Two suppliers quote you a TIJ cartridge. One is 19 dollars, the other is 28. The cheap one looks like the obvious answer, and for a lot of buyers the decision stops there.
But a cartridge price is not a cost. It is a numerator waiting for a denominator. A cartridge at 28 dollars that prints 42,000 acceptable characters is cheaper than a cartridge at 19 dollars that prints 20,000, and the gap is not small. Until you divide by the characters your own print job actually produces, you are comparing fuel prices between two vehicles without knowing how far either one drives.
This article sets out how to work out the cost per printed character, which variables move that number the most, and how to get your own figure from a one-hour test on your own line. The formula matters more than any published number, because no cartridge label tells you how many characters are inside it.
Table of Contents
Why the Cartridge Price Cannot Answer the Question
The conclusion is that the cartridge is not the unit of purchase — the printed character is.
A cartridge is a container of ink with a printhead attached. What you actually sell to your customer, and what your compliance record actually depends on, is a readable mark on a saleable pack. Every cartridge you buy is consumed in service of producing those marks, and a portion of every cartridge never reaches a pack at all. Some of it is lost to start-up and cleaning routines. Some of it goes onto packs that are later rejected. Some of it is left in the cartridge when the printhead degrades or the ink runs dry in a way the level sensor reports badly.
This is why the cheapest cartridge on the quotation sheet can be the most expensive one in the plant. It is also why two plants using the identical cartridge model can report completely different consumption per thousand packs: they are printing different things.
It helps to separate the two sides of the question, because they are usually discussed as if they were one.
- The supply side is how much usable ink a cartridge genuinely delivers. A nominally full cartridge may hold far less usable ink than its label suggests, through sponge retention, capillary dead volume and evaporation. Our real-capacity test of the 42 ml TIJ cartridge covers that side, including how to weigh the difference rather than trust the label.
- The demand side is how much ink your print job asks for per character. That is decided by your font height, your dot density, your code length and your line settings — not by the cartridge you bought.
Most cost arguments in this industry are actually demand-side arguments wearing supply-side clothes. The rest of this article deals with the demand side, because it is the half you control most directly and the half that is most often left out of a comparison.
The Cost per Character Formula
The conclusion is that the number you want is the cartridge price divided by the characters that survive to a saleable pack.
Written out plainly:
Cost per character = Cartridge price ÷ (Characters printed − Purge and cleaning waste − Characters on rejected packs)
Three things about that expression are worth stating explicitly, because each one is where comparisons go wrong.
First, the denominator is net, not gross. The characters a cartridge prints is not the same number as the characters that reach a customer. If your line rejects 3 percent of packs, one in thirty-three characters is already paid for and thrown away.
Second, purge and cleaning are real consumption. Every start-up cycle, every nozzle recovery routine, every shift-change prime consumes ink that prints nothing. On a line that stops and starts frequently, this can be a substantial share of the total. It is a process cost rather than an ink cost, which is exactly why the hidden costs of a coding installation tend to hide here.
Third, cost per character and cost per code are related but not interchangeable. Cost per code equals cost per character multiplied by the number of characters in the code. Buyers usually compare cost per code, and that is fine — as long as both suppliers are quoting the same code format. When one supplier’s figure assumes a six-digit date and the other assumes a twenty-character serialized code, the comparison has quietly become meaningless. Working in cost per character normalizes the format away, so you can compare the ink and then multiply by whatever your real code contains.
For a related but different question — whether a UV-curable route or a solvent route produces a cheaper acceptable pack once hardware and handling are included — our comparison of the two coding routes works through that decision. This article stays on ink consumption per character.
The Variables That Move the Number Most
The conclusion is that character size dominates everything else, and it does so by a squared relationship that surprises most buyers.
Consider what a cartridge is being asked to do. Printing a character is filling an area on the substrate with a pattern of ink droplets. For a given dot spacing, the number of droplets needed to fill a character scales with the printed area of that character. Since area scales with the square of height, doubling the character height does not double the ink per character — it roughly quadruples it, before any allowance for heavier dot settings or bolder strokes.
That single relationship explains most of the variation between plants. A plant printing a 6 mm date code and a plant printing a 12 mm bold logo are not consuming slightly different amounts of ink. They are consuming amounts that differ by roughly a factor of four for the same character count, from the same cartridge model.
| Variable | What it does to ink per character | Typical direction of change |
|---|---|---|
| Character height | Scales roughly with the square of height | Small change in height, large change in cost |
| Dot density and resolution | More droplets per unit area at higher density | Moves with the print quality requirement |
| Stroke weight and bold setting | Thicker strokes fill more area per character | Set by legibility, not by ink price |
| Character count per code | Simple linear multiplier on cost per code | Fixed by the standard or the customer |
| Start-up and purge frequency | Consumes ink that prints nothing | Rises sharply with frequent stops |
| Rejection rate | Inflates the effective denominator downward | Driven by substrate and handling, not by ink |
Where dot density is concerned, there is a genuine trade-off to manage rather than a setting to maximize. Higher resolution improves small-text legibility and scanner success, and it also increases ink consumption per character. Our explanation of what actually changes between 300 dpi and 600 dpi covers where the higher setting earns its ink and where it does not.
The practical consequence is straightforward. Before you negotiate a cartridge price, check whether you can print the required mark smaller, thinner or at a lower density without failing the reader or the standard. A 30 percent reduction in character height is worth more than most price negotiations you will ever have, and it costs nothing but a print trial.
Run the Test on Your Own Line, Not on a Specification Sheet
The conclusion is that character yield must be measured on your line, with your code, because no upstream number can predict it.
Here is a one-hour procedure that produces a defensible figure.
- Fix the print job. Use the real code, at the real font height, with the real density and weight settings, at the real line speed. Do not test with a simplified placeholder message.
- Start from a new cartridge and record its price and the batch or serial.
- Print continuously and inspect at fixed intervals with the production reader, not by eye. Record the point at which the code first fails the agreed acceptance rule.
- Log the non-printing consumption. Count start-ups, purges and cleaning cycles during the run and estimate the equivalent character count they consumed, using the supplier’s own guidance or a measured comparison.
- Log the reject rate over the same period from production records, and convert it to characters.
- Repeat on at least two cartridges. One cartridge proves an anecdote; two begin to suggest a range.
Run the calculation with the numbers your test returns. As an illustration only — these figures are invented to show the arithmetic, not to describe any real product — suppose the cartridge costs 28 and the test yields 46,000 characters before the code first fails. Purge and start-up consumption is equivalent to 2,000 characters, and the line rejects 3 percent of packs:
| Step | Illustrative figure |
|---|---|
| Gross characters printed | 46,000 |
| Less purge and cleaning waste | −2,000 |
| Less rejects at 3 percent of 44,000 | −1,320 |
| Net accepted characters | 42,680 |
| Cartridge price | 28.00 |
| Cost per accepted character | 0.00066 |
Now run the same test on a cheaper cartridge priced at 19, which yields 24,000 characters with the same 2,000 characters of purge waste but an 8 percent rejection rate:
| Step | Illustrative figure |
|---|---|
| Gross characters printed | 24,000 |
| Less purge and cleaning waste | −2,000 |
| Less rejects at 8 percent of 22,000 | −1,760 |
| Net accepted characters | 20,240 |
| Cartridge price | 19.00 |
| Cost per accepted character | 0.00094 |
The cartridge costing 47 percent more at the counter is roughly 30 percent cheaper per accepted character. That is the entire point of the exercise: the ranking reverses once the denominator is real.
Note what the illustration also shows. Part of the cheap cartridge’s disadvantage comes from its lower yield, and part comes from the higher rejection rate. Both belong in the calculation. A cartridge that prints cheaply but rejects more often has not saved anything — it has moved the cost to the packing line.
When a More Expensive Cartridge Is Actually the Cheaper One
The conclusion is that a higher price is justified only when the extra yield, reliability or rejection performance is measured, not assumed.
The arithmetic above does not prove that expensive cartridges are better. It proves that price alone cannot rank them. A more expensive cartridge earns its premium in a limited number of measurable ways:
- Higher usable yield on your specific print job, verified by the test above rather than by a claimed capacity figure.
- Lower rejection rate, which is often worth more than the ink saving, because a rejected pack carries the cost of the pack, the product, the labor and the line interruption.
- More predictable end-of-life behavior, where the level indication and the print quality degrade in a way you can plan around rather than failing between shifts.
- Fewer purge cycles, if the printhead design is more tolerant of short stops on your duty cycle.
If none of those four is measurably better, the premium is not buying you anything, and the honest answer is that the cheaper cartridge is the cheaper cartridge.
Use this sheet to close the loop:
- Fix the print job — real code, real height, real density, real speed.
- Measure gross characters to the first reader failure, on two cartridges.
- Subtract purge and cleaning equivalent characters.
- Subtract characters on rejected packs using your real rejection rate.
- Divide the cartridge price by the net figure.
- Repeat for every candidate and rank on cost per accepted character, not price.
- Re-run the test whenever font size, density, substrate or line speed changes, because every one of those moves the denominator.
If you want a second opinion on the arithmetic before you commit to a supplier, send the code format, the font height and density, the line speed, the measured character yield and the rejection rate through our contact form, and FIRSTCOLOR CODING can work through the comparison with you. If you have not yet chosen the cartridge format itself, our product range sets out the available configurations, and the sizing logic behind them is covered in our guide to 12.7 mm and 25.4 mm cartridges.
The short version: stop asking whether a cartridge is expensive. Divide its price by the accepted characters it prints on your line, and you will have an answer that survives a budget review.