation, priced with the sublimation cost calculator, sits between the two but only works on light polyester. Embroidery is priced by stitch count and machine time rather than area, which the stitch count calculator and the run time calculator handle.
Where this calculator earns its keep is purchasing and pricing at scale. Knowing that a design consumes two pounds per five hundred shirts turns an ink order from a guess into arithmetic, and knowing the yield lets you check a quote for a job you have not run yet. It also makes the mesh decision legible: moving a job from a 110 to a 200 mesh does not just sharpen the print, it cuts the ink consumed per shirt by about a third, which on a very large run is real money.